GUARANTY

      FOR VALUE RECEIVED, the sufficiency of which is hereby acknowledged,  and,
in  consideration  of any credit and/or  financial  accommodation  heretofore or
hereafter from time to time made or granted to North American  Vaccine,  Inc., a
Canadian  corporation  ("BORROWER"),  by BANK OF  AMERICA,  N.A.  and any  other
subsidiaries  or affiliates of  BankAmerica  Corporation  and its successors and
assigns (collectively  "LENDER"),  [*], a Delaware corporation (the "GUARANTOR")
hereby  furnishes its guaranty of the  Guaranteed  Obligations  (as  hereinafter
defined) as follows:

      1.  GUARANTY. Guarantor hereby absolutely and unconditionally guarantees,
as a guarantee of payment and not merely as a guarantee of collection, prompt
payment when due, whether at stated maturity, upon acceleration or otherwise,
and at all times thereafter, of any and all existing and future indebtedness and
liabilities of every kind, nature and character, direct or indirect, absolute or
contingent, liquidated or unliquidated, voluntary or involuntary, of Borrower to
Lender arising under that certain letter loan agreement dated November 1, 1999
between Borrower and Lender (the "BORROWER CREDIT AGREEMENT") and all
instruments, agreements and other documents (including without limitation the
Security Agreement and the IP Security Agreement) of every kind and nature now
or hereafter executed in connection with the Borrower Credit Agreement
(including all renewals, extensions and modifications thereof and all costs,
structuring fees, attorneys' fees and expenses incurred by Lender in connection
with the collection or enforcement thereof) (collectively, the "GUARANTEED
OBLIGATIONS"). Lender's books and records showing the amount of the Guaranteed
Obligations shall be admissible in evidence in any action or proceeding, and
shall be binding upon Guarantor and serve as a rebuttable presumption in favor
of Lender for the purpose of establishing the amount of the Guaranteed
Obligations, subject only to manifest error. This Guaranty shall not be affected
by the genuineness of the Borrower Credit Agreement or the validity, regularity
or enforceability of the Guaranteed Obligations or any instrument or agreement
evidencing any Guaranteed Obligations, or by the existence, validity,
enforceability, perfection, or extent of any collateral therefor, or by any fact
or circumstance relating to the Guaranteed Obligations which might otherwise
constitute a defense to the obligations of Guarantor under this Guaranty. The
obligations of Guarantor hereunder shall be limited to an aggregate amount equal
to the largest amount that would not render its obligations hereunder subject to
avoidance under Section 548 of the Bankruptcy Code (Title 11, United States
Code) or any comparable provisions of any applicable state law.

      2.  NO DEDUCTIONS. All payments by Guarantor hereunder shall be paid in
full, without setoff or counterclaim or any deduction or withholding whatsoever,
including, without limitation, for any and all present and future taxes. In the
event that Guarantor or Lender is required by law to make any such deduction or
withholding, Guarantor agrees to pay on behalf of Lender such amount directly to
the appropriate person or entity, or if the Guarantor cannot legally comply with
the foregoing, Guarantor shall pay to Lender such additional amounts as will
result in the receipt by Lender of the full amount payable hereunder. Guarantor
shall promptly provide Lender with evidence of payment of any such amount made
on Lender's behalf.

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

*  Confidential treatment requested.

<PAGE>

      3.  NO TERMINATION. This Guaranty is a continuing and irrevocable guaranty
of all Guaranteed Obligations now or hereafter existing and shall remain in full
force and effect until all Guaranteed Obligations and any other amounts payable
under this Guaranty are indefeasibly paid and performed in full and any
commitments of Lender or facilities provided by Lender with respect to the
Guaranteed Obligations are terminated.

      4.  WAIVER OF NOTICES. Guarantor waives notice of the acceptance of this
Guaranty and of the extension or continuation of the Guaranteed Obligations or
any part thereof, subject to the provisions of Section 6. Guarantor further
waives presentment, protest, notice, dishonor or default, demand for payment and
any other notices to which Guarantor might otherwise be entitled as a condition
to the satisfaction of its obligations hereunder; provided that Lender shall
provide notice of any Event of Default (as defined in the Borrower Credit
Agreement) in accordance with the terms of Section 23 hereof.

