================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                             ----------------------

                                 SCHEDULE 14D-9
                                 (RULE 14d-101)

                   SOLICITATION/RECOMMENDATION STATEMENT UNDER
             SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934

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

                                     AVIRON
                            (NAME OF SUBJECT COMPANY)

                                     AVIRON
                      (NAME OF PERSON(S) FILING STATEMENT)
                             ----------------------

                    COMMON STOCK, PAR VALUE $0.001 PER SHARE
                         (TITLE OF CLASS OF SECURITIES)
                             ----------------------

                                   0537 62100
                      (CUSIP NUMBER OF CLASS OF SECURITIES)
                             ----------------------


                                 C. BOYD CLARKE
                 PRESIDENT, CHIEF EXECUTIVE OFFICER AND CHAIRMAN
                                     AVIRON
                           297 NORTH BERNARDO AVENUE
                         MOUNTAIN VIEW, CALIFORNIA 94043
                                 (415) 919-6500

   (NAME, ADDRESS AND TELEPHONE NUMBER OF PERSON AUTHORIZED TO RECEIVE NOTICE
                                AND COMMUNICATION
                  ON BEHALF OF THE PERSON(S) FILING STATEMENT)

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

                                WITH A COPIES TO:

ALAN C. MENDELSON, ESQ.                                FERDRICK W. KANNER, ESQ.
 PETER F. KERMAN, ESQ.                                  RICHARD D. PRITZ, ESQ.
135 COMMONWEALTH DRIVE                                   DEWEY BALLENTINE LLP
 MENOL PARK, CA 94025                                1301 AVENUE OF THE AMERICAS
    (650) 328-4600                                        NEW YORK, NY 10019
                                                            (212) 259-8000

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

         [X] Check the box if the filing relates solely to preliminary
         communications made before the commencement of a tender offer.

================================================================================

      MEDIMMUNE TO ACQUIRE AVIRON IN EXCHANGE OFFER VALUED AT $1.5 BILLION

   - AVIRON'S FLUMIST(TM) EXPECTED TO STRENGTHEN MEDIMMUNE'S INDUSTRY-LEADING
                       FRANCHISE IN INFECTIOUS DISEASE -

      - MEDIMMUNE PROVIDES PRELIMINARY 2002 GUIDANCE AND FIVE-YEAR GOALS -

Gaithersburg, MD and Mountain View, CA, December 3, 2001 -- MedImmune, Inc.
(Nasdaq: MEDI) and Aviron (Nasdaq: AVIR) announced today that they have entered
into a definitive merger agreement under which MedImmune will acquire Aviron
through an exchange offer and merger transaction. This transaction offers 1.075
MedImmune shares for each Aviron share. Based upon MedImmune's closing price of
$44.10 on November 30, 2001, this transaction values Aviron at $47.41 per share,
or approximately $1.5 billion, net of cash.

"Our acquisition of Aviron represents an excellent strategic fit and an
opportunity to generate substantial growth in the near and long-term," commented
David M. Mott, chief executive officer of MedImmune. "We believe that adding
FluMist to our existing lead product, Synagis(R) (palivizumab), could enable
MedImmune to join the elite group of biotechnology companies that have more than
one product with greater than $1 billion in annual sales potential. Aviron also
adds vaccine technology that is synergistic with our established platform in
infectious disease and immunology. Given our strengths in research and
development, manufacturing and regulatory affairs, we are well suited to analyze
the FluMist opportunity and enhance Aviron's current efforts to gain final
regulatory approval for the product. Our objective, consistent with Aviron's
previously stated goal, is to launch FluMist in 2002, which would diversify and
expand our revenue base and have the potential to significantly accelerate our
revenue and earnings growth rates from 2003 through 2006."

C. Boyd Clarke, chief executive officer and chairman of Aviron, said, "The
combination of MedImmune and Aviron creates a premier biotech company with the
potential to significantly enhance shareholder value for both companies - beyond
what either could achieve on its own. MedImmune has the skills, experience and
resources to help us ensure that the commercial potential of FluMist and our
other vaccine candidates is maximized. At the same time, our shareholders will
have the opportunity to benefit from the continued growth and success of
MedImmune's currently marketed products and strong pipeline. Our board has
concluded that this transaction is in the best interest of shareholders."

