<PAGE>   1

                                                                   EXHIBIT 10.18

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY BRACKETS,
HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.

     INFLUENZA VACCINE COLLABORATION AND LICENSE AND DISTRIBUTION AGREEMENT

         THIS AGREEMENT is made the 19th day of June, 1998 (hereinafter, "the
Effective Date") between CSL LIMITED, A.C.N. 051 588 348 whose head office is
situated at 45 Poplar Road, Parkville in the State of Victoria, 3052, Australia
(hereinafter, "CSL Limited") and its Affiliates in the Territory (hereinafter,
collectively referred to as "CSL") of the one part, and AVIRON of 297 North
Bernardo Avenue, Mountain View, in the State of California 94043, U.S.A.
(hereinafter referred to as "Aviron") of the other part (hereinafter referred to
together as "the Parties" or each individually as a "Party").

WHEREAS

         A. Aviron has been licensed exclusive rights to, and has developed
substantial additional proprietary rights regarding an intranasally delivered
cold adapted vaccine formulation against influenza;

         B. Aviron is engaged in the development, and when developed, the
manufacture or contract manufacture, marketing and sale of such vaccine, in
[ * ] [ * ] formulations;

         C. CSL is an Australian pharmaceutical company experienced in the
manufacture and sale of influenza vaccines;

         D. Aviron and CSL wish to enter into a collaboration to develop,
perform clinical testing of, gain regulatory approval for, and to license CSL to
market and sell, Aviron's intranasal cold adapted vaccine formulation against
influenza in Australia, New Zealand, and other associated territories in Oceania
(the "Territory," as further defined below);

         E. Contemporaneously with this Agreement, CSL will issue to Aviron
options to purchase shares of CSL capital stock in consideration for the rights
granted by Aviron herein;

         NOW THIS AGREEMENT WITNESSETH AS FOLLOWS:

1.       DEFINITIONS

         1.1 "AFFILIATE" means any corporation or business entity of which
Aviron or CSL owns directly or indirectly [ * ] or more of the assets or
outstanding stock, or any corporation which Aviron or CSL directly or indirectly
controls, or any parent corporation which owns directly or indirectly [ * ] or
more of the assets or outstanding stock of Aviron or CSL or directly or
indirectly controls Aviron or CSL.

         1.2 "ALLOWABLE EXPENSES" means those expenses incurred for a
Collaboration Product subsequent to the receipt of Regulatory Approval of the
Collaboration Product in a given country in the Territory and shall consist of:

                  (a) Cost of Goods Shipped;


------------------

[*] Confidential treatment requested.


                                       1.
<PAGE>   2

                  (b) Costs of distribution and shipping of the Collaboration
Product to distributors and customers within the Territory ("Distribution
Costs");

                  (c) Direct costs, specifically allocable to the Collaboration
Product, incurred to operate and maintain the sales force which promotes and
sells the Collaboration Product, as well as sales bulletins and other
communications, sales meetings, specialty sales forces, call reporting and other
monitoring/tracking costs, district and regional sales management and marketing
management ("Selling Expenses");

                  (d) Costs, excluding [ * ] incurred by a Party or for its
account which are specifically identifiable to the advertising and marketing of
the Collaboration Product and related [ * ] including, without limitation, 
[ * ];

                  (e) Costs associated with the [ * ];

                  (f) Post-Regulatory Approval medical and clinical trial costs,
[ * ];

                  (g) Costs of [ * ] regarding the Collaboration Product in the
Territory and costs associated with [ * ];

                  (h) Costs associated with the [ * ] used in connection with
the [ * ] of the Collaboration Product or any [ * ]; and

                  (i) [ * ].

         1.3 "AVIRON PRODUCT" means Aviron's live, intranasally delivered, cold
adapted influenza vaccine [ * ].

         1.4 "AVIRON PRODUCT MARGIN" means Net Sales of Aviron Products less all
Allowable Expenses.

         1.5 "AVIRON PRODUCT MATERIALS" means any [ * ] or any other biological
materials transferred to CSL by Aviron under this Agreement.



------------------

[*] = Confidential treatment requested.



                                       2.
<PAGE>   3


         1.6 "BRIDGING STUDIES" means those certain "bridging studies" required
to be conducted to obtain Regulatory Approval in the Territory for the Aviron
Product by demonstrating [ * ].

         1.7 "COLLABORATION" shall have the meaning ascribed in Section 2.1.

         1.8 "COLLABORATION REGULATORY DATA" means all data, information,
filings, reports and results generated by or for either Party and relating to
obtaining Regulatory Approval for the Aviron Product in the Territory, in both
raw and compiled form.

         1.9 "COLLABORATION PRODUCT" means the Aviron Product, the CSL Product
or any [ * ] CSL Product, or all three, as applicable.

         1.10 "CONTROLLED" means, with respect to any particular Intellectual
Property right or other property right, that the Party owns or has a license to
such right and has the ability to grant access, a license, or a sublicense to
such right to the other Party as provided for herein without violating an
agreement with a Third Party as of the time the Party would be first required
hereunder to grant the other Party such access, license or sublicense.

         1.11 "COST OF GOODS SHIPPED" means the cost of manufacturing, supplying
and shipping a Collaboration Product in either bulk or finished form, as the
case may be and as the Steering Committee may agree, and shall consist of (i) in
the case of products and/or services acquired from Third Parties, payments to
such Third Parties (however calculated, including, for example, charges by such
Third Parties for an allocation of overhead for production of the Collaboration
Product), and (ii) in the case of manufacturing services performed by either
Aviron or CSL, including manufacturing services in support of Third Party
manufacturing, [ * ] costs of the manufacture in bulk form or finished form, as
the case may be, plus [ * ] costs shall consist of direct material and direct
labor costs [ * ] at standard, all calculated in accordance with reasonable cost
accounting methods, consistently applied, of the Party performing the work.

                  (a) As used herein, "direct material costs" shall include the
costs incurred in [ * ].

                  (b) As used herein, "direct labor" shall include the cost of
employees engaged in direct manufacturing activities and direct or indirect
quality control and quality assurance activities who are directly employed in
the manufacture, blending, filling and/or packaging of a Collaboration Product.

                  (c) [ * ] shall include a reasonable allocation of [ * ], a
reasonable allocation of [ * ] costs, and a reasonable allocation of [ * ],
unless otherwise agreed upon by the Steering Committee. Such allocations shall
be in accordance with the reasonable cost accounting methods, consistently


------------------

[*] = Confidential treatment requested.

                                       3.
<PAGE>   4
applied, of the Party performing the work. [ * ] shall not include [ * ] costs
associated with any [ * ] used for the [ * ] or [ * ] costs not otherwise
allocable to the manufacture of the Collaboration Product, nor shall [ * ]
include costs associated with capacity not incorporated into standard unit
costs. Actual costs shall exclude costs associated with [*] to the Collaboration
Product.

                  (d) Cost of Goods Shipped shall also include [ * ] and other 
[ * ] costs (but excluding [ * ] costs).

         1.12 "CSL FIELD" means the sale of influenza vaccines for prophylactic
use in the Eligible Populations in any country in the Territory.

         1.13 "CSL [ * ] PRODUCT MARGIN" means Net Sales of CSL Products sold in
the CSL Field [ * ] during the relevant influenza season, less all Allowable
Expenses allocable to such Net Sales in the CSL Field.

         1.14 "CSL PRODUCT" means CSL's inactivated, injectable influenza
vaccine product, for use in the CSL Field.

         1.15 "DEVELOPMENT AND REGULATORY COSTS" means the costs incurred by
either Party or for its account specifically identifiable to the development of
the Aviron Product for Regulatory Approval in the Territory and shall consist of
(i) [ * ] costs associated with the conduct of the [ * ]; (ii) Cost of Goods
Shipped of any Aviron Product [ * ]; and (iii) direct labor and materials and
out-of-pocket costs associated with the [ * ] in the Territory all as specified
in the Development Plan and approved by the Steering Committee, all calculated
in accordance with reasonable cost accounting methods, consistently applied by
the Party performing the work.

         1.16 "DEVELOPMENT PLAN" means the plan for the clinical development of
the Aviron Product created by the Steering Committee pursuant to Section 4.1.

         1.17 "ELIGIBLE POPULATIONS" means any population group which is other
than the following: [ * ].

         1.18 "FDA" means the United States Food and Drug Administration or any
successor agency.

         1.19 "[ * ] AVIRON PRODUCT" means Aviron's live, intranasally
delivered, cold-adapted influenza vaccine [ * ].


------------------

[*] Certain information in this document has been omitted and filed separately 
    with the Commission. Confidential treatment has been requested with respect
    to the omitted portions, which are marked by an "*" in the text.



                                       4.
<PAGE>   5
         1.20 "[ * ] CSL PRODUCT" means any influenza vaccine (whether live or
killed) product [ * ].

         1.21 [ * ] CSL PRODUCT MARGINS" means Net Sales of [ * ] CSL Products
in the CSL Field less all Allowable Expenses.

         1.22 "INCREMENTAL STUDIES" means all clinical trials necessary for
Regulatory Approval in the Territory over and above those described and cited in
the PLA, including the Bridging Studies.

         1.23 "INTELLECTUAL PROPERTY" means, as applicable, Aviron Intellectual
Property, CSL Intellectual Property or Joint Intellectual Property.

                  (a) "AVIRON INTELLECTUAL PROPERTY" means any and all Know-How,
techniques, inventions, improvements and/or discoveries, or materials (including
the Aviron Product Materials), whether or not patentable or subject to copyright
or trademark protection and in whatever form kept, covering the development,
manufacture, use or sale of the Aviron Product and which are Controlled by
Aviron as of the Effective Date, or developed or made solely by or for Aviron or
which come under the Control of Aviron during the term of this Agreement and
developed other than pursuant to this Agreement.

                  (b) "CSL INTELLECTUAL PROPERTY" means any and all Know-How,
techniques, inventions, improvements and/or discoveries, or materials, whether
or not patentable or subject to copyright or trademark protection and in
whatever form kept, relating to or useful for the development, manufacture, use
or sale of the Aviron Product, and which are Controlled by CSL as of the
Effective Date, or which are developed or made solely by or for CSL or which
come under the Control of CSL during the term of this Agreement, and developed
other than pursuant to this Agreement.

                  (c) "JOINT INTELLECTUAL PROPERTY" means any and all Know-How,
materials, techniques, inventions, improvements and/or discoveries whether or
not patentable or subject to copyright or trademark protection and in whatever
form kept, covering the development, manufacture, use or sale of the Aviron
Product which are developed or made by either or both Parties pursuant to and
during the term of this Agreement, regardless of inventorship.

         1.24 "KNOW-HOW" means all information, data, techniques and inventions
not generally known which are necessary for researching, developing, using,
manufacturing, marketing or selling the Aviron Product.

         1.25 "MARKET LAUNCH" means the first commercial sale of the Aviron
Product in the Territory by CSL or its Affiliate.

         1.26 "MICHIGAN" means the Regents of the University of Michigan, a
constitutional corporation of the State of Michigan with offices located at
Wolverine Tower, Room 2071, 3003 South State Street, Ann Arbor, Michigan,
48109-1280, USA.


------------------

[*] = Confidential treatment requested.


                                       5.
<PAGE>   6
         1.27 "MICHIGAN AGREEMENT" means the Materials Transfer and Intellectual
Property Agreement between Aviron and Michigan dated February 24, 1995, as
amended and attached hereto as Schedule 1.22.

         1.28 "NET SALES" shall mean the sum, over the term of this Agreement,
of all amounts actually received and all other consideration actually received
(or, when in a form other than cash or its equivalent, the fair market value
thereof when received) by CSL and its Affiliates from persons or entities due to
or by reason of the sale, distribution or use of Collaboration Products, less
the following deductions and offsets, but only to the extent such sums are
otherwise included in the computation of Net Sales, or are paid by CSL and its
Affiliates and not otherwise reimbursed:

                  (a) refunds, rebates, replacements or credits actually allowed
and taken by purchasers for return of Collaboration Products;

                  (b) government-mandated rebates or refunds given by CSL or its
Affiliates for purchases of customary trade, quantity and cash discounts
actually allowed and taken;

                  (c) excise, value-added, transportation, use and sales taxes
actually paid by CSL and its Affiliates for Collaboration Products; and

                  (d) shipping and handling charges actually paid by CSL and its
Affiliates for Collaboration Products.

         Sales of Collaboration Products intended for resale to Third Parties,
and made internally amongst CSL and its Affiliates or sublicensees shall not be
deemed sales for purposes of calculating "Net Sales" subject to royalty pursuant
to Sections 9.2 and 10.3 of this Agreement (note that the resale by the
recipient shall be included in the calculation of "Net Sales" and subject to
royalties). Whenever the term "Collaboration Product" may apply to a
Collaboration Product during various stages of manufacture, use or sale, "Net
Sales," as otherwise defined, shall be derived from the sale, distribution or
use of such Collaboration Product by CSL or its Affiliates at the stage of its
highest invoiced value to Third Parties.

         1.29 "PBAC" means the Pharmaceutical Benefits Advisory Committee of
Australia and any corresponding agency in any other country in the Territory.

         1.30 "PBS LISTING" means listing of a product on the Schedule of
Pharmaceutical Benefits by the Australian Commonwealth Department of Health or
the equivalent in any other country in the Territory.