      5.  SUBROGATION. Guarantor shall exercise no right of subrogation,
contribution or similar rights with respect to any payments it makes under this
Guaranty until (a) all of the Guaranteed Obligations and any amounts payable
under this Guaranty are indefeasibly paid and performed in full and any
commitments of Lender or facilities provided by Lender with respect to the
Guaranteed Obligations are terminated or (b) Guarantor exercises Guarantor's
Call Option (or Lender exercises Lender's Put Option) in accordance with and as
more specifically described in Section 23 hereof. If any amounts are paid to
Guarantor in violation of the foregoing limitation, then such amounts shall be
held in trust for the benefit of Lender and shall forthwith be paid to Lender to
reduce the amount of the Guaranteed Obligations, whether matured or unmatured.

      6.  WAIVER OF SURETYSHIP DEFENSES. Guarantor agrees that Lender may, at
any time and from time to time, and without notice to Guarantor, make any
agreement with Borrower or with any other person or entity liable on any of the
Guaranteed Obligations or providing collateral as security for the Guaranteed
Obligations, for the extension, renewal, payment, compromise, discharge or
release of the Guaranteed Obligations, or for any modification or amendment of
the terms thereof or of any instrument or agreement evidencing the Guaranteed
Obligations or the provision of collateral, all without in any way impairing,
releasing, discharging or otherwise affecting the obligations of Guarantor under
this Guaranty; provided that Lender shall not (a) extend the final maturity date
of the Guaranteed Obligations or any portion thereof, (b) reduce the rate or
extend the time for payment of interest, (c) waive the principal amount of any
Loan, (d) increase the Commitment or (e) release all or substantially all of any
collateral given to secure the Guaranteed Obligations, without in each case the
written consent of Guarantor. Guarantor waives any defense arising by reason of
any disability or other defense of Borrower or any other guarantor, or the
cessation from any cause whatsoever of the liability of Borrower, or any claim
that Guarantor's obligations exceed or are more burdensome than those of
Borrower and waives the benefit of any statute of limitations affecting the
liability of Guarantor hereunder. Guarantor waives any right to enforce any
remedy which Lender now has or may hereafter have against Borrower and waives
any benefit of and any right to participate in any security now or hereafter
held by Lender, subject to the provisions of Sections 23 and 24 hereof. Further,
Guarantor consents to the taking of, or failure to take, any action which might
in any manner or to any extent vary the risks of Guarantor under this Guaranty


                                       2
<PAGE>


or which, but for this provision, might operate as a discharge of Guarantor.

      7.  EXHAUSTION OF OTHER REMEDIES NOT REQUIRED. The obligations of
Guarantor hereunder are those of primary obligor, and not merely as surety, and
are independent of the Guaranteed Obligations. Guarantor waives diligence by
Lender and action on delinquency in respect of the Guaranteed Obligations or any
part thereof, including, without limitation any provisions of law requiring
Lender to exhaust any right or remedy or to take any action against Borrower,
any other guarantor or any other person, entity or property before enforcing
this Guaranty against Guarantor.

      8.  REINSTATEMENT. Notwithstanding anything in this Guaranty to the
contrary, this Guaranty shall continue to be effective or be reinstated, as the
case may be, if at any time any payment of any portion of the Guaranteed
Obligations is revoked, terminated, rescinded or reduced or must otherwise be
restored or returned upon the insolvency, bankruptcy or reorganization of
Borrower or any other person or entity or otherwise, as if such payment had not
been made and whether or not Lender is in possession of or has released this
Guaranty and regardless of any prior revocation, rescission, termination or
reduction.

      9.  SUBORDINATION. Guarantor hereby subordinates the payment of all
obligations and indebtedness of Borrower owing to Guarantor, whether now
existing or hereafter arising, including but not limited to any obligation of
Borrower to Guarantor as subrogee of Lender or resulting from Guarantor's
performance under this Guaranty, to the indefeasible payment in full of all
Guaranteed Obligations. If Lender so requests, any such obligation or
indebtedness of Borrower to Guarantor shall be enforced and performance received
by Guarantor as trustee for Lender and the proceeds thereof shall be paid over
to Lender on account of the Guaranteed Obligations, but without reducing or
affecting in any manner the liability of Guarantor under this Guaranty.

