<PAGE>   1
================================================================================

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                ----------------
                                  FORM 10-K/A
                               (Amendment No. 1)
                                ----------------

(MARK ONE)

     [X]   ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
           SECURITIES EXCHANGE ACT OF 1934

                   FOR THE FISCAL YEAR ENDED DECEMBER 31, 2000

                                       OR

     [ ]   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
           SECURITIES EXCHANGE ACT OF 1934

                FOR THE TRANSITION PERIOD         TO         .

                         COMMISSION FILE NUMBER: 0-20815

                                     AVIRON
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

                DELAWARE                               77-0309686
     (STATE OR OTHER JURISDICTION OF                (I.R.S. EMPLOYER
     INCORPORATION OR ORGANIZATION)                IDENTIFICATION NO.)

           297 NORTH BERNARDO AVENUE, MOUNTAIN VIEW, CALIFORNIA 94043
           (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES INCLUDING ZIP CODE)

                                 (650) 919-6500
              (REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE)

           SECURITIES REGISTERED PURSUANT TO SECTION 12(b) OF THE ACT
                                      NONE

           SECURITIES REGISTERED PURSUANT TO SECTION 12(g) OF THE ACT
                          COMMON STOCK, $.001 PAR VALUE

    Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
Registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes [X] No [ ]

    Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of Registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K. [ ]

     Based on the closing sale price of $46.77 on April 27, 2001, the aggregate
market value of the voting stock held by non-affiliates of the Registrant was
$1,407,196,070.

     On April 27, 2001, there were outstanding 30,600,493 shares of the
Registrant's Common Stock.

                       DOCUMENTS INCORPORATED BY REFERENCE
                        (TO THE EXTENT INDICATED HEREIN)

================================================================================
<PAGE>   2
                                    PART III.

ITEM 10. DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT

DIRECTORS

        C. BOYD CLARKE, age 52, has been our President and Chief Executive
Officer since December 1999. He has been a director since December 1999 and our
Chairman since January 2001. From 1998 until joining us, Mr. Clarke was Chief
Executive Officer and President of U.S. Bioscience, Inc., a biotechnology
company. Mr. Clarke served as President and Chief Operating Officer of U.S.
Bioscience, Inc. from 1996 to 1998. From 1977 to 1996, Mr. Clarke held a number
of positions at Merck & Co., Inc., including being the first president of
Pasteur-Merieux MSD, and most recently as Vice President of Merck Vaccines. Mr.
Clarke has a B.S. in Biochemistry, and an M.A. in History from the University of
Calgary.

        WAYNE T. HOCKMEYER, PH.D., age 56, became a member of our Board of
Directors in March 2000. Dr. Hockmeyer founded MedImmune, Inc., a biotechnology
company, in April 1988 as President and Chief Executive Officer and was elected
to serve on its board of directors in May 1988. He became Chairman of the board
of directors of MedImmune, Inc. in May 1993. Dr. Hockmeyer relinquished his
position as Chief Executive Officer of MedImmune, Inc. in October 2000 and
currently serves as its Chairman. Prior to founding MedImmune, Inc., Dr.
Hockmeyer served as a commissioned officer in the United States Army from 1966
to 1986. From 1980 to 1986 he was Chairman of the Department of Immunology at
the Walter Reed Army Institute of Research. In 1986, Dr. Hockmeyer joined Praxis
Biologics, Inc. as Vice President of Research and Development, and was there
until founding MedImmune, Inc. in 1988. Dr. Hockmeyer is a member of the
Maryland Economic Development Commission and the Maryland Technology Development
Corporation. He is a member of the board of directors of Digene Corporation,
Intermune Pharmaceuticals, Inc., GenVec, Inc. and Advanced Pharma, Inc. Dr.
Hockmeyer also is a member of the board of directors of the Biotechnology
Industry Organization and the Technology Council of Maryland, a member of the
Board of Visitors of the University of Maryland Biotechnology Institute and the
Board of Advisors of the Institute of Human Virology. Dr. Hockmeyer received a
B.S. degree from Purdue University and a Ph.D. from the University of Florida.

        BERNARD ROIZMAN, SC.D., age 72, has been a member of our Board of
Directors since 1992. Dr. Roizman has been the Joseph Regenstein Distinguished
Service Professor of Virology at the University of Chicago since 1984. He holds
B.A. and M.S. degrees from Temple University and an Sc.D. from The Johns Hopkins
University. Dr. Roizman is also a member of our Scientific Advisory Board.

        DENNIS M. FENTON, PH.D., age 49, became a member of our Board of
Directors in March 2000. In February 2000 Dr. Fenton was appointed Executive
Vice President of Amgen, a biotechnology company. From January 1995 to February
2000, Dr. Fenton served as Senior Vice President, Operations of Amgen. From
August 1992 to January 1995, Dr. Fenton served as Senior Vice President, Sales
and Marketing of Amgen. Dr. Fenton served as Amgen's Vice President, Process
Development, Facilities and Manufacturing Services, from 1991 to 1992. Dr.
Fenton previously had served as Vice President, Pilot Plant Operations and
Clinical Manufacturing, from 1988 to 1991, and as Director, Pilot Plant
Operations, from 1985 to 1988. Dr. Fenton received a B.A. from Manhattan College
in New York and a Ph.D. in Microbiology from Rutgers University.

        ALAN C. MENDELSON, age 53, has been a member of our Board of Directors
since April 2000 and was our Secretary since our inception until April 2000. Mr.
Mendelson is a senior partner of Latham & Watkins and has been with the firm
since May 2000. Prior to joining Latham & Watkins, Mr. Mendelson was a senior
partner at Cooley Godward, LLP, where he had practiced law since 1973. Mr.
Mendelson served as Secretary and Acting General Counsel of Amgen, Inc. from
April 1990 to April 1991 and as Acting General Counsel of Cadence Design
Systems, Inc. from November 1995 to June 1996. Mr. Mendelson serves as the
secretary of a number of private and public companies and is a member of the
board of directors of Axys Pharmaceuticals, Inc., Valentis, Inc. and US
Search.com, Inc. Mr. Mendelson received an A.B. in Political Science from the
University of California, Berkeley and a J.D. from Harvard Law School.

        J. LEIGHTON READ, M.D., age 50, founder of Aviron, was our Chairman from
1992 until January 2001, Chief Executive Officer from 1992 until 1999 and Chief
Financial Officer from 1992 until 1996. In 1989, he co-founded Affymax N.V. with
Dr. Alejandro Zaffaroni, serving initially as its Executive Vice President and
Chief Operating Officer and later, from 1990 to 1991, as President of the Pharma
Division and as a Managing Director of the parent company. From 1991 to 1993,
Dr. Read was a principal with Interhealth Limited, an investment partnership.
Prior to 1989, Dr. Read held appointments at the Harvard Medical School and
School of Public Health. He has served on the boards of a number of private
biotechnology companies and is currently on the board of CV Therapeutics, Inc.
and AxyS Pharmaceuticals, Inc., both of which are biotechnology companies. Dr.
Read holds a B.S. in Biology and Psychology from Rice University and an M.D.
from the University of Texas Health Science Center at San Antonio.