         1.31 "PLA" means both the Product Licensing Application and the
Establishment Licensing Application for the [ * ] Aviron Product, Controlled by
Aviron and to be filed with the FDA by Aviron following the Effective Date.


------------------

[*] = Confidential treatment requested.

                                       6.
<PAGE>   7

         1.32 "REGULATORY APPROVAL" means the necessary approval which must be
received from the relevant governmental regulatory authority in a given country
in the Territory (e.g. in Australia, the TGA) before the Aviron Product may be
commercially sold in any such country.

         1.33 "STEERING COMMITTEE" means the Committee established pursuant to
Article 3 herein.

         1.34 "TGA" means the Therapeutic Goods Administration of Australia and
any corresponding agency in any other country in the Territory.

         1.35 "TERRITORY" means Australia and New Zealand and their territories,
Fiji, Papua New Guinea, Vanuatu, Tonga, the Solomon Islands and the Cook
Islands.

         1.36 "THIRD PARTY" means any party besides the Parties and their
respective Affiliates.

2.       NATURE AND SCOPE OF THE COLLABORATION

         2.1 SCOPE OF THE COLLABORATION. The Parties intend to establish a
collaboration pursuant to which the Parties will jointly conduct the necessary
clinical development of the Aviron Product for Regulatory Approval in the
Territory, as set forth in the Development Plan described in Section 4.1. CSL
will then market, promote, sell and distribute the Aviron Product in the
Territory as set forth in the Marketing Plan described in Section 5.1. The
collaboration described in this Section 2.1 (the "Collaboration") will be
overseen by the Steering Committee, pursuant to Section 3.1.

         2.2 DILIGENT EFFORTS. The Parties will use diligent efforts and
cooperate with one another in carrying out their respective obligations
hereunder and as set forth further in the Development Plan and the Marketing
Plan.

3.       MANAGEMENT OF THE COLLABORATION

         3.1 STEERING COMMITTEE. Immediately following the Effective Date, the
Parties shall establish and maintain a Steering Committee which will (a) decide
on strategic issues and policies; (b) monitor the conduct, management and
supervision of the Collaboration, and (c) create and implement the Development
Plan and the Marketing Plan.

                  (a) MEMBERS. The Steering Committee shall be composed of an
equal number of representatives of CSL and of Aviron. The initial number of
Steering Committee members shall be four (4), and may be increased to six (6) by
written agreement of the Parties. The representatives of the Steering Committee
shall consist of individuals with the appropriate skills necessary to deal with
the issues before them, with each Party having the right to change its
representatives from time to time by notifying one another to this effect. The
first representatives of the Steering Committee to be nominated by CSL and
Aviron shall be set forth in Schedule 3.1 hereto.

                  (b) MEETINGS. The Steering Committee shall meet at least twice
per year to decide on strategic issues and policies, in person or via
teleconference or videoconference, and shall hold such additional meetings as
its members think fit. Each member of the Steering 


                                       7.
<PAGE>   8

Committee may appoint an alternate, and references in this article to "members"
and "representatives" of the Steering Committee shall include references to
alternates of such members and representatives. An alternate will only act if
the member is not available.

                  (c) CHAIRPERSON. Unless otherwise agreed by the Parties, the
Chairperson for the Steering Committee shall alternate between Aviron and CSL at
each meeting, commencing with Aviron. The Chairperson shall appoint a Secretary
from amongst the members of the Steering Committee who shall be responsible for
preparing the minutes of meetings as well as any related correspondence.

                  (d) QUORUM. No business shall be transacted at any meeting of
the Steering Committee unless a quorum of members is present at the time when
the meeting proceeds to business. A quorum shall be at least four (4) members
present in person or by their alternate, two (2) of whom must be representatives
appointed by CSL and two (2) representatives appointed by Aviron.

                  (e) MINUTES. Minutes of resolutions and other proceedings of
the Steering Committee shall be taken and maintained in an appropriate manner.
Minutes shall be signed by a member of each of the Parties present at the
proceedings which took place. Any minutes so signed will be prima facie evidence
of the resolutions from proceedings to which they relate.

                  (f) RESOLUTIONS. All matters and formal resolutions of the
Steering Committee shall require unanimous approval.

                  (g) DISAGREEMENT. In the event of any disagreement amongst
members of the Steering Committee with respect to any aspect of the
Collaboration which remains unresolved for a period of seven (7) days, the
matter of disagreement shall be referred to the Chief Executive Officer of
Aviron and the General Manager of the Pharmaceutical Division of CSL for good
faith resolution. In the event they cannot resolve such matter to their mutual
satisfaction within thirty (30) days, the matter shall be referred to
non-binding mediation as follows: Upon expiration of such thirty (30) day
period, each Party shall have the right to notify the other Party of its desire
to enter into non-binding mediation for a period not to exceed ninety (90) days,
to be conducted by an unrelated Third Party mutually agreed upon, possessing the
appropriate skills, expertise and experience to address the issue in dispute.
Such mediator shall promptly deliver to the Parties a written recommendation.
All costs of such mediation shall be shared equally by the Parties. If such
dispute nonetheless remains unresolved, Article 19.8 shall apply.

         3.2 LIAISONS. Each Party shall each appoint a liaison, who may be a
member of the Steering Committee, who shall report to the Steering Committee as
required and will coordinate communications between such Party and the Steering
Committee and the other Party.

         3.3 GENERAL RESPONSIBILITIES OF STEERING COMMITTEE.

                  (a) To coordinate the preparation of and adopt the Development
Plan;

                  (b) to exchange and mutually share data and reports generated
from all clinical trials of the Aviron Product to the extent such data may
assist the Parties in fulfilling their obligations herein;



                                       8.
<PAGE>   9

                  (c) to discuss and agree on procedures for whatever data
handling and analysis CSL is required to provide for Regulatory Approval;

                  (d) in accordance with mutually agreed practice which is in
compliance with government regulations, to promptly inform each other of any
adverse events arising out of such studies and, if necessary, to meet to decide
on a course of action, including the undertaking of any voluntary recall;

                  (e) to keep each other informed on the progress toward
Regulatory Approval and PBS Listing;

                  (f) to coordinate the preparation of the Marketing Plan; and

                  (g) to determine an appropriate manufacturing and supply
strategy for the Aviron Product, as set forth in Article 6.

                  (h) to determine the need for and oversee the conduct of any
post-Regulatory Approval clinical trials of the Aviron Product for the
Territory.

         3.4 SUBCOMMITTEES. The Steering Committee shall have the authority to
establish subcommittees to carry out one or more of its responsibilities
hereunder.

         3.5 DOCUMENTATION. The Steering Committee shall ensure that great care
is taken to properly record and document all activities performed during the
Collaboration. Where reasonably practicable the Parties shall agree and observe
uniform and consistent practices and standards in relation to the recording and
documentation of such activities.

4.       DEVELOPMENT OF AVIRON PRODUCT

         4.1 DEVELOPMENT PLAN. Immediately following its establishment, the
Steering Committee shall discuss and agree on details for (a) conducting the
Incremental Studies, including the development of the requisite protocols and
any changes or additions thereto; (b) coordinating the Parties' activities and
responsibilities in conducting the Incremental Studies and monitoring their
progress; (c) coordinating the filings necessary for Regulatory Approval; and
(d) creating a budget for the aforementioned activities (collectively, the
"Development Plan"). The general outline of the Incremental Studies component of
the Development Plan is set forth in Schedule 4.1. The Steering Committee may
recommend use of a contract research organization to carry out any of the
activities necessary to obtaining Regulatory Approval for the Aviron Product,
but Aviron shall have the final approval as to the use of such contract research
organization. The Steering Committee will update and amend the Development Plan
from time to time. In addition to the obligations set forth in the Development
Plan, the Parties shall have the rights and responsibilities set forth in
Sections 4.2 and 4.3.

         4.2 CSL DEVELOPMENT RIGHTS AND RESPONSIBILITIES.

                  (a) PLA. CSL will have the right to review, use and reference
the PLA for the purpose of obtaining Regulatory Approval and PBS Listing of the
Aviron Product.



                                       9.
<PAGE>   10

                  (b) INCREMENTAL STUDIES. CSL will make an initial
determination of, and report to the Steering Committee about, all those clinical
trials which comprise the Incremental Studies, other than the Bridging Studies.
The Steering Committee shall make the final determination as to all such
necessary Incremental Studies.

                  (c) REGULATORY FILINGS. CSL will, under the direction of the
Steering Committee and in close coordination with Aviron, prepare and file all
applications for Regulatory Approval and for PBS Listing or any other pricing or
reimbursement approval for the Aviron Product in the Territory. CSL shall be the
sponsor of all such filings for such Regulatory Approvals. Aviron shall have the
right to receive copies of, and an irrevocable right of reference to, all
submissions for Regulatory Approval and for PBS Listing or any other pricing or
reimbursement approval for the Aviron Product in the Territory.

         4.3 AVIRON DEVELOPMENT RIGHTS AND RESPONSIBILITIES.

                  (a) SUPPLY OF AVIRON PRODUCT. Aviron will use its diligent
efforts to supply, or cause to be supplied, all necessary Aviron Product for the
conduct of the Incremental Studies as determined by the Steering Committee. 
[ * ]

                  (b) BRIDGING STUDIES. Aviron shall retain the ultimate
decision making power as regards the Bridging Studies.

                  (c) USE AND OWNERSHIP OF COLLABORATION REGULATORY DATA. CSL
agrees that all Collaboration Regulatory Data generated by CSL or its
Affiliates, consultants or contractors shall be the property of Aviron and may
be used by Aviron, its Affiliates and its sublicensees free of charge in
furtherance of applications for regulatory approval of the Aviron Product for
use, sale or distribution outside the Territory, and that CSL shall reasonably
cooperate with Aviron, its Affiliates and its sublicensees in providing such
Collaboration Regulatory Data and in executing any necessary instruments or
documents.

         4.4 DEVELOPMENT AND REGULATORY COSTS. Each Party shall bear its own
Development and Regulatory Costs incurred by it, subject to reimbursement as
provided herein. On a [ * ] basis, [ * ] shall invoice [ * ] for [ * ] of the
Development and Regulatory Costs incurred by [ * ]. Such payment shall be due
within [ * ] of receipt of such invoice.

         4.5 CONDUCT OF DEVELOPMENT. Each Party agrees to use diligent efforts
to obtain Regulatory Approval for the Aviron Product in the Territory. Each
Party shall ensure that its tasks assigned under the Development Plan are
carried out adhering to the highest ethical and safety standards. The Parties
agree to comply with all current Good Clinical Practices of the FDA (or their
equivalent in the Territory).

         4.6 CONDUCT OF TRIALS OTHER THAN INCREMENTAL STUDIES. In the event
Aviron desires to conduct clinical trials or other testing of the Aviron Product
in the Territory under this Agreement which are not required to obtain or
maintain Regulatory Approval in the Territory, Aviron shall [ * ].


------------------

[*] Certain information in this document has been omitted and filed separately 
    with the Commission. Confidential treatment has been requested with respect
    to the omitted portions, which are marked by an "*" in the text.

                                      10.
<PAGE>   11

         4.7 THIRD PARTY TECHNOLOGY. If either Party becomes aware of any Third
Party technology which is useful or necessary to the development, manufacture,
use or sale of the Aviron Product in the Territory, it shall promptly notify the
other Party. The Steering Committee shall then determine whether it would be
advantageous for either CSL or Aviron to obtain a license to or otherwise
acquire such Third Party technology, provided that such license or other
acquisition of such technology shall only occur with the prior written consent
of both Parties to the economic terms of such license or acquisition.

5.       MARKETING AND PROMOTION OF AVIRON PRODUCTS

         5.1 MARKETING PLAN. CSL will generate, and the Steering Committee will
approve a plan, to be updated at least annually, regarding CSL's efforts to
market, promote, sell and distribute Collaboration Products (the "Marketing
Plan"). The Marketing Plan will include, without limitation, [ * ].

         5.2 PRICING POLICIES. The Steering Committee shall determine all
pricing policies for the Aviron Product, with the objective of optimizing the
financial returns to each Party, but CSL shall otherwise have the absolute
unilateral right to determine the prices at which CSL will sell the Aviron
Product in the Territory and to [ * ] provided that CSL will prepare [ * ] and
seek to secure [ * ] having regard always for [ * ].

         5.3 MARKET RESEARCH. CSL shall be responsible for any market research
necessary to confirm the targeted indications of the Aviron Product, markets and
marketing platforms within the Territory.

         5.4 MARKETING MATERIALS. Aviron will provide to CSL, to the extent that
Aviron has a right to do so, access to any photographs, templates, or other
promotional materials, etc., used in the production of marketing materials where
such materials may be adapted for use in the Territory [ * ].

         5.5 CSL'S DUTIES AND OBLIGATIONS. CSL shall during the term of this
Agreement:

                  (a) Use its diligent endeavors to market, promote, extend and
maximize the sales of the Aviron Product throughout the Territory, which shall
include without limitation, the promotion and marketing activities described in
the Marketing Plan;

                  (b) Give proper consideration and weight to the interests of
Aviron in all dealings;

                  (c) Not make any representations or give any warranties or
other benefits in favor of any proposed purchasers of the Aviron Product or to
the detriment of Aviron beyond those consistent with the relevant Regulatory
Approval.