      10. INFORMATION. Guarantor agrees to furnish promptly to Lender any and
all financial or other information regarding Guarantor or its property as Lender
may reasonably request in writing; provided, Guarantor shall not be obligated to
furnish or deliver information to Lender in addition to the requirements set
forth in the Existing Credit Agreement (as defined in Section 20 hereof).

      11. STAY OF ACCELERATION. In the event that acceleration of the time for
payment of any of the Guaranteed Obligations is stayed, upon the insolvency,
bankruptcy or reorganization of Borrower or any other person or entity, or
otherwise, all such amounts shall nonetheless be payable by Guarantor
immediately upon demand by Lender.

      12. EXPENSES. Guarantor shall pay on demand all out-of-pocket expenses
(including reasonable attorneys' fees and expenses and the allocated cost and
disbursements of internal legal counsel) in any way relating to the enforcement
or protection of Lender's rights under this Guaranty, including any incurred in
the preservation, protection or enforcement of any rights of Lender in any case
commenced by or against Guarantor under the Bankruptcy Code (Title 11, United


                                       3
<PAGE>

States Code) or any similar or successor statute. The obligations of Guarantor
under the preceding sentence shall survive termination of this Guaranty.

      13. AMENDMENTS. No provision of this Guaranty may be waived, amended,
supplemented or modified, except by a written instrument executed by Lender and
Guarantor.

      14. NO WAIVER. No failure by Lender to exercise, and no delay in
exercising, any right, remedy or power hereunder shall operate as a waiver
thereof; nor shall any single or partial exercise of any right, remedy or power
hereunder preclude any other or further exercise thereof or the exercise of any
other right. The remedies herein provided are cumulative and not exclusive of
any remedies provided by law or in equity. The unenforceability or invalidity of
any provision of this Guaranty shall not affect the enforceability or validity
of any other provision herein.

      15. ASSIGNMENT; GOVERNING LAWS; JURISDICTION. This Guaranty shall (a) bind
Guarantor and its successors and assigns, PROVIDED that Guarantor may not assign
its rights or obligations under this Guaranty without the prior written consent
of Lender (and any attempted assignment without such consent shall be void), (b)
inure to the benefit of Lender and its successors and assigns and Lender may,
without notice to Guarantor and without affecting Guarantor's obligations
hereunder, assign or sell participations in the Guaranteed Obligations and this
Guaranty, in whole or in part, and (c) be governed by the internal laws of the
State of New York. Guarantor hereby irrevocably (i) submits to the non-exclusive
jurisdiction of any United States Federal or State court sitting in New York,
New York in any action or proceeding arising out of or relating to this
Guaranty, and (ii) waives to the fullest extent permitted by law any defense
asserting an inconvenient forum in connection therewith. Service of process by
Lender in connection with such action or proceeding shall be binding on
Guarantor if sent to Guarantor by registered or certified mail at its address
specified below. Guarantor agrees that Lender may disclose to any prospective
purchaser and any purchaser of all or part of the Guaranteed Obligations any and
all information in Lender's possession concerning Guarantor, this Guaranty and
any security for this Guaranty.

      16. CONDITION OF BORROWER. Guarantor acknowledges and agrees that it has
the sole responsibility for, and has adequate means of, obtaining from Borrower
such information concerning the financial condition, business and operations of
Borrower as Guarantor requires, and that Lender has no duty, and Guarantor is
not relying on Lender at any time to disclose to Guarantor any information
relating to the business, operations or financial condition of Borrower.

      17. SETOFF. If and to the extent any payment is not made when due
hereunder, Lender may setoff and charge from time to time any amount so due
against any or all of Guarantor's accounts or deposits with Lender.

      18. OTHER GUARANTEES. Unless otherwise agreed by Lender and Guarantor in
writing, this Guaranty is not intended to supersede or otherwise affect any
other guaranty now or hereafter given by Guarantor for the benefit of Lender or
any term or provision thereof.