        R. GORDON DOUGLAS, M.D., age 67, became a member of our Board of
Directors in August 2000. Dr. Douglas currently serves as a consultant to the
Vaccine Research Center at the National Institutes of Health, or NIH. Prior to
this role, he served as President of Merck Vaccines from 1991 until 1999. From
1982 to 1990, Dr. Douglas served as Professor of Medicine and Chairman of the
Department of Medicine at Cornell University Medical College and
Physician-in-Chief at New York Hospital. Between 1970 and 1982, Dr. Douglas held
a variety of roles at the University of Rochester School of Medicine. Dr.
Douglas is Chairman of the board of directors at VICAL, Inc. and serves on
several other boards of directors at biotechnology and non-profit associations
focused on infectious diseases, world health, vaccines and pharmaceutical
developments. Dr. Douglas holds an A.B. from Princeton University and an M.D.
from Cornell University Medical College.

EXECUTIVE OFFICERS

    The names of our executive officers as of March 22, 2001 and information
about them is presented below.


<TABLE>
<CAPTION>
       NAME                             AGE                                  POSITION
       ----                             ---                                  --------
<S>                                     <C>   <C>
       EXECUTIVE OFFICERS

       C. Boyd Clarke.................  52    Chief Executive Officer, President and Chairman
       Edward J. Arcuri, Ph.D.........  50    Senior Vice President, Operations
       Charlene A. Friedman...........  43    Vice President, General Counsel and Secretary
       Harry B. Greenberg, M.D........  56    Senior Vice President, Research and Development and Chief Scientific Officer
       Fred Kurland...................  51    Senior Vice President and Chief Financial Officer
       Carol A. Olson.................  43    Senior Vice President, Commercial Development
       Rayasam S. Prasad..............  48    Senior Vice President, Technical Affairs
</TABLE>

    C. Boyd Clarke has been our President and Chief Executive Officer since
December 1999. He has been a director since December 1999 and our Chairman since
January 2001. From 1998 until joining us, Mr. Clarke was Chief Executive Officer
and President of U.S. Bioscience, Inc., a biotechnology company. Mr. Clarke
served as President and Chief Operating Officer of U.S. Bioscience from 1996 to
1998. From 1977 to 1996, Mr. Clarke held a number of positions at Merck & Co.,
Inc., including being the first president of Pasteur-Merieux MSD, and most
recently as Vice President of Merck Vaccines. Mr. Clarke has a B.S. in
Biochemistry and an M.A. in History from the University of Calgary.

    Edward J. Arcuri, Ph.D., has been our Senior Vice President, Operations
since May 2000. He joined Aviron as Vice President, Manufacturing in July 1999.
Dr. Arcuri joined us from North American Vaccine, Inc., or NAVA, where he served
as Vice President, Manufacturing Operations and Process Development from January
1995 to July 1999. Prior to joining NAVA, Dr. Arcuri served as Senior Director,
Biological Manufacturing at Merck & Co., Inc. from 1991 to 1994. Dr. Arcuri
holds a B.S. degree in Biology from the State University of New York at Albany
and a masters degree and Ph.D. in Biology from Rensselaer Polytechnic Institute.

    Charlene A. Friedman has been our Vice President, General Counsel and
Secretary since April 2000. From 1999 until joining us, Ms. Friedman was a
consultant to Inamed Corporation, a medical device company. From 1996 to 1999,
Ms. Friedman held various positions at Collagen Aesthetics, Inc., a
biotechnology company, most recently as Vice President, Legal and Regulatory
Affairs, General Counsel and Assistant Secretary. From 1995 to 1996, Ms.
Friedman was an attorney with Lillick & Charles in San Francisco, California.
From 1993 to 1995, she practiced law in Boston, Massachusetts at Warner &
Stackpole. She is a member of the Massachusetts and California bars. Ms.
Friedman holds a B.A. in Ancient Greek and Latin from Tufts University and a
J.D. from Northeastern University.

    Harry B. Greenberg, M.D., has been our Senior Vice President, Research and
Development and Chief Scientific Officer since November 2000. Dr. Greenberg
joined us from the Stanford University School of Medicine, where he spent 17
years as a faculty member. He was most recently the Senior Associate Dean for
Research and the Joseph D. Grant Endowed Professor of Medicine. He also was
serving as Associate Chief of Staff for Research at the Veterans Administration
Palo Alto Health Care System. Dr. Greenberg served as chair of the Vaccines and
Related Biological Products Advisory Committee of the U.S. Food and Drug
Administration from February 1999 until beginning his position with Aviron. Dr.
Greenberg holds a B.A. in History with honors from Dartmouth College and an M.D.
from Columbia College of Physicians and Surgeons.


<PAGE>   3
    Fred Kurland has been our Senior Vice President and Chief Financial Officer
since January 1998. Prior to joining us, Mr. Kurland was Vice President and
Chief Financial Officer of Protein Design Labs, Inc., a biotechnology company,
from 1996 to 1998. From 1995 to 1996, Mr. Kurland was Vice President and Chief
Financial Officer at Applied Immune Sciences, a biotechnology company, and from
1981 to 1995, he held a number of positions at Syntex Corporation, a
pharmaceutical company, most recently as Vice President and Controller. Mr.
Kurland, a Certified Public Accountant, holds a B.S. in Business and Economics
from Lehigh University, and an M.B.A. and a J.D. from the University of Chicago.

    Carol A. Olson has been our Senior Vice President, Commercial Development
since May 1998. Prior to joining us, Ms. Olson was the founder and managing
director of the Churchill Madison Group, a management consulting firm focused on
building new businesses in the medical, life sciences and high technology
industries. From 1984 to 1993, Ms. Olson worked for the Hewlett Packard Company.
Ms. Olson holds a B.A. in Economics with honors from Yale University and an
M.B.A. from Stanford University.

    Rayasam S. Prasad has been our Senior Vice President, Technical Affairs
since January 2001 and prior to that had been our Vice President, Technical
Affairs since September 1999. Mr. Prasad joined Aviron from Chiron Vaccines, the
global vaccines business unit of Chiron Corporation, a biotechnology company,
where he served as Head of Regulatory, Quality and Drug Safety. Mr. Prasad also
served as Director of Quality Assurance for Therapeutics and Vaccines at Chiron.
He was with Chiron from October 1994 to September 1999. Prior to joining Chiron,
Mr. Prasad held positions in quality assurance and biological manufacturing
operations at Genentech, Inc. from 1986 to 1994, and Burroughs Wellcome Co. from
1981 to 1986. Mr. Prasad holds a B.S. in Pharmacy from

SECTION 16(a) BENEFICIAL OWNERSHIP REPORTING COMPLIANCE

        Section 16(a) of the Securities Exchange Act requires our directors and
executive officers, and persons who own more than 10 percent of a registered
class of our equity securities, to file with the SEC initial reports of
ownership and reports of changes in ownership of common stock and other equity
securities of Aviron. Officers, directors and greater than 10 percent
stockholders are required by SEC regulation to furnish us with copies of all
Section 16(a) forms they file.

        Based solely on a review of the copies of such reports furnished to us
or written representations that no other reports were required, we believe that
during the fiscal year ended December 31, 2000, all Section 16(a) filing
requirements applicable to our officers, directors and greater than 10 percent
beneficial owners were complied with, except for the following reports. All
directors except for Dr. Read and Mr. Clarke were granted options effective
December 31, 2000. However, because the directors granted options did not
receive their grant documents until March 2001, they filed Forms 5 in respect of
the grants in April 2001. Also, Ms. Olson filed a late report with respect to an
option granted to her in February 2000.