                  (d) Comply with all laws, ordinances, regulations, rules and
administrative directions applicable to, governing or controlling the
importation of the Aviron Products into, and the manufacture, sale and use of
the Aviron Product in, the Territory;


------------------

[*] = Confidential treatment requested.

                                      11.
<PAGE>   12

                  (e) As and when requested, provide to the Steering Committee
reports as to sales, stock levels, market trends, and marketing difficulties and
opportunities;

                  (f) Promptly inform Aviron of any material facts or opinions
likely to be relevant in relation to the marketing of the Aviron Product and in
particular of any infringements or possible infringements of any of Aviron
Intellectual Property or Joint Intellectual Property; and

                  (g) Ensure that its employees, agents and dealers are
acquainted with and bound by the obligations imposed by this Article 5.

         5.6 CSL COVENANTS.

                  (a) CSL shall not sell the Aviron Product outside the
Territory or sell the Aviron Product to a Third Party within the Territory where
there are reasonable grounds for CSL to believe that the Third Party may,
whether directly or indirectly, sell or cause to be sold the Aviron Product
outside the Territory.

                  (b) CSL Limited hereby guarantees the performance of all
obligations under this Agreement undertaken by its Affiliates.

         5.7 FLUMIST(TM) TRADE MARK; CSL LOGO. It is the Parties' intention to
use Aviron's FluMist(TM) trade mark as the sole trade mark for the promotion and
marketing of the Aviron Product in the Territory, unless otherwise determined by
the Steering Committee, except that CSL shall be entitled to use its corporate
logo on any labeling of the Aviron Product, provided that CSL's corporate logo
is in a form, position and size previously agreed to in writing by Aviron.
Aviron undertakes not to appropriate in any way any of CSL's intellectual
property rights covering, or relating to CSL's logo. CSL shall not use in its
business any other trade marks which are similar or substantially similar to or
so nearly resemble the Trade Marks so as to be likely to cause deception or
confusion.

6.       COMMERCIAL SUPPLY OF AVIRON PRODUCT

         6.1 SUPPLY STRATEGY.

                  (a) SUPPLY BY AVIRON. It is Aviron's intention to supply, or
cause to be supplied, finished Aviron Product to CSL for sale in the Territory.
Any such supply shall be pursuant to a separate supply agreement. Such supply
agreement will contain standard industry terms, including without limitation
provisions regarding forecasts, ordering, delivery and acceptance. Aviron
Product provided to CSL pursuant to such supply agreement will be invoiced to
CSL at Aviron's [ * ], which [ * ] shall not be [ * ] Such agreement will also
provide that: (i) Aviron shall in good faith attempt to meet CSL's Aviron
Product requirements, provided that in the event that [ * ], Aviron reserves the
right to [ * ]; (ii) Aviron would not be held liable for [ * ]; and (iii) that
such Aviron Product

------------------

[*] = Confidential treatment requested.


                                      12.
<PAGE>   13

would be manufactured in accordance with the specifications approved by the TGA
and in compliance with Good Manufacturing Practices.

                  (b) ALTERNATIVE STRATEGIES. If Aviron is restrained by any act
of the U.S. government from supplying or, [ * ], Aviron Product to CSL, then the
Parties, through the Steering Committee, shall determine an alternative strategy
for supplying CSL with its requirements for Aviron Product for sale in the
Territory. Such alternative strategy may included the manufacture by CSL, or by
a Third Party recommended by CSL, of either bulk or finished Aviron Product for
sale in the Territory.

                  (c) PAYMENT. CSL shall pay Aviron for such Aviron Product
supplied under this Section 6.1 within [ * ] days of receipt of invoice.

7.       LICENSE GRANT

         7.1 AVIRON LICENSE GRANT. Subject to the terms of this Agreement,
Aviron hereby grants to CSL an exclusive license under the Aviron Intellectual
Property and Aviron's interest the Joint Intellectual Property, and an exclusive
sublicense under the Michigan Agreement, to develop, use, offer for sale, sell
or otherwise distribute the Aviron Product in the Territory, subject to Section
7.2. In the event that the Steering Committee determines under Article 6 that
CSL shall manufacture Aviron Product, Aviron shall also grant to CSL a license
to manufacture Aviron Product for sale in the Territory.

         7.2 AVIRON RETAINED RIGHTS. Aviron retains such rights under the
license granted in Section 7.1 as are necessary or useful to Aviron's
performance of its obligations under this Agreement.

         7.3 CSL LICENSE GRANT. Subject to the terms of this Agreement, CSL
hereby grants to Aviron [ * ] license, under the CSL Intellectual Property and
CSL's interest in the Joint Intellectual Property, to develop, use, offer for
sale, sell or otherwise distribute the Aviron Product outside the Territory,
including the right to sublicense.

         7.4 MICHIGAN RETAINED RIGHTS. The license granted under Section 7.1 is
subject at all times to the Michigan Agreement, as further set forth in Article
10, including the [ * ].

         7.5 AVIRON COVENANTS.

                  (a) Aviron agrees not to appoint any other person to act as
its distributor, licensee or sublicensee for sale of the Aviron Product in the
Territory during the term of this Agreement, except that for [ * ].


------------------

[*] = Confidential treatment requested.



                                      13.
<PAGE>   14
                  (b) For the duration of CSL's exclusive rights in the
Territory granted hereunder, Aviron undertakes not to sell the Aviron Product to
any person, company or firm residing or trading in the Territory, and not to
sell or otherwise provide the Aviron Product to any person, company or firm
residing or trading outside the Territory which Aviron has reasonable grounds to
believe is purchasing or obtaining the Aviron Product for the purpose of
manufacturing or marketing the Aviron Product in the Territory.

         7.6 LIMITATIONS ON USE OF [ * ] During the term of the Agreement, CSL
will have no rights to use the [ * ] except with respect to the development,
manufacture, use or sale of the Aviron Product or any Collaboration Product in
the Territory, and will have no right to [ * ].

         7.7 OPTIONS FOR CSL STOCK. In consideration of the license granted
herein, CSL agrees to issue to Aviron three options to purchase, in the
aggregate, one million (1,000,000) shares of CSL Limited Common Stock as
described in the Option Agreement effective as of even date and attached and
incorporated into this Agreement as Schedule 7.7 hereto.

8.       FLUMIST(TM) TRADE MARK

         8.1 OWNERSHIP. CSL hereby acknowledges and agrees that Aviron is the
sole owner of the FluMist(TM) trade mark, and that CSL has no interest in the
FluMist trade mark other than the license granted in Section 8.2 below.

         8.2 LICENSE GRANT. Subject to the limitations set forth below, Aviron
hereby grants to CSL [ * ] license to use the FluMist trade mark solely in
connection with CSL's marketing, promotion and distribution of Aviron Product in
the Territory under this Agreement and pursuant to the license granted under
Section 7.1.

         8.3 FORM OF USE. CSL shall use the FluMist trademark only in the forms
approved in writing by Aviron, and shall include where appropriate the
designations (R) or (TM) and a statement that the FluMist trade mark is the
trade mark of Aviron, and other proprietary notices as are reasonably required
by Aviron from time to time.

         8.4 NO CONTEST. CSL agrees that it will not contest, oppose or
challenge Aviron's ownership of the FluMist trade mark. In particular, CSL will
not register or attempt to register the FluMist trade mark in any jurisdiction
nor oppose Aviron's registration of the FluMist trade mark, alone or with other
words or designs, in any jurisdiction. If CSL uses, registers or applies to
register a licensed mark that violates its obligations under this Section 8.4,
CSL agrees, at Aviron's request, to abandon the use of any such mark and any
application or registration for such mark.

         8.5 QUALITY CONTROL. The nature and quality of all goods sold by CSL in
connection with the FluMist trade mark and all advertising and promotional uses
and all other related uses of the FluMist trade mark by CSL shall conform to
Aviron's standards. CSL will provide samples of advertising and other
promotional material relating to the marketing, sale or distribution of 



------------------

[*] = Confidential treatment requested.

                                      14.
<PAGE>   15
Aviron Product in the Territory to Aviron for approval at least [ * ] days
before such materials are to be distributed, displayed or otherwise used. CSL
will not distribute, display or otherwise use such materials without Aviron's
prior written approval, not to be unreasonably withheld.

         8.6 CONFUSINGLY SIMILAR AND/OR COMBINATION MARKS. Except as provided in
Section 5.7, CSL agrees not to adopt or use any other trade marks, words,
symbols, letters, designs or marks (a) in combination with Aviron's FluMist
trade mark in a manner which would create combination marks, or (b) that would
be confusingly similar to the FluMist trade mark, provided that CSL may use the
FluMist trade mark with other marks or names if such other marks or names are
sufficiently distinctive to avoid the consumer impression that such other marks
or their owners are associate with Aviron. Notwithstanding the foregoing, Aviron
acknowledges that CSL currently possesses and uses the trademarks "FLUVAX" and
"FLUMAX."

         8.7 REGISTRATION COSTS. Aviron shall be responsible for the payment of
any and all costs relating to registration of the FluMist trade mark in the
Territory, provided that such costs will be deemed to be [ * ].

         8.8 INFRINGEMENT. In the event that either Party becomes aware that a
Third Party is infringing upon the FluMist trade mark, it shall promptly notify
the other Party in writing. [ * ] shall have the initial right to institute
legal proceedings against such Third Party, which proceedings shall be at [ * ]
expense. [ * ] shall render all reasonable assistance to [ * ] in the
prosecution of such proceedings as and when requested by [ * ] Should [ * ]
elect not to institute proceedings against such Third Party, [ * ] shall than be
entitled to institute proceedings in its own name. [ * ].

9.       DETERMINATION AND ALLOCATION OF PROFITS

         9.1 REIMBURSEMENT OF ALLOWABLE EXPENSES. CSL will be reimbursed for its
Allowable Expenses from the Net Sales of Collaboration Products. CSL will
reimburse Aviron for all of Aviron's Allowable Expenses from Net Sales of Aviron
Product, as invoiced, within fifteen (15) days following the conclusion of each
calendar quarter. For the avoidance of doubt, it is understood that the [ * ].

         9.2 AVIRON ROYALTIES. Following Market Launch of the Aviron Product in
the Territory and during the remaining term of the Agreement, CSL shall pay the
following royalties to Aviron:

                  (a) [ * ] of the Aviron Product Margin;

                  (b) [ * ] of the CSL [ * ] Product Margin; and

                  (c) [ * ] of the CSL [ * ] Product Margin.

------------------

[*] = Confidential treatment requested.


                                      15.
<PAGE>   16
         9.3 PAYMENT; REIMBURSEMENT. CSL shall pay to Aviron all amounts owed
under Sections 9.1, 9.2 and 10.3 accruing for each calendar quarter within
thirty (30) days following the conclusion of such calendar quarter. Such
payments shall be accompanied by a report detailing Net Sales of each
Collaboration Product and all Allowable Expenses deducted therefrom.

         9.4 RECORDS AND AUDITS. CSL shall maintain documentation pertaining to
the calculation of payments outlined in Section 9.1, 9.2 and 10.3 for four (4)
years. Aviron shall at its cost have a right to annually appoint an independent
auditor reasonably acceptable to CSL to verify that payments made pursuant to
this Article 9 have been made in accordance with the terms of this Agreement.
Aviron shall give CSL not less than sixty (60) days prior written notice of each
such appointment. CSL shall promptly make up any discrepancy, including interest
assessed at the lesser of (a) an interest rate of one percent (1%) per month, or
(b) the highest interest rate amount allowed by law. In the event that such
auditor determines that there is a discrepancy of greater than five percent (5%)
between the amount owed and the amount paid to Aviron, CSL shall bear the cost
of such audit. This Section 9.4 shall survive termination or expiry of this
Agreement for four (4) years.

         9.5 CURRENCY. All payments required to be made pursuant to this
Agreement shall be calculated in [ * ] unless otherwise agreed in writing
between the Parties, and the royalties owed under Sections 9.2 and 10.3 shall be
calculated using the exchange rates [ * ] on the last day of each relevant 
[ * ].

         9.6 WITHHOLDING OF TAXES. Aviron acknowledges and agrees that CSL shall
have the right and obligation to withhold any and all taxes due in the
Territory, if any, arising from the royalty payments made by CSL to Aviron under
Section 9.2. CSL agrees to use good faith commercially reasonable efforts to
minimize any such withholding or other taxes assessed on such payments in the
Territory. CSL shall pay all such taxes to the appropriate tax authority on
Aviron's behalf in compliance with all applicable laws, regulations and rules of
the relevant jurisdiction in the Territory, and shall secure and provide to
Aviron proof of any such withholding of taxes paid by CSL for the benefit of
Aviron.

10.      MICHIGAN LICENSE

         10.1 SUBLICENSE LIMITATION. CSL acknowledges the existence of Aviron's
license under the Michigan Agreement and acknowledges and accepts that Aviron
may only grant to CSL such rights as Aviron is permitted to grant pursuant to
the Michigan Agreement.

         10.2 CSL OBLIGATIONS. CSL accepts that the following provisions of the
Michigan Agreement are hereby incorporated by reference and shall be binding
upon CSL as a sublicensee under the Michigan Agreement (as defined in Section
2.6 of the Michigan Agreement):

                  (a) Article 4 (obligations and restrictions relating to Master
Strains (as defined in Section 2.6 of the Michigan Agreement), products and
their ownership and use);

                  (b) Section 6.2 (duties of use of a nomenclature system);

                  (c) Section 6.3 (duties to keep records and rights of
inspection);


---------

[ * ] = Confidential treatment requested.