                                       4
<PAGE>


      19. REPRESENTATIONS AND WARRANTIES. Guarantor represents and warrants that
(i) it is duly organized and in good standing under the laws of the jurisdiction
of its organization and has full capacity and right to make and perform this
Guaranty, and all necessary authority has been obtained; (ii) this Guaranty
constitutes its legal, valid and binding obligation enforceable in accordance
with its terms; (iii) the making and performance of this Guaranty does not and
will not violate the provisions of any applicable law, regulation or order, and
does not and will not result in the breach of, or constitute a default or
require any consent under, any agreement, instrument, or document to which it is
a party or by which it or any of its property may be bound or affected; (iv) all
consents, approvals, licenses and authorizations of, and filings and
registrations with, any governmental authority required under applicable law and
regulations for the making and performance of this Guaranty have been obtained
or made and are in full force and effect; (v) by virtue of its relationship with
Borrower, the execution, delivery and performance of this Guaranty is for the
direct benefit of Guarantor and it has received adequate consideration for this
Guaranty; and (vi) the financial information that has been delivered to Lender
by or on behalf of Guarantor is complete and correct in all respects and
accurately presents the financial condition and the operational results of
Guarantor and since the date of the most recent financial statements delivered
to Lender, there has been no material adverse change in the financial or
operational condition of Guarantor.

      20. INCORPORATION OF COVENANTS. Reference is made to that certain Credit
Agreement (Facility A) dated as of November 24, 1998 (as amended or modified
prior to the date of the Guaranty, the "EXISTING CREDIT AGREEMENT") among
Guarantor, the financial institutions named therein, Bank of America, N.A.
(formerly Bank of America National Trust and Saving Association) and The Chase
Manhattan Bank, as Co-Arrangers, and The First National Bank of Chicago, as
administrative agent. Reference is further made to the covenants contained in
Article VIII of the Existing Credit Agreement (hereinafter referred to as the
"INCORPORATED COVENANTS"). So long as principal of and interest on any Loan (as
defined in the Borrower Credit Agreement) or any other amount payable under the
Borrower Credit Agreement or under any other Loan Document remains unpaid or
unsatisfied or the Commitment (as defined in the Borrower Credit Agreement) has
not been terminated, Guarantor shall comply with the Incorporated Covenants, it
being agreed that such covenants and agreements shall survive any termination,
cancellation or discharge of the Existing Credit Agreement. Guarantor agrees
with Lender that the Incorporated Covenants (and all other relevant provisions
of the Existing Credit Agreement related thereto, including without limitation
all exhibits, schedules and the defined terms contained in Section 1.01 thereof,
which are used in the Incorporated Covenants) are hereby incorporated by
reference into this Guaranty to the same extent and with the same effect as if
set forth fully herein and shall inure to the benefit of Lender, without giving
effect to any waiver, amendment, modification or replacement of the Existing
Credit Agreement or any term or provision of the Incorporated Covenants
occurring subsequent to the date of this Guaranty, except to the extent
otherwise specifically provided for in the following paragraph of this Section.

      In the event a waiver is granted under the Existing Credit Agreement or an
amendment or modification is executed with respect to the Existing Credit
Agreement, and such waiver, amendment and/or modification affects the


                                       5
<PAGE>

Incorporated Covenants, then such waiver, amendment or modification shall be
effective with respect to the Incorporated Covenants as incorporated by
reference into this Guaranty only if consented to in writing by the Lender. In
the event of any replacement of the Existing Credit Agreement with a similar
credit facility (the "NEW FACILITY") the covenants contained in the New Facility
which correspond to the covenants contained in Sections 8.01 and 8.02,
respectively, of the Existing Credit Agreement shall become the Incorporated
Covenants hereunder only if consented to in writing by Lender and, if such
consent is not granted or if the Existing Credit Agreement is terminated and not
replaced, then covenants contained in Sections 8.01 and 8.02, respectively, of
the Existing Credit Agreement (together with any modifications or amendments
approved in accordance with this paragraph) shall continue to be the
Incorporated Covenants hereunder.

      21. GUARANTY EVENTS OF DEFAULT. Each of the following shall be a "Guaranty
Event of Default" for purposes of this Guaranty:

      (a)            Any "Event of Default" specified in Section 9.01 of the
                Existing Credit Agreement occurs and is continuing, without
                giving effect to any waiver thereof pursuant to the Existing
                Credit Agreement; or
      (b)            Guarantor fails to perform or observe any other covenant or
                agreement  (not  specified  in  (a)  above)  contained  in  this
                Guaranty or any Loan Document (as defined in the Borrower Credit
                Agreement)  on its part to be performed or observed  (including,
                without limitation,  the failure of Guarantor to comply with any
                of its payments  obligations  in  accordance  with and under the
                terms of this Guaranty); or
      (c)            Any representation or warranty in this Guaranty or in any
                certificate, agreement, instrument or other document made or
                delivered by Guarantor pursuant to or in connection with this
                Guaranty or the Borrower Loan Agreement proves to have been
                incorrect when made or deemed made.