<PAGE>   4
ITEM 11. EXECUTIVE COMPENSATION

COMPENSATION OF DIRECTORS

        Since June 1998, each of our non-employee directors has received cash
compensation for their services, in addition to being eligible for reimbursement
for their expenses incurred in connection with attendance at Board and Committee
meetings in accordance with our policy. In March 2000, the Board approved
increases in the cash compensation paid to each non-employee director. The
retainer was increased from $1,000 per month to $1,250 per month. Compensation
paid for each Board meeting attended was increased from $500 to $2,500.
Compensation for each Committee meeting attended was increased from $300 to
$500. In addition, a non-employee director who participates in a Board or
Committee meeting telephonically shall receive compensation in the amount of 50
percent of the applicable meeting fee provided the Board or Committee meeting
lasts at least 30 minutes. Should a Committee meeting fall on the same date as a
Board meeting, such non-employee director shall receive only the Board meeting
attendance stipend of $2,500.

        Each of our non-employee directors also receives stock option grants
under the 1996 Non-Employee Directors' Stock Option Plan. The maximum number of
shares of common stock that may be issued pursuant to options granted under the
Directors' Plan is 350,000. The Directors' Plan is administered by the Board of
Directors, unless the Board delegates administration to a Committee comprised of
not less than two members of the Board.

        During fiscal year 2000, we granted annual options under the Directors'
Plan covering 10,000 shares to both of Mr. Klingenstein and Dr. Roizman, 8,384
shares to both of Drs. Fenton and Hockmeyer, 6,849 shares to Mr. Mendelson and
3,562 shares to Dr. Douglas, all at an exercise price per share of $66.8125, the
fair market value of such common stock on the date of grant. The number of
shares granted were based on the length of the period in 2000 during which each
was a non-employee director. Also during the last fiscal year, we granted
initial grants of options covering 20,000 shares to each of Dr. Douglas, Dr.
Fenton, Dr. Hockmeyer and Mr. Mendelson. The exercise price per share was the
fair market value of such common stock on the date of each grant: $40.5625 for
both of Drs. Fenton and Hockmeyer; $24.25 for Mr. Mendelson; and $41.9375 for
Dr. Douglas. As of March 31, 2001, options for an aggregate of 6,990 shares of
our common stock have been exercised under the Directors' Plan.

COMPENSATION OF EXECUTIVE OFFICERS

                             SUMMARY OF COMPENSATION

        The following table shows for the fiscal years ended December 31, 2000,
December 31, 1999, and December 31, 1998, compensation awarded or paid to, or
earned by, our Chief Executive Officer and for each of our four most highly
compensated executive officers who were serving as executive officers at the end
of fiscal year 2000.



<PAGE>   5

                           SUMMARY COMPENSATION TABLE


<TABLE>
<CAPTION>
                                                                                                                 LONG-TERM
                                                                                                                COMPENSATION
                                                                                                                   AWARDS
                                                                          ANNUAL COMPENSATION              ------------------------
                                                            --------------------------------------------   SECURITIES
                                                                                            OTHER ANNUAL   UNDERLYING   ALL OTHER
      NAME AND PRINCIPAL POSITION                            YEAR     SALARY     BONUS (1) COMPENSATION(2)  OPTIONS    COMPENSATION
      ---------------------------                           ------   --------    --------  --------------  ----------  ------------
<S>                                                         <C>      <C>         <C>       <C>             <C>         <C>
       C. Boyd Clarke ...................................    2000    $340,000    $450,000    $    966             --    $142,930(3)
         Chairman, President and Chief Executive Officer     1999      24,628          --          --        600,000       5,025(4)
                                                             1998          --          --          --             --          --
       Edward J. Arcuri, Ph.D. ..........................    2000     247,856     112,500         773        125,000
         Senior Vice President, Operations                   1999     111,916      10,000          --             --          --
                                                             1998          --          --          --             --          --
       Harry B. Greenberg, M.D. .........................    2000      56,817      26,676          --        225,000      75,000(5)
         Senior Vice President, Research and                 1999          --          --          --             --          --
         Development, and Chief Scientific Officer           1998          --          --          --             --          --

       Fred Kurland .....................................    2000     252,350     100,960       1,233         75,000
         Senior Vice President and Chief Financial           1999     245,000      20,000       1,032         30,000
         Officer                                             1998     223,955      25,000         283        100,000

       Carol A. Olson ...................................    2000     257,500     115,875         521         75,000
         Senior Vice President, Commercial                   1999     250,000      20,000         354         60,000
         Development                                         1998     143,013      40,000          93        166,617
</TABLE>

----------

(1) Represents amounts paid in subsequent year relating to performance during
    the stated year.

(2) Represents amounts paid for group term life insurance.

(3) Represents payments for Mr. Clarke's expenses in relocating to California.
    In addition, Mr. Clarke received an interest-free secured loan of $500,000
    for purchase of a home in California.

(4) Represents payment of a housing allowance in the amount of $5,025.

(5) Represents a bonus paid to Dr. Greenberg at the time of commencement of his
    employment.


                        STOCK OPTION GRANTS AND EXERCISES

        The following tables show for the fiscal year ended December 31, 2000,
information regarding options granted to, and held at year end by the executive
officers listed in the "Summary Compensation Table" above.

                              OPTION GRANTS IN 2000

        The exercise price of each option was equal to the fair value of our
common stock as valued by the Board of Directors on the date of grant. The
exercise price may be paid in cash, in shares of our common stock valued at fair
value on the exercise date or through a cashless exercise procedure involving a
same-day sale of the purchased shares.

        The potential realizable value is calculated based on the 10 year term
of the option at the time of grant. Stock price appreciation of 5 percent and 10
percent is assumed pursuant to rules promulgated by the Securities and Exchange
Commission and does not represent our prediction of our stock price performance.
The potential realizable values at 5 percent and 10 percent appreciation are
calculated by:

        -       multiplying the number of shares of common stock subject to a
                given option by the exercise price per share;

        -       assuming that the aggregate stock value derived from that
                calculation compounds at the annual 5 percent or 10 percent rate
                shown in the table until the expiration of the options; and

        -       subtracting from that result the aggregate option exercise
                price.

The shares listed in the following table under "Number of Securities Underlying
Options Granted" are subject to vesting. Some of the stock options listed in the
table (other than the option held by Dr. Greenberg) vest and become exercisable
ratably over 50 months and some, granted in 2000, vest upon achievement of
milestones relating to performance goals for FluMist, our investigational
intranasal influenza vaccine. A portion of the options vested and became
exercisable upon the acceptance for review by the FDA of our BLA


<PAGE>   6

submission for FluMist on December 28, 2000. Another portion of the options will
vest and become exercisable at the earlier of the approval of FluMist for
marketing in the United States, or five years from the date of grant. Other
options will become exercisable when FluMist is approved for marketing in the
United States, but only if this event occurs in 2001; otherwise these options
will be canceled. The option for 225,000 shares held by Dr. Greenberg will vest
and become exercisable with respect to 42,000 shares on September 8, 2001, 3,500
shares each month for 38 months thereafter, and 50,000 shares upon the first to
occur of (1) the date on which FluMist is approved for marketing in the United
States and (2) September 8, 2005.

        Each of the options has a 10 year term, subject to earlier termination
if the optionee's service with us ceases. Upon termination of employment
following a change of control, the options may vest and become immediately
exercisable. Mr. Clarke's options were granted outside our 1996 Equity Incentive
Plan. See the section below entitled "Employment Agreements and Change in
Control Arrangements" for a description of our agreements with Mr. Clarke and
Dr. Greenberg concerning stock options that have been granted to them.