                                      16.
<PAGE>   17
                  (d) Article 9 (obligations regarding the periodic reporting,
disclosure and grant of rights to certain intellectual property);

                  (e) Section 13.4 (duties to avoid improper representations or
responsibilities);

                  (f) Article 14 (obligations to defend, hold harmless and
indemnify Michigan);

                  (g) Section 14.3 (obligations to retain insurance), as further
specified in Section 10.7 of this Agreement;

                  (h) Section 15.2 (survival of certain obligations);

                  (i) Section 15.5 (obligations relating to the return and
non-use of Master Strains and certain intellectual property and prohibition on
the manufacture of products after termination of the Michigan Agreement);

                  (j) Section 15.6 (duties to provide rights to Michigan to
certain intellectual property upon termination of the Michigan Agreement);

                  (k) Articles 16 and 17 (duties relating to confidential
information and to pre-publication disclosure);

                  (l) Article 20 (duties to control export); and

                  (m) Article 22 (duty to restrict use of Michigan's name).

         10.3 MICHIGAN ROYALTY. In addition to the amounts to be paid to Aviron
pursuant to Section 9.2, CSL shall pay Aviron a royalty equal to [ * ] of all 
[ * ] in the Territory. The royalty owed under this Section 10.3 and all
calculations pertaining thereto shall be separately identified on the report
provided to Aviron under Section 9.3. Such royalty paid to Aviron under this
Section 10.3 shall [ * ].

         10.4 USE OF AVIRON PRODUCT MATERIALS. CSL acknowledges and agrees that
the Aviron Product Materials are confidential materials of Aviron and Michigan
and that access to the Aviron Product Materials shall be limited to those of its
employees reasonably requiring such access for the purposes set forth in this
Agreement, who further will be required, in writing, to treat the Aviron Product
Materials as confidential. In addition, CSL agrees that in the event
cold-adapted influenza virus strains other than the Aviron Product Materials
come into its possession, it will not transfer such other virus strains to any
Third Party without the consent of Aviron.

         10.5 WARRANTY DISCLAIMER. CSL acknowledges Michigan's warranty
disclaimer and limitation of liability contained in the Michigan Agreement, and
will make no statements, representations or warranties inconsistent with such
warranty disclaimer or limitation of liability.


------------------

[*] = Confidential treatment requested.

                                      17.
<PAGE>   18
         10.6 SUBLICENSE TERMINATION. The sublicense granted to CSL by Aviron
under the Michigan Agreement shall terminate upon termination of the Michigan
Agreement, unless assignment of the sublicense to Michigan is accepted in
writing by CSL and Michigan. Upon termination of the Michigan Agreement, CSL
shall have the option to enter into good faith negotiations with Michigan for
such assignment.

         10.7 INSURANCE. Prior to any distribution of Aviron Product by CSL in
the Territory, CSL shall obtain and maintain in effect a product liability
insurance policy providing reasonable coverage for all claims with respect to
such distribution. CSL shall furnish Aviron with a certificate of currency of
such insurance upon request.

         10.8 COOPERATION. CSL agrees to cooperate reasonably with Aviron in
assisting it to comply with its obligations under the Michigan Agreement as it
pertains to Aviron Products sold by CSL and Affiliates under this Agreement.

11.      PROVISION OF TECHNICAL INFORMATION

         11.1 AVIRON INTELLECTUAL PROPERTY. Aviron shall make available to CSL,
for performance of this Agreement only, the Aviron Intellectual Property which
Aviron has in, or which comes into, its possession and which Aviron considers to
be relevant to the reasonable needs of CSL in discharging its obligations
hereunder, but only to the extent to which Aviron has, or is readily able to
obtain, the right to divulge such information to CSL for such purpose.

         11.2 CSL RIGHTS. CSL shall have the right, during the term of this
Agreement and pursuant to the terms of its license under Section 7.1, to use any
Aviron Intellectual Property made available to it by Aviron pursuant to Section
11.1 and/or Joint Intellectual Property for the proper discharge by CSL of its
obligations hereunder but not otherwise, PROVIDED HOWEVER that nothing in this
Section 11.2, express or implied, shall give CSL the right to use any of the
Aviron Intellectual Property made available to it by Aviron pursuant to Section
11.1 for any purpose whatsoever after the termination of this Agreement.

12.      INTELLECTUAL PROPERTY RIGHTS

         12.1 OWNERSHIP. CSL recognizes and acknowledges that all rights in the
Aviron Intellectual Property, including but not limited to all patents in
respect of the Aviron Product contained therein, are the exclusive property of
Aviron and Michigan. During the term of the Agreement, the Joint Intellectual
Property shall be [ * ] and thereafter the provisions of Sections 12.4(b) and
18.3(g) shall apply.

         12.2 INFRINGEMENT BY THIRD PARTY. In the event that a Party becomes
aware that a Third Party in the Territory is infringing any right in the
Intellectual Property, it shall promptly notify the other Party in writing. Such
infringement may include, without limitation, any infringements or possible
infringements of any of Aviron's patents, registered designs and copyright and
of any use by any other person of a trade name, trade dress or get-up of goods
or mode of advertising which might amount to infringement of Aviron's rights or
passing-off. The Steering Committee shall then determine an appropriate strategy
for dealing with such infringement. The Steering Committee shall not have any
authority to abridge any legal right, 

---------

[ * ] = Confidential treatment requested.


                                      18.
<PAGE>   19
 including, but not limited to, any patent rights and trade secret enforcement
rights, held by Aviron outside the Territory; Aviron, in its sole discretion,
may elect to enforce any such legal right outside the Territory without the
necessity of obtaining advice from or consulting with the Steering Committee. 
[ * ] shall have the initial right to institute legal proceedings against such
Third Party. [ * ] shall render all reasonable assistance to [ * ] in the
prosecution of such proceedings as and when requested by [ * ]. Should [ * ]
elect not to institute proceedings against such other person, [ * ] be entitled
to institute proceedings whether in its own name or in the name of [ * ] without
the prior written consent of [ * ]. The costs of any suits brought under this
Section 12.2 will be [ * ] and any damages recovered therefrom will be [ * ].

         12.3 INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY. In the event
that a Party is notified by a Third Party that its exercise of its rights and
obligations hereunder may infringe such Third Party's intellectual property
rights, such Party shall promptly notify the other Party. The Steering Committee
shall determine an appropriate strategy for dealing with such alleged
infringement, and the costs related thereto will be [ * ].

         12.4 CSL COVENANTS. Save as hereinbefore provided, CSL covenants:

                  (a) Not to assign, apply for a patent on, register or
otherwise appropriate any Aviron Intellectual Property;

                  (b) To assign or transfer to Aviron and at Aviron's expense
any intellectual property rights which it might acquire covering or relating to
the Aviron Product, including any Joint Intellectual Property, or CSL
Intellectual Property, at the expiry or earlier termination of the Agreement.

                  (c) To assign to Aviron any Regulatory Approvals or
submissions therefor, or any pricing or reimbursement approvals obtained with
respect to the Aviron Product in the Territory, at the expiry or earlier
termination of the Agreement.

13.      CONFIDENTIALITY

         13.1 CONFIDENTIALITY OBLIGATIONS. Each Party shall keep secret and
confidential all Confidential Information of the other (as defined in Section
13.2 below) disclosed to it for the purposes of this Agreement. Each Party shall
also use its [ * ] to prevent the disclosure to any person, other than its
employees and authorized agents (and then only when such disclosure is required
for the proper performance of this Agreement), of all Confidential Information
of the other. Each Party shall use its [ * ] to ensure that the Confidential
Information of the other is not used except as expressly allowed by this
Agreement. Each Party shall be responsible for ensuring that its employees and
authorized agents do not disclose Confidential Information of the other to a
Third Party or make any unauthorized use of the Confidential Information. Each
Party shall be responsible for maintaining the Confidential Information with the
same degree of care which it uses to maintain its own confidential information
and which it warrants as providing adequate protection of such information from
unauthorized disclosure, copying or use.

------------------

[ * ] = Confidential treatment requested.


                                      19.
<PAGE>   20

         13.2 DEFINITION OF CONFIDENTIAL INFORMATION. In this Agreement,
"Confidential Information" means any confidential or proprietary information,
whether disclosed in writing, verbally or by any other means, and whether
disclosed before or after the date of this Agreement, concerning the business of
a Party, information related to a Collaboration Product and information related
to any Party's operations, processes, plans or intentions, production
information, information contained in the Aviron Intellectual Property and CSL
Intellectual Property, Know-How, data, formulae, expertise, methodology,
drawings, specifications, design rights, trade secrets, inventions, market
opportunities and business affairs, production methods, results of animal
testing of the Aviron Product or Aviron Product Materials, any market research
and any new and novel combinations thereof, but does not include information
which:

                  (a) is in or comes into the public domain without any breach
of this Agreement by the receiving Party; or

                  (b) the receiving Party can show by competent written evidence
(i) was in its possession or known to it by being recorded in its files prior to
disclosure by the disclosing Party; or (ii) to have been independently developed
by it in the course of work by its employees who have not had access to the
Confidential Information; or

                  (c) the receiving Party obtains or has available from a source
other than the disclosing Party without breach by the receiving Party or such
source of any obligation of confidentiality or non-use; or

                  (d) is disclosed by the receiving Party with the prior written
approval of the disclosing Party.

         13.3 PERMISSIBLE DISCLOSURE. Each Party may divulge Confidential
Information in confidence to any governmental authority to the extent required
to obtain Regulatory Approval and/or PBS Listing of the Aviron Product, provided
that such Party gives the other Party reasonable advance written notice of such
disclosure.

         13.4 RETURN OF CONFIDENTIAL INFORMATION. Upon termination or expiry as
the case may be of this Agreement, the receiving Party shall return to the
disclosing Party promptly all documents and materials and copies thereof
containing the Confidential Information of the disclosing Party, except that it
may retain one archival copy thereof for the sole purpose of being able to
determine the scope of its continuing obligations hereunder.

         13.5 PUBLICITY. The Parties agree that the public announcement of the
execution of this Agreement shall be as mutually agreed upon by the Parties. Any
other publication, news release or other public announcement relating to this
Agreement or to the performance hereunder, shall first be reviewed and approved
by both Parties, which approval shall not be unreasonably withheld; provided,
however, that any disclosure which is required by law as advised by the
disclosing Party's counsel may be made without the prior consent of the other
Party, although the other Party shall be given prompt notice of any such legally
required disclosure and to the extent practicable shall provide the other Party
an opportunity to comment on the proposed disclosure. The Parties acknowledge
that Aviron will be obligated to file a copy of this Agreement with the U.S.
Securities and Exchange Commission. Aviron will submit a 


                                      20.
<PAGE>   21
copy of its proposed filing to CSL for approval, which approval shall not be
unreasonably withheld.

         13.6 DISCLOSURE OF JOINT INTELLECTUAL PROPERTY. Each Party agrees that
it shall maintain in confidence and not disclose to Third Parties, any Joint
Intellectual Property, except as is consistent with the license grants set forth
in Section 7.1, 7.3 and 18.3 (g), without the written consent of the other
Party.

14.      REPRESENTATIONS AND WARRANTIES

         14.1 AVIRON REPRESENTATIONS AND WARRANTIES.

                  (a) Aviron warrants and represents that as of the Effective
Date it is not aware that the manufacture, use or sale in the Territory of the
Aviron Product will infringe any Third Party intellectual property;

                  (b) Aviron represents and warrants that it [ * ].

         14.2 CSL REPRESENTATIONS AND WARRANTIES. CSL warrants and represents
that [ * ].

         14.3 MUTUAL REPRESENTATIONS AND WARRANTIES. Each Party warrants and
represents that it has full power and authority to enter into this Agreement and
to meet the obligations hereunder.

15.      PRODUCT RECALL

         15.1 NOTIFICATION.

                  (a) BY CSL.

                           (i) CSL shall immediately inform Aviron forthwith by
telephone (immediately confirmed in writing) or by facsimile transmission in the
event of any circumstances giving rise to a possible or actual recall of the
Aviron Product in the Territory. Any recall actually undertaken shall be subject
to the approval of the Steering Committee.

                           (ii) Where such product recall has been initiated,
whether by the relevant registration authority or other authority or by the
Parties, CSL shall inform all purchasers of the Aviron Product so affected and
shall require them to deliver or to make available for collection all such
stocks of the Aviron Product in their possession.

                  (b) BY AVIRON. Aviron shall notify CSL immediately if a
product recall of the Aviron Product has been initiated by Aviron or any
licensee or distributor of Aviron in any country of the world other than in the
Territory.

         15.2 COSTS. The costs associated with a recall of Aviron Product in the
Territory shall be [ * ] provided that where such costs are [ * ].


------------------

[ * ] = Confidential treatment requested.

                                      21.
<PAGE>   22

16.      ADVERSE DRUG REPORTS

         16.1 NOTIFICATION.

                  (a) If CSL receives any report of an adverse drug experience
alleged to be caused by the Aviron Product, CSL shall report the matter to the
relevant regulatory authorities in compliance with the laws and regulations of
the Territory and inform Aviron immediately forthwith by telephone or facsimile
transmission (immediately confirmed in writing). In addition, if Aviron receives
any report of an adverse drug experience alleged to be caused by the Aviron
Product in any country of the world other than the Territory, Aviron shall
immediately advise CSL accordingly.