Pursuant to a 1999 agreement, Wyeth-Lederle Vaccines, a division of American
Home Products, would co-promote FluMist in the U.S. with Aviron, and would be
responsible for distributing the product throughout most of the rest of the
world. Aviron is responsible for worldwide manufacturing of the first generation
frozen FluMist product, and the companies have shared responsibility for
manufacturing the second generation liquid FluMist product. Wyeth will record
all sales of the product to end-users and Aviron will record manufacturing
revenues, milestones and royalties on Wyeth's sales. MedImmune estimates that
its revenues and operating income from FluMist will approximate half of the
worldwide end-user sales of the product and half of the overall profitability
from the product.

Aviron is a leader in the development of live, attenuated vaccines and, in
addition to FluMist, has vaccines for prevention of Epstein-Barr virus,
parainfluenza type 3, and cytomegalovirus in clinical development. Earlier stage
research programs include vaccines for respiratory syncytial virus and herpes
simplex virus.

Under the terms of the agreement, a subsidiary of MedImmune will commence an
offer to exchange 1.075 shares of MedImmune common stock for each outstanding
Aviron share. The exchange ratio is not subject to a collar. The exchange offer
will be followed by a merger to complete the transaction for the same price for
all shares not tendered through the exchange offer. The exchange offer will be
subject to customary closing conditions, including that at least a majority of
Aviron's diluted shares have been tendered, antitrust clearance obtained, and no
material adverse change to Aviron. The transaction is expected to be tax free to
Aviron shareholders. The transaction is anticipated to close in the first
quarter of 2002. The acquisition is expected to be dilutive in 2002, neutral in
2003 and significantly accretive thereafter to cash earnings before amortization
of acquisition intangibles and deal costs.

Mr. Mott added, "Aviron's employees and management have done a tremendous job in
building the value and capabilities of the company. We look forward to welcoming
the Aviron team to MedImmune and working together to build the most successful
company in the biotech industry."

ABOUT FLUMIST

FluMist is a live, attenuated virus vaccine delivered as a nasal mist for the
prevention of influenza, which was submitted to the U.S. Food and Drug
Administration for approval on October 31, 2000. Aviron received a Complete
Response Letter from the FDA on August 31, 2001. Aviron expects to file a
response to this letter by December 31, 2001 and is working to achieve approval
of the product for the 2002 flu season. Approximately 75 million influenza
vaccine doses were believed to have been manufactured for use in the U.S. for
the 2000/2001 influenza season. Given FluMist's ease of administration,
MedImmune believes this already large market has the potential to grow
substantially, primarily through expansion in the pediatric and adolescent
markets. MedImmune has established end-user sales goals for FluMist of $500
million within three years of launch and $1 billion within five years of launch.

MEDIMMUNE'S 2002 PRELIMINARY FINANCIAL GUIDANCE AND LONG-TERM GOALS

MedImmune is providing the following forward-looking information as a
convenience to investors. The guidance and objectives assume the acquisition of
Aviron closes in first quarter 2002. They also assume both the continued growth
and success of MedImmune's existing business (primarily including sales of
Synagis, Ethyol(R) (amifostine) and CytoGam(R) (cytomegalovirus immune globulin
intravenous (human)) and the successful launch of FluMist in the U.S. in
third-quarter 2002. The guidance and objectives are based upon numerous
assumptions, many of which MedImmune cannot control and which may not develop as
MedImmune expects. Consequently, actual results may differ materially from the
guidance and objectives described herein. Please refer to the Disclosure Notice
below. MedImmune expects to provide updated guidance following the closing of
the acquisition and completion of purchase accounting adjustments. Guidance and
objectives provided below refer to cash earnings per share which exclude the
impact of any in-process R&D writeoffs, amortization of intangibles and other
purchase accounting related items, which have yet to be finalized.

FOR THE YEAR ENDING DECEMBER 31, 2002:

Total revenues are projected to reach approximately $900 million and cash
earnings per share, excluding transaction related expenses, are expected to be
$0.65 to $0.70.

LONG-TERM GOALS

2003 revenues are expected to reach $1.1 billion to $1.25 billion and cash
earnings per share are expected to be $1.15 to $1.20. From 2003 - 2006,
MedImmune's goal is to achieve compound annual growth in revenues in excess of
25 percent and annual growth in earnings per share of over 30 percent.
Achievement of these goals will result in 2006 revenues in excess of $2.1
billion and cash earnings per share in excess of $2.50.