        Percentages shown under "Percent of Total Options Granted in 2000" are
based on 2,974,654 options granted to our employees during 2000.


<TABLE>
<CAPTION>
                                                                                                       POTENTIAL REALIZABLE
                                                              INDIVIDUAL GRANTS                          VALUE AT ASSUMED
                                          -------------------------------------------------------        ANNUAL RATES OF
                                          NUMBER OF                                                         STOCK PRICE
                                          SECURITIES      PERCENT OF                                      APPRECIATION FOR
                                          UNDERLYING     TOTAL OPTIONS                                      OPTION TERM
                                           OPTIONS        GRANTED IN     EXERCISE       EXPIRATION   --------------------------
        NAME                               GRANTED           2000         PRICE            DATE          5%             10%
        ----                              ----------     -------------   ---------      ----------   -----------    -----------
<S>                                       <C>            <C>             <C>            <C>          <C>            <C>
        C. Boyd Clarke ............              0               0              --             --             --             --
        Edward J. Arcuri, Ph.D. ...         45,000            1.51%      $  24.000       02/09/10    $   752,502    $ 1,837,957
                                            80,000            2.69%         24.250       04/26/10      1,146,747      2,975,136
        Harry B. Greenberg, M.D. ..        225,000            7.56%         41.875       09/08/10      6,566,708     16,037,304
        Fred Kurland ..............         75,000            2.52%         24.000       02/09/10      1,254,170      3,063,262
        Carol A. Olson ............         75,000            2.52%         24.000       02/09/10      1,254,170      3,063,262
</TABLE>


       AGGREGATE OPTION EXERCISES IN LAST FISCAL YEAR AND FISCAL YEAR-END
                                 OPTION VALUES

        The following table contains the aggregate number of shares of common
stock underlying options stock options exercised in the 2000 fiscal year and the
number of shares underlying stock options held by each named executive officer
as of December 31, 2000. Amounts shown under the column "Value Realized"
represent the difference between the market price of the common stock on the
exercises date and the option exercise price multiplied by the number of shares
acquired upon exercise. Amounts shown under the column "Value of Unexercised
In-the-Money Options at December 31, 2000" are based on the closing price of our
common stock ($66.8125) on December 29, 2000, as reported on the Nasdaq Stock
Market, without taking into account any taxes that may be payable in connection
with the transaction, multiplied by the number of shares underlying the option,
less the exercise price payable for these shares.

<TABLE>
<CAPTION>
                                                                   NUMBER OF SECURITIES
                                  SHARES                          UNDERLYING UNEXERCISED          VALUE OF UNEXERCISED
                                ACQUIRED ON      VALUE                 OPTIONS AT                 IN-THE-MONEY OPTIONS
                                EXERCISE (#)    REALIZED           DECEMBER 31, 2000              AT DECEMBER 31, 2000
                                ------------  -----------      ----------------------------   -----------------------------
NAME                                                           EXERCISABLE    UNEXERCISABLE   EXERCISABLE     UNEXERCISABLE
----                                                           -----------    -------------   ------------    -------------
<S>                             <C>           <C>              <C>            <C>             <C>             <C>
C. Boyd Clarke ............         5,965     $   276,657         114,034         480,001     $ 5,708,542     $24,028,849
Edward J. Arcuri, Ph.D. ...            --              --          45,600         154,400       1,938,968       6,570,216
Harry B. Greenberg, M.D. ..            --              --             720         225,000          47,322       5,610,375
Fred Kurland ..............            --              --         103,900         101,100       4,393,733       4,303,565
Carol A. Olson ............        10,857         436,204         157,940         143,600       6,673,254       6,172,496
</TABLE>



<PAGE>   7

            EMPLOYMENT AGREEMENTS AND CHANGE IN CONTROL ARRANGEMENTS

        In December 1999, we entered into an Executive Severance Benefits
Agreement with Mr. Clarke, our President and Chief Executive Officer, providing
that, in the event Mr. Clarke is terminated without cause, he will receive one
year's salary, bonus, health coverage and continued vesting of his stock options
for up to one year. In the event Mr. Clarke is terminated following a change in
control of Aviron, he will receive two years' salary, bonus, health coverage,
full vesting and immediate exercisability of his stock options and other
severance payments.

        In December 1999, we entered into a Non-Officer Chairman Employment
Agreement with Dr. Read. The terms of this agreement provided for compensation
to be paid to Dr. Read in exchange for his continuing services to us as Chairman
of our Board of Directors. This compensation included an annual salary of
$300,000, provided that Dr. Read devoted at least 20 hours a week to his
position as Chairman. Dr. Read also was eligible for the standard benefits
package we offer to our employees and the agreement provided for acceleration of
the vesting of all his stock options upon a change in control of Aviron. The
term of the agreement was December 6, 1999 through December 31, 2000.

        In April 2000, our Board of Directors adopted management continuity
agreements for our executive officers and members of senior management, other
than Mr. Clarke. These agreements are intended to provide our executive officers
and members of senior management with financial security and sufficient income
and encouragement to remain with Aviron through a change of control of the
company. If within 18 months of a change of control, the individual's employment
is terminated, actually or constructively, the agreements will provide: (a) for
a lump sum salary payment equal to the sum of (1) the individual's base annual
salary rate in effect immediately preceding the date of the change of control,
and (2) the individual's target bonus for the fiscal year in which the change of
control occurs, (b) that all outstanding stock options for the individual will
vest and become immediately exercisable, and (c) that the individual will be
entitled (but not obligated) to continue health care coverage for one year and
at the individual's own expense for an additional six months. If pursuant to a
change of control, the acquiring company does not assume or substitute the
individual's outstanding stock options, then the vesting and exercisability of
such stock options will accelerate.

        In October 2000, we entered into an Executive Severance Benefits
Agreement with Dr. Greenberg, our Senior Vice President, Research and
Development, and Chief Scientific Officer, providing that, in the event Dr.
Greenberg is terminated without cause, he will receive six months' salary,
bonus, health coverage and continued vesting of his stock options for up to six
months. In the event Dr. Greenberg is terminated following a change in control
of Aviron, he will receive one year's salary, bonus, health coverage and full
vesting and immediate exercisability of his stock options.

        "Change of Control" under the management continuity agreements and the
agreements with Dr. Greenberg and Mr. Clarke means:

        -       a dissolution or liquidation of Aviron;

        -       a sale, lease or other disposition of all or substantially all
                of our assets;

        -       a merger or consolidation in which beneficial ownership of the
                surviving entity or its parent ceases to be represented by
                securities of Aviron representing at least sixty percent (60%)
                of the total voting power of Aviron immediately prior to such
                transaction;

        -       an acquisition by any entity (other than specified affiliated
                entities) of beneficial ownership, directly or indirectly, of
                securities of the Company representing at least forty percent
                (40%) of the combined voting power of the Company's then
                outstanding securities; or

        -       incumbent directors (including directors whose election or
                nomination was approved by at least 40% of the incumbent
                directors) cease to constitute at least 40% of the members of
                our Board of Directors.