                  (b) CSL shall report to Aviron by telephone or facsimile
transmission (immediately confirmed in writing) of any serious, unexpected
adverse drug experience occurring in the Territory and alleged to be caused by
the Aviron Product within two days of the date upon which CSL first received
details of it. For the purposes of this sub-clause "serious" and "unexpected"
shall have the meaning prescribed to them at the relevant time by the relevant
regulatory authorities in the Territory.

         16.2 QUARTERLY REPORTS. All adverse drug experiences occurring in the
Territory and with respect to which CSL has reporting requirements under Section
16.1 above will be reported to Aviron in writing on a quarterly basis and the
report shall clearly indicate which cases have previously been reported to
Aviron under the terms of 16.1 above.

         16.3 ALLEGED DEFECTS.

                  (a) Each Party shall give immediate written notice to the
other of any alleged manufacturing or other defect in the Aviron Product of
which such Party becomes aware, and of any possible expense, liability, cost,
claim or proceedings arising from the alleged defect.

                  (b) With respect to any adverse drug experiences alleged to be
caused by, and any alleged manufacturing or other defect in, the Aviron Product,
neither Party shall make any admission of liability or other disclosure that is
not required by law to any Third Party with respect to claims, either in the
name of or on behalf of the other Party without the other Party's prior written
consent.

17.      INDEMNIFICATION

         17.1 COVENANT TO INDEMNIFY. Each Party hereby agrees to save, defend
and hold the other Party and its agents and employees harmless from and against
any and all suits, claims, actions, demands, liabilities, expenses and/or loss,
including reasonable legal expense and attorneys' fees ("Losses") resulting
directly or indirectly from the [ * ] by the indemnifying Party, its Affiliates,
agents or sublicensees in the Territory during the term of this Agreement, but
only to the extent such Losses [ * ]. Any other Losses resulting directly or
indirectly from the [ * ] shall be included as [ * ]

------------------

[*] = Confidential treatment requested.


                                      22.
<PAGE>   23

[ *] of the Party incurring such Losses at the time such claim is finally
determined, whether by judgment, award, decree or settlement.

         17.2 INDEMNIFICATION PROCEDURE. In respect to the indemnities provided
in this Article 17 hereof, the indemnified Party shall promptly notify the
indemnifying Party in writing of any claims, proceedings, or other actions or
the threat thereof in respect of which indemnification may be sought. The
indemnified Party shall reasonably cooperate with the indemnifying Party in
connection with defending or settling any claim, proceeding or other action in
respect of which indemnification may be sought. No settlement of any claim,
proceeding or other action or threat thereof for which indemnification is sought
shall be made without the prior written approval of the indemnifying Party,
which will not be unreasonably withheld. The indemnifying Party will have the
sole control over the defense and/or settlement of any claim, proceeding, or
other action for which indemnification is sought, subject to the indemnified
Party's right to select and use its own counsel at the indemnified Party's sole
cost and expense.

18.      TERMINATION

         18.1 TERM OF AGREEMENT.

                  (a) INITIAL TERM. This Agreement shall expire upon the later
of (a) six (6) years from the Effective Date, or (b) six (6) years from Market
Launch (the "Initial Term").

                  (b) RENEWAL. In the event either of the following events
(each, a "Triggering Event") has occurred:

                           (i) CSL has sold in the Territory at least [ * ] of
                   the Aviron Product in [ * ] years from Market Launch; or

                           (ii) CSL has obtained [ * ] for the Aviron Product in
                  Australia for [ * ] any time prior to such expiration date,

                  then CSL shall have the right, upon thirty (30) days written
notice to Aviron (but in no event after the termination or expiration of the
Initial Term, except with Aviron's prior written consent), to renew the term of
this Agreement for an additional six (6) years, subject to Aviron's right to
terminate during such additional term, as provided in Section 18.2(d). It is
understood by the Parties that such renewal shall be on the same terms and
conditions as herein contained. In the event that neither Triggering Event has
occurred prior to expiration of the Initial Term, this Agreement shall
terminate, unless otherwise agreed upon by the Parties.

         18.2 TERMINATION. This Agreement may be terminated:

                  (a) By the Party not affected by giving to the other Party
written notice to terminate on the date specified in the notice should any of
the following events occur, namely:


------------------

[*] = Confidential treatment requested.


                                      23.
<PAGE>   24

                           (i) Either Party becoming bankrupt or having a 
receiver appointed of its assets, or execution or distress levied upon its
assets;

                           (ii) An order being made or a resolution being passed
for winding-up or liquidation of either Party;

                           (iii) Failure of either Party to observe any of the
terms hereof to a material and significant extent and to remedy the same within
the period specified in a notice given by the aggrieved Party to the Party in
default calling for remedy, such period being not less than [ * ] days;

                           (iv) Being for any cause beyond its reasonable
control prevented from performing its duties hereunder for a continuous period
of [ * ] months or for a total period of [ * ] months in any period of [ * ]
calendar months; or

                           (v) Effective control of the other Party changes, 
except pursuant to the merger or sale of substantially all the assets of a
Party.

                  (b) By CSL on [ * ] days written notice to Aviron, provided
that such termination is due to the legitimate failure of the Aviron Product to
receive Regulatory Approval within a reasonable period from the Effective Date.

                  (c) In the event that the [ * ] is insufficient to meet CSL's
anticipated revenue requirements, CSL may terminate this Agreement, effective on
the later of (i) [ * ] days written notice to Aviron, or (ii) the [ * ] in the
Territory, provided such [ * ] is not later than [ * ] months from the date of
Aviron's receipt of notice from CSL under this Section 18.2(c).

                  (d) By Aviron in the event that, during any extended term of
this Agreement as provided under Section 18.1(b), [ * ]. This provision would
apply, for example, where the [ * ] following Market Launch was [ * ] following
Market Launch.

         18.3 EFFECT OF TERMINATION. On termination or expiration of this
Agreement:

                  (a) CSL will reasonably co-operate with Aviron and any
successor of CSL appointed by Aviron and (if applicable) any other distributor
of the Aviron Product in the Territory with a view to ensuring an orderly
transfer of any licenses and distribution responsibilities.

                  (b) CSL shall provide Aviron with full particulars of all
unsold Aviron Product (including quantities of each Aviron Product, and the
dates on which the Aviron Product was manufactured) in its possession. Aviron
shall be entitled at its discretion to purchase from CSL, at a price equal to [
* ], any unsold Aviron Product.

                  (c) If so requested by Aviron, CSL shall arrange for delivery
of the Aviron Product purchased by Aviron pursuant to Section 18.3(b) to such
destination or destinations as 


------------------

[*] = Confidential treatment requested.

                                      24.
<PAGE>   25

may be designated by Aviron. All delivery arrangements shall be subject to the
prior approval of Aviron. Freight and insurance of such delivery shall be [ * ].

                  (d) Any Aviron Product in respect of which Aviron has notified
CSL in writing that it does not wish to repurchase pursuant to Section 18.3(b)
may be sold by CSL within six (6) months after termination, in which case the
terms of this Agreement or such of them as is or are relevant shall continue to
operate until the remaining Aviron Product has been sold or the period of six
(6) months expires, whichever first occurs.

                  (e) CSL shall promptly forward to Aviron, at CSL's costs, all
Confidential Information and all promotional and advertising materials and all
technical information relating to the Aviron Product then in CSL's possession.
CSL shall not keep any copies of such materials and information, except as
provided in Section 13.4.

                  (f) CSL shall [ * ] for goodwill (e.g. the customer base)
which may have accrued to the marketing of the Aviron Product in the Territory,
and Aviron may [ * ] the Aviron Product as it may [ * ] the goodwill in such
marketing exercise.

                  (g) Aviron shall grant to CSL a [ * ] license, [ * ],
under [ * ].

         18.4 NO PREJUDICE. The termination of this Agreement shall be without
prejudice to the rights of the Parties accrued up to the date of such
termination or continuing thereafter.

19.      ANCILLARY PROVISIONS

         19.1 CONSTRUCTION OF AGREEMENT. In this Agreement, unless inconsistent
with the context or the subject matter:

                  (a) References to the singular shall include references to the
plural and vice versa;

                  (b) References to Articles, Sections and Schedules are
references to Articles, Sections and Schedules of this Agreement;

                  (c) References to persons shall include references to bodies
corporate and vice versa;

                  (d) Words denoting any gender shall include all genders; and

                  (e) Article and Section headings shall be disregarded.

         19.2 ASSIGNMENT. Neither Party shall have the right to assign this
Agreement or the rights or obligations hereunder to a Third Party without the
prior written consent of the other

------------------

[*] = Confidential treatment requested.


                                      25.
<PAGE>   26

Party, except pursuant to a merger, acquisition or sale of substantially all of
the assigning Party's assets.

         19.3 SUB-DISTRIBUTORS. CSL shall not be entitled to appoint any
sub-distributor except with the prior written consent of Aviron unless the
distributor is a wholly-owned subsidiary of CSL or an entity with which CSL has
a distribution agreement in place as at the date of this Agreement. All
sub-distributors appointed by CSL shall agree to comply with the terms of this
Agreement, and CSL shall use it best efforts to ensure such compliance.

         19.4 ENTIRE AGREEMENT. This Agreement together with the Option
Agreement embodies all the terms binding between the Parties hereto and replaces
all previous representations or proposals not embodied herein. Amendments hereto
shall not come into operation until duly embodied in any amending Agreement
properly executed on behalf of both Parties hereto.

         19.5 WAIVER. No waiver by either Party of any default in the strict and
literal performance of or any compliance with any provision, condition or
requirement contained in this Agreement shall be deemed to be a waiver of strict
and literal performance of and compliance with any other provision, condition or
requirement contained in this Agreement nor to be a waiver or in any manner a
release of the other Party from strict compliance with any provision, condition
or requirement in the future. Nor shall any delay or omission of any Party to
exercise any right under this Agreement in any manner impair the exercise of any
such right accruing to it thereafter. Unless otherwise expressly stated, no
remedy granted in this Agreement to either Party shall be deemed to exclude any
other remedy which would otherwise be available.

         19.6 COSTS. Each Party shall bear its own legal costs and expenses of
and incidental to the preparation of this Agreement.

         19.7 GOVERNING LAW. This Agreement shall be interpreted and governed by
the laws of the State of California as applied to agreements executed and
performed entirely within California by California residents.

         19.8 DISPUTES. The Parties will attempt to resolve all disputes under
this Agreement in a friendly and constructive manner. If the Parties are unable
to so resolve such dispute within [ * ] days, either Party may then seek to
settle such dispute [ * ].

         19.9 Survival.

                  (a) Sections 4.3(c), 7.3, 7.4, 9.3, 9.4, 11.2, 12.1 and 12.4
and Articles 10 (as applicable) 13, 15, 16, 17, 18, 19 and 20 of this Agreement
shall survive termination or expiry of this Agreement.

------------------

[*] = Confidential treatment requested.


                                      26.
<PAGE>   27

                  (b) CSL's obligations under Articles 6, 13, 14, 16, 20 and 22
and Sections 9.4, 15.5 and 15.6 of the Michigan Agreement shall survive
termination or expiration of this Agreement.

         19.10 FORCE MAJEURE. A Party shall not be liable for any failure to
perform or observe any term of this Agreement if performance or observance has
been delayed, hindered, restricted or prevented by any circumstance not within
the direct control of such Party including without limiting the generality of
the foregoing Acts of God, strikes, lock-outs or other industrial disturbances,
war, hostilities or the threat or apprehension thereof, or any interruption to
the supply of materials or information, or any accident or breakdown of
machinery or the making of emergency or essential repairs thereto, or compliance
with any valid order of any governmental or public authority. The time or times
for performances of the obligations on the respective Parties to be performed
herein shall be extended by a period equal to each such period of delay,
provided that such Party shall forthwith give notice to the other Party in
accordance with the provisions of this Agreement and shall endeavor to remove or
remedy the cause thereof with all due diligence and expedition, provided that,
either Party may terminate this Agreement pursuant to Section 18.2(a)(iv)
herein.

         19.11 INDEPENDENT CONTRACTORS. The relationship between the Parties is
solely that of independent contractors and is not intended to be a means through
which Aviron creates a permanent establishment in the Territory. Otherwise than
as permitted by this Agreement, CSL is not authorized to act on behalf of Aviron
purporting to bind Aviron, but shall act as an independent entity buying for
itself and selling in its own name and at its own risk subject only to Section
16.1. CSL undertakes not to pledge the credit of Aviron and shall have no power
or authority to do so.

         19.12 SIGNATURES. All Aviron signatures to this Agreement and all other
agreements between the Parties shall be executed by Aviron in the United States.

20.      NOTICES

         20.1 ADDRESSES AND FACSIMILES. Where this Agreement requires a written
notice, the notice may be given by post, personal delivery or facsimile
transmission, to the other Party and is to be marked to the attention of the
person from time to time designated for this purpose by the other Party. The
signatories to this Agreement are the persons initially designated for this
purpose and their respective initial addresses and facsimile numbers are set out
hereunder:

                  CSL LIMITED A.C.N. 051 588 348
                  45 Poplar Road, Parkville, Victoria Australia, 3052
                  Facsimile + 61 3 9389 1434

                  Aviron
                  297 North Bernardo Avenue
                  Mountain View, California 94043
                  U.S.A.
                  Facsimile +1 650 919 6612



                                      27.
<PAGE>   28

                  With a copy to:
                  Cooley Godward, LLP
                  3000 El Camino Real
                  5 Palo Alto Square
                  Palo Alto, CA  94306-2155
                  Attention: Barbara A. Kosacz, Esq.