WEBCAST

MedImmune is offering a live webcast of a discussion by MedImmune and Aviron
management members regarding this merger today (December 3, 2001) at 9:00 a.m.
EST. The webcast may be accessed on MedImmune's website at www.medimmune.com. A
replay of the webcast will also be available via our website until midnight
December 10, 2001. An audio replay of the webcast will be available beginning at
11 a.m. EST on December 3, 2001 until midnight December 10, 2001 by calling
(719) 457-0820. The passcode for the audio replay is 459628.

ABOUT AVIRON

Aviron is a biopharmaceutical company headquartered in Mountain View,
California, focused on prevention of disease through innovative vaccine
technologies. The company's product portfolio includes: FluMist(TM), a live
virus vaccine delivered as a nasal mist for the prevention of influenza; a live
parainfluenza virus type 3 vaccine; a vaccine to prevent Epstein-Barr virus, and
a cytomegalovirus vaccine. For more information on Aviron, visit the company's
website at www.aviron.com.

ABOUT MEDIMMUNE

MedImmune, Inc. is a fully integrated biotechnology company focused on
developing and marketing products that address medical needs in areas such as
infectious disease, immune regulation and cancer. Headquartered in Gaithersburg,
Maryland, MedImmune has manufacturing facilities in Frederick, Maryland and
Nijmegen, the Netherlands. MedImmune markets five products, including:
Synagis(R) (palivizumab), which is marketed for the prevention of serious lower
respiratory tract disease caused by respiratory syncytial virus in pediatric
patients at high risk of RSV disease, which is prominent in the Northern
Hemisphere from October through May (see full prescribing information at
www.medimmune.com); Ethyol(R), which is marketed for the reduction of both
cumulative renal toxicity associated with repeated administration of cisplatin
in patients with advanced ovarian cancer or non-small cell lung cancer and
moderate to severe xerostomia in patients undergoing post-operative radiation
treatment for head and neck cancer, where the radiation port includes a
substantial portion of the parotid (see full prescribing information at
www.medimmune.com); and CytoGam(R), which is marketed for the prophylaxis
against cytomegalovirus disease associated with transplantation of kidney, lung,
liver, pancreas, and heart (see full prescribing information at
www.medimmune.com). MedImmune also has six products in various stages of
clinical testing for a number of diseases and a several more product candidates
in preclinical testing. For more information on MedImmune, visit the company's
website at www.medimmune.com.

DISCLOSURE NOTICE: This announcement may contain, in addition to historical
information, certain forward-looking statements that involve risks and
uncertainties. Such statements reflect management's current views and are based
on certain assumptions. Actual results could differ materially from those
currently anticipated as a result of a number of factors, including risks and
uncertainties discussed in MedImmune's and Aviron's filings with the SEC.
MedImmune and Aviron are developing products for potential future marketing.
There can be no assurance that such development efforts will succeed, that such
products will receive required regulatory clearance or that, even if such
regulatory clearance were received, such products would ultimately achieve
commercial success. There can be no assurance that the offer and merger will
close or that Aviron will be integrated successfully or without unanticipated
costs.

Aviron stockholders and other investors are urged to read the registration
statement on Form S-4, Schedule TO, preliminary prospectus, supplements, final
prospectus and other exchange offer documents which will be filed by MedImmune
with the Securities and Exchange Commission and the related
solicitation/recommendation statement which will be filed by Aviron with the
SEC. These documents will contain important information which should be

read carefully before any decision is made with respect to the offer. When
documents are filed with the SEC, they will be available for free at the SEC's
website at www.sec.gov. Documents are available for free from the contact
persons above.

IMPORTANT INFORMATION

Aviron stockholders and any potential investors in Aviron are advised to read
the tender offer statement and the solicitation/recommendation statement
regarding the acquisition, which will be filed with the Securities and Exchange
Commission upon the commencement of the tender offer. The tender offer
statement (including an offer to exchange, letter of transmittal and related
tender offer documents) and the solicitation/recommendation statement will
contain important information which should be read carefully before any
decision is made with respect to the offer. Aviron stockholders may obtain a
free copy of the tender offer statement and the solicitation/recommendation
statement when it is available and other documents filed by MedImmune and
Aviron with the SEC at the SEC's Web site at www.sec.gov. The tender offer
statement and the solicitation/recommendation statement and these other
documents may also be obtained by Aviron stockholders without cost to them from
MedImmune and Aviron.