      22. WAIVER OF JURY TRIAL; FINAL AGREEMENT. TO THE EXTENT ALLOWED BY
APPLICABLE LAW, GUARANTOR AND LENDER EACH WAIVE TRIAL BY JURY WITH RESPECT TO
ANY ACTION, CLAIM, SUIT OR PROCEEDING ON OR ARISING OUT OF THIS GUARANTY. THIS
GUARANTY REPRESENTS THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE
CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS BETWEEN THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN
THE PARTIES.

      23. CALL/PUT PROVISIONS.

      (a) GUARANTOR'S CALL OPTION. Guarantor (or any Affiliate identified by
      Guarantor) shall have the right, upon three Business Days' prior written
      notice to Lender, to purchase all (but not less than all) of Lender's
      rights, interests and obligations in and to the Borrower Credit Agreement
      at par value and subject in all cases to the representations, warranties


                                       6
<PAGE>

      and disclaimers set forth in Section 24 hereof (as set forth herein,
      "GUARANTOR'S CALL OPTION"). Notwithstanding (I) Guarantor's exercise of
      its call option pursuant to this section or (II) any other provision of
      this Guaranty to the contrary, the Guaranty shall continue to be effective
      or be reinstated, as the case may be, if at any time any payment of any
      portion of the Guaranteed Obligations received by Lender is (x) revoked,
      terminated, rescinded or reduced or (y) subject to a request or an action
      filed by Borrower, or any of its successors in bankruptcy (including a
      trustee or any official committee), seeking the return or restoration of
      any or all of such payment pursuant to the avoidance provisions of the
      United States Bankruptcy Code, specifically including but not limited to
      11 U.S.C. ss.ss. 544, 547, 548 and 550, as if such payment had not been
      made and whether or not Lender is in possession of or has released this
      Guaranty and regardless of any prior revocation, rescission, termination
      or reduction. Guarantor shall be responsible for all costs and expenses
      (including without limitation Breakage Costs) associated with Guarantor's
      exercise of its rights hereunder.

      (b) LENDER'S PUT OPTION. Upon the occurrence of any Event of Default and
      written notice thereof provided by Lender to Guarantor, Lender shall sell
      to Guarantor all (but not less than all) of Lender's rights, interests and
      obligations in and to the Borrower Credit Agreement at par value and
      subject in all cases to the representations, warranties and disclaimers
      set forth in Section 24 hereof (as set forth herein, "LENDER'S PUT
      OPTION"). Notwithstanding (I) Lender's exercise of its put option pursuant
      to this section or (II) any other provision of this Guaranty to the
      contrary, the Guaranty shall continue to be effective or be reinstated, as
      the case may be, if at any time any payment of any portion of the
      Guaranteed Obligations is (x) revoked, terminated, rescinded or reduced or
      (y) subject to a request or an action filed by Borrower, or any of its
      successors in bankruptcy (including a trustee or any official committee),
      seeking the return or restoration of any or all of such payment pursuant
      to the avoidance provisions of the United States Bankruptcy Code,
      specifically including but not limited to 11 U.S.C. ss.ss. 544, 547, 548
      and 550, as if such payment had not been made and whether or not Lender is
      in possession of or has released this Guaranty and regardless of any prior
      revocation, rescission, termination or reduction. Guarantor shall be
      responsible for all costs and expenses (including without limitation
      Breakage Costs) associated with Lender's exercise of its rights hereunder.

      PROVIDED, HOWEVER, that, (a) notwithstanding Borrower's and Guarantor's
good faith efforts, if the Guarantor and Borrower do not execute a definitive
agreement for the North American Vaccine Acquisition on or prior to November 16,
1999, and (b) between the date hereof and November 16, 1999, Borrower has not,
directly or indirectly solicited, initiated or encouraged (including by way of
furnishing or disclosing nonpublic information) any inquiries or the making or
any proposal or offer (including, without limitation, any offer to its
stockholders), with any third party other than Guarantor relating to any Company
Competing Transaction or knowingly encouraged or otherwise entered into or
maintained any discussions or negotiations with respect to any Company Competing
Transaction, or agreed or endorsed any agreement, arrangement or understanding
with respect to a Company Competing Transaction, or authorized or permitted any
representative of Borrower to take any such action, then Guarantor agrees that
it shall not, in connection with the exercise of Guarantor's Call Option or the