         20.2 RECEIPT. No written notice is to be effective until received, or
deemed to be received by the other Party as follows:

                  (a) in the case of personal delivery, upon delivery;

                  (b) in the case of a letter, on the fifth business day after
posting (business days to be determined according to the place of receipt); and

                  (c) in the case of a facsimile transmission, on the business
day on which it is dispatched, or, if dispatched on a non-business day, or after
5 pm on a business day then on the next business day (times and business days to
be determined according to the place of receipt) after the day on which it is
dispatched. A record from the dispatching facsimile machine detailing the time
and date of the transmission shall be evidence of transmission, unless proved to
the contrary.




                                      28.
<PAGE>   29


         IN WITNESS WHEREOF the Parties hereto have executed this Agreement the
day and year first hereinbefore written.


Signed for and on behalf of                Signed for and on behalf of

CSL LIMITED A.C.N. 051 588 348             AVIRON

by its duly authorized representatives     by its duly authorized representative


--------------------------------------     -------------------------------------



Stan McLiesh                               J. Leighton Reid
General Manager Pharmaceuticals            Chief Executive Officer


--------------------------------------     -------------------------------------

Date                                       Date



--------------------------------------     

Peter Turvey
Company Secretary


--------------------------------------      

Date



                                      29.
<PAGE>   30

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY BRACKETS,
HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.


                                  SCHEDULE 1.20

                               MICHIGAN AGREEMENT



The Michigan Agreement was previously filed as Exhibit 10.3 to Form S-1 dated
June 5, 1996, and is hereby incorporated by reference.



                                       1.
<PAGE>   31

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY BRACKETS,
HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.


                                  SCHEDULE 4.1

                       OUTLINE OF THE INCREMENTAL STUDIES

       TASK                                   RESPONSIBILITY ASSIGNMENT
      ---------------------               ------------------------------------
              [*]



                                       1.

<PAGE>   32


                                  SCHEDULE 4.1

                       OUTLINE OF THE INCREMENTAL STUDIES

       TASK                                   RESPONSIBILITY ASSIGNMENT
      ---------------------               ------------------------------------
              [*]


                                       2.

<PAGE>   33

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY BRACKETS,
HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.

--------------------------------

                                  SCHEDULE 7.7

                                OPTION AGREEMENT


THIS AGREEMENT is made on                                     1998 between:


1.       CSL LIMITED (ACN 051 588 348) incorporated in the Australian Capital
         Territory of 45 Poplar Road, Parkville, Victoria, Australia (CSL); and

2.       AVIRON incorporated in Delaware, USA of 297 North Bernardo Avenue,
         Mountain View, California, USA (AVIRON).


RECITALS

A.       CSL has sufficient authorised and unissued share capital to enable it
         to issue the Option Securities.

B.       In consideration for Aviron entering into the Collaboration Agreement,
         CSL has agreed to grant to Aviron Options to subscribe for the Option
         Securities on the terms of this Agreement.


IT IS AGREED as follows.

1.       DEFINITIONS AND INTERPRETATION

1.1      DEFINITIONS

         In this Agreement, including the Recitals, the following definitions
         apply unless the context requires otherwise.

         ASX means the Australian Stock Exchange Ltd.

         ACCEPTANCE PERIOD means the period commencing on the date [ *** *** ]
         and ending at 4.00pm (Melbourne time) on the date five (5) years after
         the date of commencement of the Acceptance Period.

         APPLICATION PERIOD means the period commencing on the date [ *** *** ]
         and ending at 4.00pm (Melbourne time) on the date five (5) years after
         the date of commencement of the Application Period.

----------------------

[***] = Confidential treatment requested.

<PAGE>   34
                                     Page 2


         AVIRON PRODUCT has the same meaning as that term is defined in the
         Collaboration Agreement.

         BUSINESS DAY means a week day on which banks are open in Melbourne.

         BUY-OUT NOTICE means a notice substantially in the form set out in
         Annexure B.

         COLLABORATION AGREEMENT means the Influenza Vaccine Collaboration
         Agreement between CSL and Aviron concerning the development, marketing
         and sale of the Aviron Product entered into concurrently with this
         Agreement.

         COMPLETION means in respect to any of the Options completion of the
         exercise of those Options in accordance with Clause 4.

         ENCUMBRANCE means mortgage, charge, lien, security interest or other
         encumbrance of any kind and however arising.


<PAGE>   35
                                     Page 3


         EXPERT, as referred to in Clause 12, means an independent chartered
         accountant:

         (a)      agreed by the parties; or

         (b)      failing agreement within 30 days of either party nominating to
                  the other a particular person, nominated at the request of
                  either party by the President of the Institute of Chartered
                  Accountants in Australia.

         FIRB BUY-OUT NOTICE means a notice substantially in the form set out in
         Annexure D.

         OPTION EXERCISE PRICE means (subject to Clause 6) in respect of each
         Option Security, the lower of:

         (a)      the weighted average sale price of fully paid CSL ordinary
                  shares quoted on the ASX for the five trading days preceding
                  the date of this Agreement; and

         (b)      the weighted average sale price of fully paid CSL ordinary
                  shares quoted on the ASX for the thirty trading days
                  preceding:

                  (i)      in respect of an Option Security issued pursuant to
                           the exercise of the Option referred to in Clause
                           2.1(a), the date of the commencement of the
                           Application Period; or

                  (ii)     in respect of an Option Security issued pursuant to
                           the exercise of the Option referred to in Clause
                           2.1(b), the date of the commencement of the
                           Acceptance Period; or

                  (iii)    in respect of an Option Security issued pursuant to
                           the exercise of the Option referred to in Clause
                           2.1(c), the date of the commencement of the Third
                           Period;

         plus the following premium per share:

         (A)      if the Option Security is issued pursuant to the exercise of
                  the Option referred to in Clause 2.1(a), $1.00;

         (B)      if the Option Security is issued pursuant to the exercise of
                  the Option referred to in Clause 2.1(b), $1.50; and

         (C)      if the Option Security is issued pursuant to the exercise of
                  the Option referred to in Clause 2.1(c), $2.00.

         OPTION NOTICE means a notice given to CSL under Clause 3.1.

         OPTION PERIOD RESTRICTION means a law or regulation applicable to CSL
         (including a provision of the Corporations Law or the listing rules of
         the ASX) which imposes a limit on the exercise period of an option
         granted by CSL to take up unissued shares in CSL of less than ten (10)
         years after the date the option was granted.


<PAGE>   36
                                     Page 4


         OPTION SECURITIES means (subject to Clause 6) one million (1,000,000)
         ordinary shares of $1.00 each in the capital of CSL.

         OPTIONS means the Options referred to in Clause 2.

         PREVAILING CSL SHARE PRICE means, for the purposes of Clauses 7 and 10,
         the weighted average price of CSL ordinary shares sold on the ASX
         during the [***] trading days immediately preceding the date on which
         the relevant Buy-Out Notice or FIRB Buy-Out Notice (as the case may be)
         is received by CSL.

----------------------

[***] = Confidential treatment requested.


<PAGE>   37
                                     Page 5



         RELEVANT CONDITION PRECEDENT means:

         (a)      in the case of the Option referred to in Clause 2.1(a), 
                  [ * * *
                                     * * *
                   * * * ]

         (b)      in the case of the Option referred to in Clause 2.1(b), 
                  [ * * *

                                     * * *
                  * * * ]; and

         (c)      in the case of the Option referred to in Clause 2.1(c), the
                  occurrence of the event which causes the Third Period to
                  commence.

         REORGANISATION means in relation to CSL any consolidation, subdivision
         or reduction of capital, or any other form of reorganisation affecting
         CSL's share capital.

         TGA means the Australian Therapeutic Goods Administration.

         THIRD PERIOD means the period commencing on the first to occur of:

         (a)      the date CSL first [                * * *
                                                      * * *
                                                      * * ];  or

         (b)      the date that [                     * * *
                                                      * * *
                                                      * * *]

         and ending at 4.00pm (Melbourne time) on the date [ *** ] after the
         date of commencement of the Third Period.

1.2      INTERPRETATION

         Headings are for convenience only and do not affect interpretation. The
         following rules apply unless the context requires otherwise.

         (a)      The singular includes the plural and conversely.

         (b)      A gender includes all genders.

         (c)      If a word or phrase is defined, its other grammatical forms
                  have a corresponding meaning.

         (d)      A reference to a person, corporation, trust, partnership,
                  unincorporated body or other entity includes any of them.

----------------------

[***] = Confidential treatment requested.

<PAGE>   38
                                     Page 6


         (e)      A reference to a Clause or Annexure is a reference to a Clause
                  of, or annexure to this Agreement.

         (f)      A reference to an agreement or document (including, without
                  limitation, a reference to this Agreement) is to the agreement
                  or document as amended, varied, supplemented, novated or
                  replaced, except to the extent prohibited by this Agreement or
                  that other agreement or document.

         (g)      A reference to a party to this Agreement or another agreement
                  or document includes the party's successors and permitted
                  substitutes or assigns (and, where applicable, the party's
                  legal personal representatives).


<PAGE>   39
                                     Page 7


         (h)      A reference to legislation or to a provision of legislation
                  includes a modification or re-enactment of it, a legislative
                  provision substituted for it and a regulation or statutory
                  instrument issued under it.

         (i)      A reference to conduct includes, without limitation, an
                  omission, statement and undertaking, whether or not in
                  writing.

         (j)      A reference to DOLLARS and $ is to Australian currency.

         (k)      Any terms used in the Collaboration Agreement which are not
                  assigned a different meaning in this Agreement have the same
                  meaning when used in this Agreement.

2.       AGREEMENT TO GRANT OPTIONS

2.1      AGREEMENT TO GRANT OPTIONS

         In consideration of Aviron entering into the Collaboration Agreement
         with CSL, CSL agrees to grant to Aviron each of the following Options
         subject to, and with effect on and from, the satisfaction of the
         Relevant Condition Precedent in each case:

         (a)      the option to subscribe for and be allotted [ * * * ] of the
                  Option Securities at any time during the Application Period;

         (b)      the further option to subscribe for and be allotted [ * * *]
                  of the Option Securities at any time during the Acceptance
                  Period; and

         (c)      the further option to subscribe for and be allotted [ * * * ]
                  of the Option Securities at any time during the Third Period;

         in accordance with this Agreement.

2.2      LIMITATION

         Notwithstanding any other provision of this Agreement, any unexercised
         Options or alternative options granted under Clause 2.5, and any rights
         under Clauses 7 and 10, shall lapse if for any reason (other than
         breach of contract by CSL) the Collaboration Agreement is terminated.

2.3      GRANT OF OPTIONS

         CSL must grant each Option within 21 days of the satisfaction of the
         Relevant Condition Precedent in each case by issuing a notice in the
         form of Annexure C to Aviron.

2.4      AVOIDANCE OF DOUBT

----------------------

[***] = Confidential treatment requested.


<PAGE>   40
                                     Page 8


         To avoid any doubt, the parties agree that each Relevant Condition
         Precedent operates as a condition which must be satisfied in each case
         before CSL may grant the relevant Option referred to in Clause 2.1 and
         each such Option will be separately granted and is not dependent upon
         the valid grant of any other such Option.


<PAGE>   41
                                     Page 9



2.5      GRANT OF ALTERNATIVE OPTIONS

         In further consideration of Aviron entering into the Collaboration
         Agreement with CSL, and subject to the second sentence of this Clause
         2.5, CSL hereby grants options in the same terms as those set out in
         paragraphs (a), (b) or (c) of Clause 2.1 except with the addition of
         the words [ * * *  * * *  * * * ] in each case. Each of the options
         granted under this Clause 2.5 is only exercisable in the event that the
         corresponding Option referred to in Clause 2.1 is void by reason of
         breaching any Option Period Restriction.

2.6      UNDERTAKING BY CSL

         CSL agrees that it will not initiate or support (financially or
         otherwise) any claim that any Option is void by reason of breach of any
         Option Period Restriction.

3.       EXERCISE OF THE OPTIONS

3.1      EXERCISE BY NOTICE

         Aviron may from time to time exercise any or all of the Options by
         notice to CSL.

3.2      CONTENTS OF NOTICE

         A notice given under Clause 3.1 must be in the form set out in Annexure
         A and must specify a Business Day on which Completion shall take place.
         Subject to Clause 3.3, that Business Day must be not less than [* * *]
         nor more than [* * *] after the date on which that notice is given.

3.3      REGULATORY REQUIREMENTS

         It is the responsibility of Aviron to comply with all regulatory
         requirements (including the filing of any notice required under the
         Foreign Acquisitions and Takeovers Act 1975) concerning the
         subscription for the Option Securities. If Aviron files a notice under
         the Foreign Acquisitions and Takeovers Act 1975 in relation to the
         exercise of some Options, Aviron may in the relevant Option Notice
         specify as the day on which Completion shall take place the seventh
         Business Day after Aviron has notified CSL that the Treasurer of
         Australia has confirmed the Australian Government has no objection to
         Aviron acquiring the relevant Option Securities.