<PAGE>   8

         REPORT OF THE COMPENSATION COMMITTEE OF THE BOARD OF DIRECTORS
                            ON EXECUTIVE COMPENSATION

COMPENSATION COMMITTEE REPORT

        The Board of Directors maintains a Compensation Committee composed of
three non-employee directors. The Committee is responsible for establishing our
compensation programs for all employees, including executives. For executive
officers, the Committee evaluates performance and determines compensation
policies and levels.

COMPENSATION PHILOSOPHY

        The goals of the compensation program are to align compensation with
business objectives and performance and to enable us to attract, retain and
reward executive officers and other key employees who contribute to our
long-term success and to motivate them to enhance long-term stockholder value.
Key elements of this philosophy are:

        -       We pay competitively with other biotechnology companies with
                which we compete for talent. To ensure that pay is competitive,
                we compare our pay practices with these companies and set our
                pay parameters based on this review.

        -       We provide significant equity-based incentives for executives
                and other key employees to ensure that they are motivated over
                the long term to respond to our business challenges and
                opportunities as owners and not just as employees.

        Salary. The Committee annually reviews each executive officer's salary.
When reviewing salaries, the Committee considers individual and corporate
performance, levels of responsibility, prior experience, breadth of knowledge
and competitive pay practices.

        Cash Bonus. We established a bonus plan in January 1998 and the
Committee annually reviews each executive officer's bonus, our aggregate bonus
pool and the bonus allocations by employee position. Payment of cash bonuses is
tied to the accomplishment of specific corporate milestones set at the beginning
of the year and to each individual officer's year-end performance review.

        Equity Incentives. Our equity incentive program consists of the 1996
Equity Incentive Plan, the 1999 Non-Officer Equity Incentive Plan and the 1996
Employee Stock Purchase Plan. The option program utilizes vesting periods
(generally four years) to encourage key employees to continue in our employ. In
2000, we granted options which vest based on specific performance-based
milestones. Through option grants, executives receive significant equity
incentives to build long-term stockholder value. Grants are made at 100 percent
of fair market value on the date of grant. Executives receive value from these
grants only if our common stock appreciates over the long term. The size of
option grants is determined based on competitive practices in the biotechnology
industry and our philosophy of significantly linking executive compensation with
stockholder interests. The Committee believes this approach creates an
appropriate focus on longer term objectives and promotes executive retention.
The Board granted options to purchase an aggregate of 500,000 shares of our
common stock to the executive officers listed in the "Summary Compensation
Table" during 2000.

        We established the Employee Stock Purchase Plan both to encourage
employees to continue in our employ and to motivate employees through ownership
interest in Aviron. Under the Purchase Plan, employees, including officers, may
have up to 15 percent of their earnings withheld for purchases of common stock
on certain dates specified by the Board. The price of common stock purchased
will be equal to 85 percent of the lower of the fair market value of the common
stock on the relevant purchase date or commencement date of the relevant
offering period. There were 2 offerings during fiscal 2000.

CHIEF EXECUTIVE OFFICER COMPENSATION

        Mr. Clarke's salary during 2000 as President and Chief Executive Officer
was $340,000. Following the Committee's review of Aviron's performance against
corporate milestones for 2000 and Mr. Clarke's performance during 2000, the
Committee awarded Mr. Clarke a 2000 merit bonus of $350,000 and an additional
bonus in the amount of $100,000, and increased his salary for 2001 to $450,000.
In determining Mr. Clarke's 2001 salary, the Committee took into account (1) the
performance of Mr. Clarke and the Company during 2000, (2) the scope of Mr.
Clarke's responsibilities, and (3) the Board's confidence in Mr. Clarke to lead
the Company towards its corporate milestones for 2001.



<PAGE>   9

FEDERAL TAX CONSIDERATIONS

        Section 162(m) of the Internal Revenue Code limits us to a deduction for
federal income tax purposes of no more than $1 million of compensation paid to
certain executive officers in a taxable year. Compensation above $1 million may
be deducted if it is "performance-based compensation" within the meaning of the
Code.

        The statute containing this law and the applicable Treasury regulations
offer a number of transitional exceptions to this deduction limit for
pre-existing compensation plans, arrangements and binding contracts. As a
result, the Committee believes that at the present time it is quite unlikely
that the compensation paid to any executive officer in a taxable year that is
subject to the deduction limit will exceed $1 million. Therefore, the Committee
has not yet established a policy for determining which forms of incentive
compensation awarded to our executive officers shall be designed to qualify as
"performance-based compensation." The Committee intends to continue to evaluate
the effects of the statute and any applicable Treasury regulations and to comply
with Code Section 162(m) in the future to the extent consistent with the best
interests of Aviron.

CONCLUSION

        Through the plans described above, a significant portion of our
compensation program and Mr. Clarke's compensation are contingent on our
performance, and realization of benefits is closely linked to increases in
long-term stockholder value. We remain committed to this philosophy of pay for
performance, recognizing that the competitive market for talented executives and
the volatility of our business may result in highly variable compensation for a
particular time period.



Wayne T. Hockmeyer, Ph.D., Compensation Committee Member
Paul H. Klingenstein, Compensation Committee Member
R. Gordon Douglas, M.D., Compensation Committee Member

          Compensation Committee Interlocks and Insider Participation

     During fiscal 2000, the Compensation Committee was initially composed of
two non-employee directors: Dr. Jane E. Shaw and Mr. Klingenstein. In April
2000, Dr. Shaw resigned from our Board of Directors and the Board appointed Dr.
Hockmeyer to the Compensation Committee. In February 2001, Dr. Douglas was
appointed to the Compensation Committee. In April 2001, Mr. Klingenstein
resigned from our Board of Directors and Dr. Fenton was appointed to the
Compensation Committee.



<PAGE>   10

PERFORMANCE MEASUREMENT COMPARISON

        The following graph shows the total stockholder return of an investment
of $100 in cash on November 5, 1996 for:

        -       our common stock;

        -       the Nasdaq Stock Market-U.S. Index; and

        -       the Nasdaq Pharmaceutical Index.

All values assume reinvestment of the full amount of all dividends and are
calculated as of December 31 of each year.




                              [PERFORMANCE GRAPH]




<TABLE>
<CAPTION>
                                                      Cumulative Total Return
                                  --------------------------------------------------------------
                                  11/5/96     12/96      12/97      12/98      12/99      12/00
<S>                               <C>         <C>        <C>        <C>        <C>        <C>
AVIRON                             100.00     93.75      339.06     323.44     197.66     835.16
NASDAQ STOCK MARKET (U.S.)         100.00     106.11     129.96     183.27     340.61     204.98
NASDAQ PHARMACEUTICAL              100.00     101.49     104.88     133.51     250.94     312.13
</TABLE>


This Section is not "soliciting material," is not deemed "filed" with the SEC
and is not to be incorporated by reference in any of our filings under the
Securities Act of 1933 or the Securities Exchange Act of 1934 whether made
before or after the date hereof and irrespective of any general incorporation
language in any such filing.



<PAGE>   11
ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

        The following table sets forth certain information regarding the
beneficial ownership of our common stock as of April 27, 2001, by:

        -       all those known by us to be beneficial owners of more than five
                percent of our common stock;

        -       each of our current directors and nominees;

        -       each of our executive officers; and

        -       all executive officers, current directors and nominees as a
                group.