                                       7
<PAGE>

exercise of Lender's Put Option, commence the exercise of remedies set forth in
the Borrower Credit Agreement if Borrower repays all amounts owing under or in
connection with the Borrower Credit Agreement and any related agreements within
20 days thereafter. For purposes of this Guaranty, a "Company Competing
Transaction" shall mean any of the following involving Borrower:

           (i)     any merger, consolidation, share exchange, recapitalization,
business combination, material issuance of equity or other similar transaction;

           (ii)    any sale, lease, exchange, transfer or other disposition of
10% or more of the assets of Borrower and its subsidiaries taken as a whole in a
single transaction or series of related transactions;

           (iii)   any license, sublicense, sale or similar transaction,
arrangement or agreement with respect to any material patents, trademarks, trade
secrets, patent applications, know how or other intellectual property of
Borrower or any of its subsidiaries;

           (iv)    any tender offer or exchange offer for any of the outstanding
voting securities of Borrower;

           (v)     any acquisition by any person or group of persons of 10% or
more of the voting securities (or securities convertible or exchangeable
therefor)of Borrower; or

           (vi)    any public announcement of a proposal, plan or intention to
do any of the foregoing or any agreement to engage in any of the foregoing.

      24. ASSIGNMENT PROVISIONS. To the extent that Borrower's obligations under
the Borrower Credit Agreement are secured by a lien or pledge of collateral to
Lender in Borrower's property or assets (of whatever nature) (collectively,
"BORROWER COLLATERAL"), Lender hereby agrees that upon payment in full by
Guarantor of the Guaranteed Obligations (as determined by Lender), Lender shall,
if requested in writing by Guarantor, assign to Guarantor or its designee all or
a portion of Lender's rights (if any, and of whatever nature) in and to such
Borrower Collateral. Lender does not make, shall not be obligated to make nor
shall be deemed to have made any representation or warranty of any kind as to
the value of the Borrower Collateral or any portion thereof, including but not
limited to any representation or warranty with respect to the value of Lender's
Lien in such Borrower Collateral or the attachment, perfection or priority of
Lender's Lien with respect thereto. Lender hereby specifically disclaims any
such representations or warranties. Lender shall not warrant nor be obligated to
defend Lender's Lien or the attachment, perfection or priority of such Lien.
GUARANTOR HEREBY SPECIFICALLY ACKNOWLEDGES AND AGREES THAT LENDER DOES NOT MAKE,
SHALL NOT BE OBLIGATED TO MAKE NOR SHALL BE DEEMED TO HAVE MADE ANY
REPRESENTATION OR WARRANTY WITH RESPECT TO THE BORROWER COLLATERAL, INCLUDING
WITHOUT LIMITATION THE ATTACHMENT, PERFECTION OR PRIORITY OF LENDER'S LIEN WITH
RESPECT THERETO. Lender agrees to reasonably cooperate with Guarantor to execute
UCC assignments and such other legal documentation as may be necessary to effect


                                       8
<PAGE>

the purposes of this paragraph. Guarantor shall be responsible for the costs and
expenses (including without limitation reasonable attorneys' fees and expenses
and the allocated cost and disbursements of internal legal counsel) associated
with the assignment and/or transfer by Lender of its rights with respect to the
Borrower Collateral in accordance with the terms hereof.

      25. DEFINED TERMS. Capitalized terms used herein but not otherwise defined
shall have the respective meaning set forth in the Borrower Credit Agreement.



                                       9
<PAGE>



Duly executed and delivered under seal this 1st day of November, 1999.


                                   [*]




Acknowledged and Agreed:

BANK OF AMERICA, N.A.

By:    /s/ Lawrence J. Gordon
       ----------------------

Name:  Lawrence J. Gordon

Title: Vice President


Acknowledged and Agreed:

NORTH AMERICAN VACCINE, INC.

By:    /s/ Randal Chase
       -----------------------

Name:  Randal Chase, Ph.D.
       -------------------
Title: Chief Executive Officer & President
       -----------------------------------

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*  Confidential treatment requested.





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