4.       COMPLETION

4.1      PLACE OF COMPLETION


----------------------

[***] = Confidential treatment requested.

<PAGE>   42
                                    Page 10


         Completion of any subscription and issue of Option Securities under
         Clause 3.1 shall take place at the offices of CSL, 45 Poplar Road,
         Parkville, Victoria (or such other place as the parties may agree)
         before 5.00pm on the date specified in the notice exercising the Option
         given under Clause 3.1.

4.2      PAYMENT OF THE OPTION PRICE

         On Completion Aviron shall pay to CSL, as CSL may direct, the Option
         Exercise Price in respect of the number of Option Securities specified
         in the Option Notice. Payment shall be made by telegraphic transfer of
         cleared funds in Australian currency to a bank account nominated by
         CSL, or by bank draft in Australian dollars and drawn on, and payable
         at, an Australian bank.


<PAGE>   43
                                    Page 11



4.3        ISSUE OF SHARES

           On Completion, CSL shall allot and issue one fully paid ordinary
           share in CSL ranking pari passu with the then issued ordinary shares
           for the number of Option Securities specified in the Option Notice.

4.4        ACTIONS AFTER COMPLETION

           Promptly after Completion CSL will apply for the new shares issued
           pursuant to the exercise of the Options to be listed on the ASX and
           will arrange for the CSL share registrar to issue a holding statement
           to Aviron confirming that Aviron is the registered holder of the
           Option Securities issued under Clause 4.3.

5.         WARRANTY, UNDERTAKING AND COVENANTS BY CSL

5.1        UNISSUED AUTHORISED SHARE CAPITAL

           CSL warrants to Aviron that CSL has sufficient authorised and
           unissued share capital to enable it to issue the Option Securities,
           and that the Option Securities will be issued as fully paid and free
           from any pre-emptive rights of any shareholder.

5.2        UNDERTAKING BY CSL

           CSL undertakes with Aviron that CSL will at all times until the
           expiry of the Third Period keep set aside out of its authorised
           capital such number of ordinary shares as would be necessary to
           satisfy the right conferred upon Aviron by this Agreement to exercise
           all the Options.

5.3        COVENANTS

           CSL covenants that:

           (a)         CSL will apply for listing of the Option Securities
                       promptly upon issue and will use its best endeavours to
                       obtain listing of the Option Securities as quickly as
                       possible after issue; and

           (b)         in the event that there is a pro rata issue or a bonus
                       issue of ordinary shares in CSL then the exercise price
                       of the Options or the number of securities over which the
                       Options are exercisable shall be adjusted in accordance
                       with the ASX Listing Rules.

6.         EFFECT OF REORGANISATION

           If in respect of any Option a Reorganisation occurs between the date
           of this Agreement and Completion the Option Exercise Price, and the
           Option Securities to be issued upon exercise of the Option, shall be
           adjusted between the parties to take account of the Reorganisation in
           accordance with the Listing Rules of the ASX.


<PAGE>   44
                                    Page 12


7.         BUY-OUT RIGHTS

7.1        APPLICATION PERIOD OPTION

           If:

           (a)        the Option referred to in Clause 2.1(a) is void by reason
                      of breaching an Option Period Restriction;


<PAGE>   45
                                    Page 13


           (b)         the Relevant Condition Precedent has occurred;

           (c)         the period during which the corresponding alternative
                       option granted under Clause 2.5 must be exercised expires
                       [* * *] after the date of this Agreement; and

           (d)         that corresponding alternative option has not been
                       exercised during that [* * *] period,

           Aviron will have the right from the expiry of that five year period
           until 4.00pm (Melbourne time) on the date the Application Period
           expires to serve a Buy-Out Notice on CSL which relates to that
           Option. Within [* * *  * * *] days after receiving such Buy-Out
           Notice, CSL must pay to Aviron a cash amount calculated in accordance
           with the following formula:

                                        [* * *

                                        * * *

                                        * * *

                                        * * *
                                        * * *
                                        * * *

                                        * * *
                                        * * *
                                        * * *]

7.2        ACCEPTANCE PERIOD OPTION

           If:

           (a)        the Option referred to in Clause 2.1(b) is void by reason
                      of breaching an Option Period Restriction;

           (b)        the Relevant Condition Precedent has occurred;

           (c)        the period during which the corresponding alternative
                      option granted under Clause 2.5 must be exercised expires
                      [* * *] after the date of this Agreement; and

           (d)        that corresponding alternative option has not been
                      exercised during that [* * *] period,

----------------------

[***] = Confidential treatment requested.


<PAGE>   46
                                    Page 14


           Aviron will have the right from the expiry of that [* * *] period
           until 4.00pm (Melbourne time) on the date the Acceptance Period
           expires to serve a Buy-Out Notice on CSL which relates to that
           Option. Within [* * *  * * *] days after receiving such Buy-Out
           Notice, CSL must pay to Aviron a cash amount calculated in accordance
           with the following formula:

                                       [* * *

                                       * * *
                                       * * *


---------------

[* * *] = Confidential treatment requested.
<PAGE>   47
                                    Page 15



                                       * * *
                                       * * *
                                       * * *


                                       * * *
                                       * * *
                                       * * *]

7.3        THIRD PERIOD OPTION

           If:

           (a)        the Option referred to in Clause 2.1(c) is void by reason
                      of breaching an Option Period Restriction;

           (b)        the Relevant Condition Precedent has occurred;

           (c)        the period during which the corresponding alternative
                      option granted under Clause 2.5 must be exercised expires
                      [* * *] after the date of this Agreement; and

           (d)        that corresponding alternative option has not been
                      exercised during that [* * *] period,

           Aviron will have the right from the expiry of that five year period
           until 4.00pm (Melbourne time) on the date the Third Period expires to
           serve a Buy-Out Notice on CSL which relates to that Option. Within 
           [* * *] days after receiving such Buy-Out Notice, CSL must pay to 
           Aviron a cash amount calculated in accordance with the following 
           formula:

                                       [* * *

                                       * * *

                                       * * *

                                       * * *
                                       * * *
                                       * * *

                                       * * *
                                       * * *
                                       * * *]


----------------------

[***] = Confidential treatment requested.

<PAGE>   48
                                    Page 16


7.4        METHOD OF PAYMENT

           Any payment to be made by CSL pursuant to this Clause 7 must be made
           by telegraphic transfer of cleared funds in Australian currency to a
           bank account nominated by Aviron, or by bank draft in Australian
           dollars and drawn on, and payable at, an Australian bank, or by such
           other means as the parties agree.



<PAGE>   49
                                    Page 17




7.5        EFFECT OF COURT DECLARATION

           If any Option is exercised and subsequently declared by a court of
           competent jurisdiction to be void, Aviron will be deemed to have
           given a Buy-out Notice in respect of the right which corresponds to
           that Option under Clause 7, on the date notice was given purporting
           to exercise that Option, except that for the purposes of the
           obligation to make payment by CSL, such payment must be made within
           [* * *] after the date CSL receives notice from Aviron of the court's
           declaration.

8.         ACKNOWLEDGEMENT

           The parties acknowledge that CSL may be obligated to disclose the
           terms of this Agreement or file a copy of this Agreement with the
           ASX. CSL will submit a copy of any proposed disclosure to Aviron for
           approval (which approval will not be unreasonably withheld).

9.         WITHHOLDING TAX

9.1        OBLIGATION TO PAY

           If any withholding tax is payable in Australia in respect of the
           issue of any Option (or alternative option granted under Clause 2.5)
           (A TAX), [ * * * ] to the relevant Australian government authority
           (THE ATO) and [ * * * ] according to the terms of this Clause 9.

9.2        ADDITIONAL GROSS-UP PAYMENT

           If a payment in accordance with Clause 9.1 (or in accordance with a
           previous application of this Clause 9.2) is itself liable to
           withholding tax, [ * * *  * * *  * * * ] This Clause applies
           successively to each further increment to withholding tax calculated
           in accordance with this Clause 9.2. For the avoidance of doubt, any
           additional tax paid according to this Clause 9.2 will be treated as
           the payment of a Tax for the purposes of [* * *] pursuant to Clauses
           9.3 and 9.4.

9.3        [     * * *     ]

           After the commencement of the Acceptance Period, [ * * *  * * *  
           * * *] CSL will provide Aviron with written notice of [ * * * 
           * * *] CSL will provide Aviron with details of [ * * *  * * * ]

9.4        IF THE ACCEPTANCE PERIOD DOES NOT COMMENCE WITHIN [* * *]


----------------------

[***] = Confidential treatment requested.

<PAGE>   50
                                    Page 18


           If the Acceptance Period does not commence within [ * * *] after the
           date of commencement of the Application Period, [***] will
           immediately pay to [ * * *] an amount equal to [ * * *] of the net
           cost of any Tax [ * * *] in respect of the issue of the Option
           referred to in Clause 2.1(a). Upon commencement of the Acceptance
           Period, Clause 9.3 will apply, and the total amount [ * * * ]
           pursuant to Clause 9.3 will be reduced by the amount of [ * * * ]
           pursuant to this Clause 9.4.

----------------------

[***] = Confidential treatment requested.
<PAGE>   51
                                    Page 19



9.5        MEANING OF NET COST

           For the purpose of this Clause 9, "net cost" means the cost to
           [ * * * ] pursuant to Clauses 9.1 and 9.2, including the [ * * * ]
           and after taking into account any [ * * *  * * *]

10.        FIRB BUY-OUT RIGHTS

10.1       APPLICATION PERIOD OPTION

           If:

           (a)         the Relevant Condition Precedent has occurred;

           (b)         CSL has granted the Option referred to in Clause 2.1(a)
                       (or the corresponding alternative option granted under
                       Clause 2.5);

           (c)         Aviron files a notice under the Foreign Acquisition and
                       Takeovers Act 1975 (THE ACT) in relation to the exercise
                       of the Option referred to in Clause 2.1(a) (or the
                       corresponding alternative option referred to in Clause
                       2.5) to acquire CSL ordinary shares and the Treasurer of
                       Australia makes an order in accordance with the Act
                       objecting to Aviron's acquisition of CSL ordinary shares
                       pursuant to the exercise of that Option (or the
                       corresponding alternative option referred to in Clause
                       2.5) or makes an order with conditions [ * * *
                                     * * *         ]

           Aviron will have the right from the date that it receives such an
           order from the Treasurer of Australia until 4.00pm (Melbourne time)
           on the date the Application Period expires to serve a FIRB Buy-Out
           Notice on CSL which relates to that Option. Within thirty (30) days
           after receiving such FIRB Buy-Out Notice, CSL must pay to Aviron a
           cash amount calculated in accordance with the following formula:

                                  [* * *

                                   * * *

                                   * * *

                                   * * *
                                   * * *
                                   * * *

                                   * * *
                                   * * *
                                   * * *]

----------------------

[***] = Confidential treatment requested.

<PAGE>   52
                                    Page 20


10.2       ACCEPTANCE PERIOD OPTION

           If:

           (a)         the Relevant Condition Precedent has occurred;

           (b)         CSL has granted the Option referred to in Clause 2.1(b)
                       (or the corresponding alternative option granted under
                       Clause 2.5);


<PAGE>   53
                                    Page 21



           (c)         Aviron files a notice under the Act in relation to the
                       exercise of the Option referred to in Clause 2.1(b) (or
                       the corresponding alternative option referred to in
                       Clause 2.5) to acquire CSL ordinary shares and the
                       Treasurer of Australia makes an order in accordance with
                       the Act objecting to Aviron's acquisition of CSL ordinary
                       shares pursuant to the exercise of that Option (or
                       corresponding alternative option referred to in Clause
                       2.5) or makes an order with conditions [ * * * ]

           Aviron will have the right from the date that it receives such an
           order from the Treasurer of Australia until 4.00pm (Melbourne time)
           on the date the Acceptance Period expires to serve a FIRB Buy-Out
           Notice on CSL which relates to that Option. Within thirty (30) days
           after receiving such FIRB Buy-Out Notice, CSL must pay to Aviron a
           cash amount calculated in accordance with the following formula:

                                      [ * * *

                                       * * *

                                       * * *

                                       * * *
                                       * * *
                                       * * *

                                       * * *
                                       * * *
                                       * * *]

10.3       THIRD PERIOD OPTION

           If:

           (a)         the Relevant Condition Precedent has occurred;

           (b)         CSL has granted the Option referred to in Clause 2.1(c)
                       (or the corresponding alternative option granted under
                       Clause 2.5);

           (c)         Aviron files a notice under the Act in relation to the
                       exercise of the Option referred to in Clause 2.1(c) (or
                       the corresponding alternative option referred to in
                       Clause 2.5) to acquire CSL ordinary shares and the
                       Treasurer of Australia makes an order in accordance with
                       the Act objecting to Aviron's acquisition of CSL ordinary
                       shares pursuant to the exercise of that Option (or
                       corresponding alternative option referred to in Clause
                       2.5) or makes an order with conditions [ * * * ]


----------------------

[***] = Confidential treatment requested.
<PAGE>   54
                                    Page 22


           Aviron will have the right from the date that it receives such an
           order from the Treasurer of Australia until 4.00pm (Melbourne time)
           on the date the Third Period expires to serve a FIRB Buy-Out Notice
           on CSL which relates to that Option. Within thirty (30) days after
           receiving such FIRB Buy-Out Notice, CSL must pay to Aviron a cash
           amount calculated in accordance with the following formula:

                                     [ * ]

------------------

[*]  Certain information in this document has been omitted and filed separately 
     with the Commission. Confidential treatment has been requested with 
     respect to the omitted portions, which are marked by an "*" in the text.