        Beneficial ownership is determined in accordance with Rule 13d-3 under
the Securities and Exchange Act of 1934. In computing the number of shares
beneficially owned by a person and the percentage ownership of that person,
shares of common stock subject to options held by that person that are currently
exercisable or exercisable within 60 days of April 27, 2001 are deemed
outstanding. These shares, however, are not deemed outstanding for the purposes
of computing the percentage ownership of each other person. Percentage of
ownership is based on [30,591,904] shares of common stock outstanding on April
27, 2001. Unless otherwise indicated, the address of each of the individuals and
entities named below is: c/o Aviron, 297 North Bernardo Avenue, Mountain View,
CA 94043.

<TABLE>
<CAPTION>
                                                                        BENEFICIAL OWNERSHIP
                                                     -------------------------------------------------------
                                                                                NUMBER OF
                                                                                  SHARES
                                                        SHARES ISSUABLE         (INCLUDING
                                                      PURSUANT TO OPTIONS       NUMBER SHOWN
                                                     EXERCISABLE WITHIN 60       IN FIRST         PERCENTAGE
          BENEFICIAL OWNER                           DAYS OF APRIL 18, 2001       COLUMN)          OF TOTAL
          ----------------                           ----------------------     ------------      ----------
<S>                                                  <C>                        <C>               <C>
        5% STOCKHOLDER
        Biotech Invest, S.A.(1) ....................                 --          3,105,286          10.15%

        DIRECTORS AND EXECUTIVE OFFICERS
        C. Boyd Clarke .............................            174,034            179,999            *
        Edward J. Arcuri, Ph.D. ....................             67,600             67,600            *
        R. Gordon Douglas, Jr. M.D. ................                 --                 --            *
        Dennis M. Fenton, Ph.D. ....................              6,600              6,600            *
        Charlene A. Friedman .......................             33,060             33,549            *
        Harry B. Greenberg, M.D. ...................                720              6,624            *
        Wayne T. Hockmeyer, Ph.D. ..................              6,600              6,600            *
        Fred Kurland ...............................            118,900            121,031            *
        Alan C. Mendelson ..........................              6,600              9,443            *
        Carol A. Olson (2) .........................            180,440            196,311            *
        Rayasam Prasad .............................             46,960             48,242            *
        J. Leighton Read, M.D.(3) ..................            250,000            545,100           1.78%
        Bernard Roizman, Sc.D. .....................             19,000            194,000            *
        All directors and executive officers as a
          group (13 persons) .......................            910,514          1,415,099           4.63%
</TABLE>

 * Represents beneficial ownership of less than 1% of the outstanding shares of
our common stock.


(1)   Biotech Invest, S.A. is located at Swiss Bank Tower Panama 1, Republic of
      Panama

(2)   Includes 500 shares held by Carol A. Olson, custodian for John Gregory
      Olson (UCAUTMA). Ms. Olson disclaims beneficial ownership of the shares
      held by the trust.

(3)   Includes 32,000 shares owned by the minor children of Dr. Read.
<PAGE>   12
ITEM 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

        We have entered into indemnity agreements with our executive officers
and directors and members of senior management which provide, among other
things, that we will indemnify these persons, under the circumstances and to the
extent provided for therein, for expenses, damages, judgments, fines and
settlements he or she may be required to pay in actions or proceedings which he
or she is or may be made a party by reason of his or her position as a director,
officer or other agent of Aviron, and otherwise to the full extent permitted
under Delaware law and our Bylaws.

        On January 13, 2000, we entered into a loan agreement with Mr. Clarke
for an interest-free secured loan of $500,000 to assist him in purchasing a home
in California. The loan is repayable over five years and as of April 18, 2001,
the amount outstanding was $500,000.

        On October 12, 2000, we sold 450,000 shares of our common stock in a
private transaction to Biotech Invest, S.A., an entity that holds of record or
beneficially more than 5% of our common stock, at a price of $48.00 per share
for proceeds of $21.6 million. On April 9, 2001, we filed a registration
statement registering the offer and resale of those shares by Biotech Invest,
S.A.

        Alan Mendelson, a member of our Board of Directors, is a senior partner
of the law firm Latham & Watkins, which firm has provided us with general legal
representation since November 2000.
<PAGE>   13
                                    PART IV.

ITEM 14. EXHIBITS, FINANCIAL STATEMENT SCHEDULES, AND REPORTS ON FORM 8-K

(a) (3) EXHIBITS

    See Exhibit Index.


<PAGE>   14
                                   SIGNATURES

    Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, as amended, the Registrant has duly caused this Amendment
No. 1 to the Registrant's Annual Report on Form 10-K/A to be signed on its
behalf by the undersigned, thereunto duly authorized, on April 30, 2001.


                                        AVIRON

                                        By:      /s/   C. BOYD CLARKE
                                            ------------------------------------
                                                       C. Boyd Clarke
                                                  Chairman, President and
                                                   Chief Executive Officer

    In accordance with the requirements of the Securities Exchange Act of 1934,
as amended, this Amendment No. 1 to the Registrant's Annual Report on Form
10-K/A has been signed below by the following persons on behalf of the
Registrant in the capacities and on the dates stated.

<TABLE>
<CAPTION>
                     SIGNATURE                                                  TITLE                              DATE
                     ---------                                                  -----                              ----
<S>                                                        <C>                                                 <C>
               /s/   C. BOYD CLARKE                        Chairman, President, and Chief Executive Officer    April 30, 2001
----------------------------------------------------                (Principal Executive Officer)
                  C. Boyd Clarke

                /s/   FRED KURLAND                                    Senior Vice President and                April 30, 2001
----------------------------------------------------                  Chief Financial Officer
                   Fred Kurland                              (Principal Financial and Accounting Officer)


                      *                                                         Director                       April 30, 2001
----------------------------------------------------
           R. Gordon Douglas, Jr., M.D.

                      *                                                         Director                       April 30, 2001
---------------------------------------------------
              Dennis M. Fenton, Ph.D.

                      *                                                         Director                       April 30, 2001
----------------------------------------------------
             Wayne T. Hockmeyer, Ph.D.


                      *                                                         Director                       April 30, 2001
----------------------------------------------------
                 Alan C. Mendelson

                      *                                                         Director                       April 30, 2001
----------------------------------------------------
              J. Leighton Read, M.D.

                      *                                                         Director                       April 30, 2001
----------------------------------------------------
              Bernard Roizman, Sc.D.

           * By: /s/   C. BOYD CLARKE
---------------------------------------------------
                   C. Boyd Clarke
                  Attorney-in-fact

</TABLE>

<PAGE>   15

                                  EXHIBIT INDEX

<TABLE>
<CAPTION>
ITEM                                  DESCRIPTION
----                                  -----------
<S>       <C>
   3.1    Bylaws of the Registrant(1).

   3.2    Amended and Restated Certificate of Incorporation of the Registrant(1).

   3.3    Certificate of Amendment of Amended and Restated Certificate of
          Incorporation(2).

   4.1    Reference is made to Exhibits 3.1 through 3.3.

   4.2    Specimen Stock Certificate.**

   4.3    Warrant for Series A Preferred Stock, issued to The Mount Sinai School
          of Medicine of the City of New York(3).

   4.4    Warrant for Series A Preferred Stock, issued to The Mount Sinai School
          of Medicine of the City of New York(3).

   4.5    Warrant for Series A Preferred Stock, issued to The Mount Sinai School
          of Medicine of the City of New York(3).

   4.6    Warrant for Series A Preferred Stock, issued to The Mount Sinai School
          of Medicine of the City of New York(3).