<PAGE>   55
                                    Page 23



                                     * * *

                                     * * *
                                     * * *
                                     * * *

                                     * * *
                                     * * *
                                     * * *]

10.4       METHOD OF PAYMENT

           Any payment to be made by CSL pursuant to this Clause 10 must be made
           by telegraphic transfer of cleared funds in Australian currency to a
           bank account nominated by Aviron, or by bank draft in Australian
           dollars and drawn on, and payable at, an Australian bank, or by such
           other means as the parties agree.

11.        FURTHER ASSURANCES

           Each party agrees to do all things and execute all deeds,
           instruments, transfers or other documents as may be necessary or
           desirable to give full effect to the provisions of this Agreement and
           the transactions contemplated by it.

12.        RESOLUTION OF DISPUTES

12.1       REFERENCE TO EXPERT

           If a dispute between the parties has not been resolved within
           [ * * * ] Business Days of it arising, it shall be referred
           to an Expert for resolution.

12.2       EXPERT'S INSTRUCTIONS

           The Expert shall be instructed to:

           (a)        decide the dispute within the shortest practicable time;
                      and

           (b)        deliver a report containing his or her opinion with
                      respect to the matters in dispute and clearly stating the
                      reasons for the decision.

12.3       PROCEDURE

           The Expert shall determine the procedure for dispute resolution. The
           parties shall provide all information and assistance reasonably
           requested by the Expert for the purpose of resolving the dispute.


----------------------

[***] = Confidential treatment requested.

<PAGE>   56
                                    Page 24


12.4       CONCLUSIVENESS OF REPORT

           The Expert shall act in the capacity of independent expert, not as an
           arbitrator. The Expert's decision shall be [ * * * ]

12.5       COSTS

           [                          * * *
                                      * * *       ]
----------------------

[***] = Confidential treatment requested.
<PAGE>   57
                                    Page 25




13.        ENTIRE AGREEMENT

           This Agreement, together with the Collaboration Agreement, contains
           the entire agreement between the parties as at the date of this
           Agreement with respect to its subject matter and supersedes all prior
           agreements and understandings between the parties in connection with
           it.


14.        NOTICES

           Any notice, demand, consent or other communication (a NOTICE) given
           or made under this Agreement:

           (a)        must be in writing and signed by a person duly authorised
                      by the sender;

           (b)        must either be delivered to the intended recipient by
                      prepaid post (if posted to an address in another country,
                      by registered airmail) or by hand or fax to the address or
                      fax number below or the address or fax number last
                      notified by the intended recipient to the sender:


<TABLE>
<S>                                           <C>            
                      (i)    to CSL LIMITED:  45 Poplar Road,
                                              Parkville,
                                              Victoria  3052  Australia
                                              Attention:       Managing Director
                                              Fax No:          +613 9387 1685

                      (ii)   to AVIRON:       297 North Bernardo Avenue
                                              Mountain View
                                              California  94043  USA
                                              Attention:       Chief Executive Officer
                                              Fax No:          +1 650 919 6612

</TABLE>

           (c)        will be taken to be duly given or made:

                      (i)        in the case of delivery in person, when
                                 delivered;

                      (ii)       in the case of delivery by post two Business
                                 Days after the date of posting (if posted to an
                                 address in the same country) or seven Business
                                 Days after the date of posting (if posted to an
                                 address in another country); and

                      (iii)      in the case of fax, on receipt by the sender of
                                 a transmission control report from the
                                 despatching machine showing the relevant number
                                 of pages and the correct destination fax
                                 machine number or name of recipient and
                                 indicating that the transmission has been made
                                 without error,


<PAGE>   58
                                    Page 26


                       but if the result is that a Notice would be taken to be
                       given or made on a day that is not a business day in the
                       place to which the Notice is sent or is later than 4.00pm
                       (local time) it will be taken to have been duly given or
                       made at the commencement of business on the next business
                       day in that place.


15.        AMENDMENT

           No amendment or variation of this Agreement is valid or binding on a
           party unless made in writing executed by all parties.


<PAGE>   59
                                    Page 27



16.        ASSIGNMENT

           The rights and obligations of each party under this Agreement are
           personal. They cannot be assigned, encumbered or otherwise dealt with
           and no party shall attempt, or purport, to do so without the prior
           consent of all parties.


17.        COUNTERPARTS

           This Agreement may be executed in any number of counterparts. All
           counterparts will be taken to constitute one instrument.


18.        COSTS

           Each party shall bear its own costs arising out of the negotiation,
           preparation and execution of this Agreement.


19.        GOVERNING LAW AND JURISDICTION

           This Agreement is governed by the laws of Victoria. Each party
           submits to the non- exclusive jurisdiction of courts exercising
           jurisdiction there in connection with matters concerning this
           Agreement.



EXECUTED by the parties.


SIGNED  for and on behalf of CSL LIMITED  )
by its duly authorised representatives:   )


/s/  P. TURVEY                               /s/  B. McNAMEE
----------------------------------           -----------------------------------


----------------------------------           -----------------------------------
Print Name                                   Print Name


<PAGE>   60
                                    Page 28



SIGNED   for   and   on   behalf   of          )
AVIRON by its duly authorised representatives: )
                                               )

/s/  L. READ
----------------------------------           -----------------------------------


----------------------------------           -----------------------------------
Print Name                                   Print Name


<PAGE>   61
                                    Page 29


                                   ANNEXURE A

                                  OPTION NOTICE






To:        CSL Limited
           45 Poplar Road
           PARKVILLE   VIC   3052



TAKE NOTICE that AVIRON (AVIRON) exercises the number of Options specified below
in accordance with the Option Agreement made on [#] 1998 between CSL LIMITED
(CSL) and Aviron and requires CSL to issue and allot to Aviron the number of
Option Securities specified below in accordance with the Option Agreement.
Completion shall take place at [#] am/pm (Melbourne time) on [#] 199[#] at the
principal office of CSL Limited at [#].

Words used in this Notice have the meaning given to them in the Option
Agreement.

                      Number of Options being exercised: .

                      Number of Option Securities to be issued to Aviron .


DATED [#]



SIGNED   for   and   on   behalf   of           )
AVIRON by its duly authorised representatives:  )
                                                )



----------------------------------           -----------------------------------


----------------------------------           -----------------------------------
Print Name                                   Print Name


<PAGE>   62
                                    Page 30


                                   ANNEXURE B

                                 BUY-OUT NOTICE





To:        CSL Limited
           45 Poplar Road
           PARKVILLE   VIC   3052



TAKE NOTICE that AVIRON (AVIRON) exercises the right to receive a cash amount in
accordance with Clause [7.1, 7.2 OR 7.3] of the Option Agreement made on [#]
1998 between CSL LIMITED (CSL) and Aviron and requires CSL to pay Aviron the
cash amount as calculated in accordance with Clause 7 of the Option Agreement.



DATED [#]



SIGNED   for   and   on   behalf   of             )
AVIRON by its duly authorised representatives:    )
                                                  )


----------------------------------           -----------------------------------


----------------------------------           -----------------------------------
Print Name                                   Print Name



<PAGE>   63
                                    Page 31


                                   ANNEXURE C

                                 GRANT OF OPTION


To:        Aviron
           Attention:  Chief Executive Officer
           297 North Bernardo Avenue
           MOUNTAIN VIEW, CALIFORNIA  94043



In accordance with Clause 2.1 [(a) or (b) or (c)] of the Option Agreement made
on [ ] 1998 between CSL Limited (CSL) and Aviron (AVIRON), CSL hereby grants to
Aviron with effect on and from [date] the option to subscribe for and be
allotted [insert relevant number] of the Option Securities at any time during
the [insert relevant period] in accordance with the Option Agreement.


DATED [#]


SIGNED  for and on behalf of                          )
CSL LIMITED by its duly authorised representatives:   )
                                                      )

----------------------------------           -----------------------------------
Signature                                    Signature



----------------------------------           -----------------------------------
Print Name                                   Print Name


<PAGE>   64
                                    Page 32

                                   ANNEXURE D

                               FIRB BUY-OUT NOTICE





To:        CSL Limited
           45 Poplar Road
           PARKVILLE   VIC   3052



TAKE NOTICE that AVIRON (AVIRON) exercises the right to receive a cash amount in
accordance with Clause [10.1, 10.2 OR 10.3] of the Option Agreement made on [#]
June 1998 between CSL LIMITED (CSL) and Aviron and requires CSL to pay Aviron
the cash amount as calculated in accordance with Clause 10 of the Option
Agreement.



DATED [#]



SIGNED   for   and   on   behalf   of            )
AVIRON by its duly authorised representatives:   )
                                                 )


----------------------------------           -----------------------------------


----------------------------------           -----------------------------------
Print Name                                   Print Name


<PAGE>   65
                                    Page 33



                                            CERTAIN CONFIDENTIAL INFORMATION
                                            CONTAINED IN THIS DOCUMENT, MARKED
                                            BY BRACKETS, HAS BEEN OMITTED AND
                                            FILED WITH THE SECURITIES AND
                                            EXCHANGE COMMISSION PURSUANT TO RULE
                                            24B-2 OF THE SECURITIES EXCHANGE ACT
                                            OF 1934, AS AMENDED.




                                   CSL LIMITED
                                (ACN 051 588 348)



                                       and



                                     AVIRON










                                OPTION AGREEMENT



<PAGE>   66
                                     Page 2


                          ARTHUR ROBINSON & HEDDERWICKS
                                    Melbourne
                                   Ref MD:CBP
                                  Tel 9614 1011



<PAGE>   67


                                TABLE OF CONTENTS


<TABLE>
<S>                                                                        <C>
1. DEFINITIONS AND INTERPRETATION ......................................... 1
     1.1 Definitions ...................................................... 1
     1.2 Interpretation ................................................... 3

2. AGREEMENT TO GRANT OPTIONS ............................................. 4
     2.1 Agreement to grant Options ....................................... 4
     2.2 Limitation ....................................................... 4
     2.3 Grant of Options ................................................. 4
     2.4 Avoidance of Doubt ............................................... 4
     2.5 Grant of Alternative Options ..................................... 5
     2.6 Undertaking by CSL ............................................... 5

3. EXERCISE OF THE OPTIONS ................................................ 5
     3.1 Exercise by Notice ............................................... 5
     3.2 Contents of notice ............................................... 5
     3.3 Regulatory requirements .......................................... 5

4. COMPLETION ............................................................. 5
     4.1 Place of Completion .............................................. 5
     4.2 Payment of the Option Price ...................................... 5
     4.3 Issue of shares .................................................. 6
     4.4 Actions after Completion ......................................... 6

5. WARRANTY, UNDERTAKING AND COVENANTS BY CSL ............................. 6
     5.1 Unissued authorised share capital ................................ 6
     5.2 Undertaking by CSL ............................................... 6
     5.3 Covenants ........................................................ 6

6. EFFECT OF REORGANISATION ............................................... 6

7. BUY-OUT RIGHTS ......................................................... 6
     7.1 Application Period Option ........................................ 6
     7.2 Acceptance Period Option ......................................... 7
     7.3 Third Period Option .............................................. 8
     7.4 Method of Payment ................................................ 8
     7.5 Effect of court declaration ...................................... 9

8. ACKNOWLEDGEMENT ........................................................ 9

9. WITHHOLDING TAX ........................................................ 9
     9.1 Obligation to pay ................................................ 9
     9.2 Additional gross-up payment ...................................... 9
     9.3 [           * * *          ] ..................................... 9

</TABLE>

---------

[ *** ] = Confidential treatment requested.


                                       1.

<PAGE>   68

<TABLE>
<S>                                                                                  <C>
     9.4 If the Acceptance Period does not commence within [     * * *     ] ........ 9
     9.5 Meaning of net cost ....................................................... 10

10. FIRB BUY-OUT RIGHTS ............................................................ 10
     10.1 Application Period Option ................................................ 10
     10.2 Acceptance Period Option ................................................. 10
     10.3 Third Period Option ...................................................... 11
     10.4 Method of Payment ........................................................ 12

11. FURTHER ASSURANCES ............................................................. 12

12. RESOLUTION OF DISPUTES ......................................................... 12
     12.1 Reference to Expert ...................................................... 12
     12.2 Expert's instructions .................................................... 12
     12.3 Procedure ................................................................ 12
     12.4 Conclusiveness of report ................................................. 12
     12.5 Costs .................................................................... 12

13. ENTIRE AGREEMENT ............................................................... 13

14. NOTICES ........................................................................ 13

15. AMENDMENT ...................................................................... 13

16. ASSIGNMENT ..................................................................... 14

17. COUNTERPARTS ................................................................... 14

18. COSTS .......................................................................... 14

19. GOVERNING LAW AND JURISDICTION ................................................. 14

ANNEXURE A Option Notice ........................................................... 15

ANNEXURE B Buy-Out Notice .......................................................... 16

ANNEXURE C Grant of option ......................................................... 17

ANNEXURE D FIRB Buy-Out Notice ..................................................... 18

</TABLE>

                                       2.

<PAGE>   69


                                  SCHEDULE 14.2

                               [ * ] CSL PRODUCTS



                                       1.