   4.7    Warrant for Series C Preferred Stock, issued to Raymond, James &
          Associates(3).

   4.8    Amended and Investors Rights Agreement, dated July 18, 1995, among the
          Registrant and the investors named therein(3).

   4.9    Common Stock Purchase Agreement between the Registrant and Biotech
          Target, S.A., dated as of March 27, 1997(4).

   4.10   Rights Agreement between the Registrant and BankBoston, N.A., dated as
          of October 8, 1997(5).

   4.11   Common Stock Purchase Agreement between the Registrant and American
          Home Products Corporation, dated as of December 16, 1999(6).

   4.12   Common Stock Purchase Agreement between the Registrant and American
          Home Products Corporation, dated as of December 30, 1999(6).

   4.13   Common Stock Purchase Agreement between the Registrant and American
          Home Products Corporation, dated as of February 3, 2000(6).

   4.14   Warrant for Common Stock, issued to University of Michigan(6).

   4.15   Common Stock Purchase Agreement between the Registrant and American
          Home Products Corporation, dated as of April 5, 2000(7).

   4.16   Registration Rights Agreement dated October 10, 2000, by and between
          the Company and Evans Vaccines Limited(8).

   4.17   Common Stock Purchase Agreement between the Registrant and Biotech
          Invest, S.A., dated as of October 10, 2000.**

   4.18   Warrant for Common Stock, issued to ARCH Development Corporation(9).

   4.19   Warrant for Common Stock, issued to The Proctor and Gamble
          Company(10).

   4.20   Warrants for Common Stock, issued to Evans Vaccines Limited(11).

   4.21   Indenture entered into between Aviron and Marine Midland Bank, as
          Trustee, dated March 15, 1998(12).
</TABLE>

<PAGE>   16

<TABLE>
<CAPTION>
ITEM                                  DESCRIPTION
----                                  -----------
<S>       <C>
   4.22   Indenture entered into between Aviron and HSBC Bank USA as Trustee,
          dated February 7, 2001.**

   4.23   Officer's Certificate pursuant to Section 2.01 of the Subordinated
          Indenture, dated February 7, 2001.**

   4.24   Amendment No. 1 to Common Stock Purchase Agreement, dated as of June
          9, 2000, by and between Acqua Wellington North American Equities Fund
          Ltd. and the Company(13).

 +10.1    License Agreement between the Registrant and ARCH Development
          Corporation, dated July 1992(3).

 +10.2    Technology Transfer Agreement between the Registrant and The Mount
          Sinai School of Medicine of the City University of New York, dated
          February 9, 1993(3).

 +10.3    Materials Transfer and Intellectual Property Agreement between the
          Registrant and the Regents of the University of Michigan, dated
          February 24, 1995(3).

  10.4    Stock Transfer Agreement between the Registrant and the Regents of the
          University of Michigan, dated February 24, 1995(3).

 +10.5    Development and License Agreement between the Registrant and Sang-A
          Pharm. Co., Ltd., dated May 3, 1995(3).

 +10.6    Cooperative Research and Development Agreement between the Registrant
          and the National Institutes of Health, dated May 30, 1995(3).

 +10.7    Heads of Agreement between the Registrant and SmithKline Beecham
          Biologicals S.A., dated October 8, 1995(14).

  10.8    First Amendment to Facility Reservation Agreement, dated as of August
          1, 2000, by and between Aviron and Packaging Coordinators, Inc.(15).

 *10.9    1996 Equity Incentive Plan, as amended as of June 1, 2000(16).

 *10.10   1996 Non-Employee Directors' Stock Option Plan, as amended as of
          June 1, 2000(17).

 *10.11   1996 Employee Stock Purchase Plan, as amended as of June 4, 1998(18).

  10.12   Industrial Lease between the Registrant and the Vanni Business Park
          General Partnership, dated August 29, 1995(3).

 +10.13   First Amendment to License Agreement between the Registrant and ARCH
          Development Corporation dated March 15, 1996(14).

 +10.14   Biological Materials License Agreement between the Registrant and
          the National Institutes of Health, dated May 31, 1996(14).

++10.15   Amended and Restated Production Agreement, dated as of August 1, 2000,
          by and between Aviron and Packaging Coordinators, Inc.(19)(20).

 +10.16   Production Agreement between the Registrant and Packaging
          Coordinators, Inc., dated as of October 31, 1997(21).

  10.17   Facility Reservation Agreement between the Registrant and Packaging
          Coordinators, Inc., dated as of October 31, 1997(21).

 +10.18   Influenza Vaccine Collaboration and License Distributor Agreement
          between the Registrant and CSL Limited, dated June 19, 1998(22).

 +10.19   Supply Agreement between the Registrant and Becton Dickinson and
          Company dated July 1, 1998(23).

 +10.20   United States License and Co-Promotion Agreement between the
          Registrant and Wyeth Lederle Vaccines dated January 11, 1999(24).

 +10.21   International FluMist(TM) License Agreement between the Registrant
          and Wyeth dated January 11, 1999(24).
</TABLE>

<PAGE>   17

<TABLE>
<CAPTION>
ITEM                                  DESCRIPTION
----                                  -----------
<S>       <C>
 +10.22   FluMist(TM) Supply Agreement between the Registrant and Wyeth
          Lederle Vaccines dated January 11, 1999(24).

 +10.23   Credit Agreement between the Registrant and American Home Products
          Corporation dated January 11, 1999(24).

 +10.24   Letter Amendment to the Materials Transfer and Intellectual Property
          Agreement between the Registrant and the Regents of the University of
          Michigan dated February 24, 1999(25).

  10.25   Real Property Lease by and between the Registrant and Spieker
          Properties, L.P. dated February 5, 1999(26).

 +10.26   First Amendment to the Influenza Vaccine Collaboration and License
          and Distribution Agreement by and between the Registrant and CSL
          Limited, A.C.N. dated June 7, 1999(26).

  10.27   Loan and Security Agreement by and between the Registrant and
          Transamerica Business Credit Corporation dated June 23, 1999(26).

  10.28   Master Loan and Security Agreement by and between the Registrant and
          FINOVA Capital Corporation dated July 23, 1999(27).

 *10.29   Form of Management Continuity Agreement(28).

  10.30   Real Property Lease by and between the Registrant and MELP VII L.P.,
          dated October 20, 1999(6).

 *10.31   Offer Letter, as amended, by and between the Registrant and C. Boyd
          Clarke, dated November 22, 1999(6).

 *10.32   Employment Agreement by and between the Registrant and J. Leighton
          Read, dated December 6, 1999(6).

  10.33   Amendment No. 1 to Stock Transfer Agreement by and between the
          Registrant and The Regents of the University of Michigan, dated
          February 16, 2000(6).

 *10.34   Executive Severance Benefits Agreement by and between the Registrant
          and Harry Greenberg, dated October 23, 2000.**

 *10.35   1999 Non-Officer Equity Incentive Plan, as amended as of July 26, 2000(29).

 *10.36   Stock Option Agreement for C. Boyd Clarke(30).

++10.38   Agreement for Lease of AVU Premises at Gaskill Road, Speke, dated
          October 11, 2000.**

++10.39   Underlease of AVU Premises at Gaskill Road Speke, dated October 11, 2000.**

++10.40   Agreement for Lease of AVU Extension Premises at Gaskill Road Speke,
          dated October 11, 2000.**

++10.41   Underlease of AVU Extension Premises at Gaskill Road Speke, dated
          October 11, 2000.**

++10.42   Agreement for the Sale and Purchase of Leasehold Property know as Plot 6
          Boulevard Industry Park, Halewood, Merseyside, dated October 10, 2000.**

++10.43   Underlease of Plot 6 Boulevard Industry Park Halewood Merseyside,
          dated February 17, 2000.**

++10.44   Master Agreement by and between Powderject Pharmaceuticals Limited,
          Evans Vaccines Limited, the Registrant and Aviron UK, dated
          October 11, 2000.**

++10.45   Agreement Relating to the Sharing and Provision of Certain Services,
          by and between Evans Vaccines Limited and Aviron UK Limited.**
</TABLE>

<PAGE>   18

<TABLE>
<CAPTION>
ITEM                                  DESCRIPTION
----                                  -----------
<S>       <C>
++10.46   Transfer Agreement by and between Evans Vaccines Limited and Aviron UK
          Limited, dated October 11, 2000.**

++10.47   Amended and Restated Contract Manufacture Agreement by and between
          Evans Vaccines Limited and the Registrant, dated October 11, 2000.**

++10.48   Know How Licence Agreement by and between Evans Vaccines Limited and
          Aviron UK Limited, dated October 11, 2000.**

  10.49   FluMist(TM) Supply Agreement Amendment, dated January 1, 2001.**

++10.50   Amendment Number One (1) to Cooperative Research and Development
          Agreement AI-000062, by and between NIAID and Aviron, dated as of
          August 3, 1999.**

++10.51   Amendment Number Two (2) to Cooperative Research and Development
          Agreement AI-000062, by and between NIAID and Aviron, dated as of June
          12, 2000.**

  21.1    Subsidiaries of Aviron.**

  23.1    Consent of Ernst & Young LLP, Independent Auditors.

  24.1    Power of Attorney. See Signature Page.**
</TABLE>
---------------
+    Confidential treatment has been granted for portions of this exhibit.

++   Confidential treatment has been requested for portions of this exhibit.

*    Compensatory Plan or Agreement.

**   Previously filed.

(1)  Incorporated by reference to the correspondingly numbered exhibit to our
     Quarterly Report on Form 10-Q for the quarter ended September 30, 1996,
     File No. 0-20815, filed December 20, 1996.

(2)  Incorporated by reference to Exhibit 3.3 to our Quarterly Report on
     Form 10-Q for the quarter ended June 30, 2000, File No. 0-20815, filed
     August 11, 2000.

(3)  Incorporated by reference to the correspondingly numbered exhibit to our
     Registration Statement on Form S-1, File No. 333-05209, filed June 5, 1996.

(4)  Incorporated by reference to the correspondingly numbered exhibit to our
     Quarterly Report on Form 10-Q for the quarter ended March 31, 1997, File
     No. 0-20815, filed May 15, 1997.

(5)  Incorporated by reference to Exhibit 99.2 to our Current Report on Form
     8-K, File No. 0-20815, filed October 10, 1997.

(6)  Incorporated by reference to the correspondingly numbered exhibit to our
     Annual Report on Form 10-K for the year ended December 31, 1999, File No.
     0-20815, filed March 8, 2000.

(7)  Incorporated by reference to the correspondingly numbered exhibit to our
     Quarterly Report on Form 10-Q for the quarter ended March 31, 2000, File
     No. 0-20815, filed May 15, 2000.

(8)  Incorporated by reference to Exhibit 4.16 to our Registration Statement on
     Form S-3/A, File No. 333-45072, filed October 24, 2000.

<PAGE>   19


(9)  Incorporated by reference to Exhibit 4.17 to our Quarterly Report on Form
     10-Q for the quarter ended June 30, 2000, File No. 0-20815, filed August
     11, 2000.

(10) Incorporated by reference to Exhibit 4.18 to our Quarterly Report on Form
     10-Q for the quarter ended September 30, 2000, File No. 0-20815, filed
     November 14, 2000.

(11) Incorporated by reference to Exhibits 4.19 through 4.24 to our Registration
     Statement on Form S-3, File No. 333-52028, filed December 18, 2000.

(12) Incorporated by reference to Exhibit 4.12 to our Registration Statement on
     Form S-3/A, File No. 333-41649, filed April 6, 1998.

(13) Incorporated by reference to Exhibit 4.1 to our Current Report on Form 8-K,
     File No. 0-20815, filed June 12, 2000.

(14) Incorporated by reference to the correspondingly numbered exhibit to our
     Registration Statement on Form S-1/A, File No 333-05209, filed June 20,
     1996.

(15) Incorporated by reference to Exhibit 10.32 to our Quarterly Report on Form
     10-Q for the quarter ended September 30, 2000, File No. 0-20815, filed
     November 14, 2000.

(16) Incorporated by reference to Exhibit 99.1 to our Registration Statement on
     Form S-8, File No. 333-44350, filed August 23, 2000.

(17) Incorporated by reference to Exhibit 99.2 to our Registration Statement on
     Form S-8, File No. 333-44350, filed August 23, 2000.

(18) Incorporated by reference to the correspondingly numbered exhibit to our
     Registration Statement on Form S-8, File No. 333-58955, filed July 13,
     1998.

(19) Incorporated by reference to Exhibit 10.31 to our Quarterly Report on Form
     10-Q for the quarter ended September 30, 2000, File No. 0-20815, filed
     November 14, 2000.

(20) Appendix 5 of this exhibit is incorporated by reference to Exhibit 10.17 to
     our Registration Statement on Form S-3, File No. 333-41649, filed December
     5, 1997.

(21) Incorporated by reference to the correspondingly numbered exhibit to our
     Registration Statement on Form S-3, File No. 333-41649, filed December 5,
     1997.

(22) Incorporated by reference to the correspondingly numbered exhibit to our
     Quarterly Report on Form 10-Q for the quarter ended June 30, 1998, File No.
     0-20815, filed August 14, 1998.

(23) Incorporated by reference to the correspondingly numbered exhibit to our
     Quarterly Report on Form 10-Q for the quarter ended September 30, 1998,
     File No. 0-20815, filed November 16, 1998.

(24) Incorporated by reference to the correspondingly numbered exhibit to our
     Annual Report on Form 10-K for the year ended on December 31, 1998, File
     No. 0-20815, filed March 31, 1999.

(25) Incorporated by reference to the correspondingly numbered exhibit to our
     Quarterly Report on Form 10-Q for the quarter ended March 31, 1999, File
     No. 0-20815, filed May 13, 1999.

(26) Incorporated by reference to the correspondingly numbered exhibit to our
     Quarterly Report on Form 10-Q for the quarter ended June 30, 1999, File No.
     0-20815, filed August 13, 1999.

(27) Incorporated by reference to the correspondingly numbered exhibit to our
     Quarterly Report on Form 10-Q for the quarter ended September 30, 1999,
     File No. 0-20815, filed November 15, 1999.

(28) Incorporated by reference to Exhibit 10.30 to our Quarterly Report on Form
     10-Q for the quarter ended June 30, 2000, File No. 0-20815, filed August
     11, 2000.







<PAGE>   20



(29) Incorporated by reference to Exhibit 99.3 to our Registration Statement on
     Form S-8, File No. 333-44350, filed August 23, 2000.

(30) Incorporated by reference to Exhibit 99.4 to our Registration Statement on
     Form S-8, File No. 333-44350, filed August 23, 2000.