<PAGE>


                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                    FORM 8-K


                                 CURRENT REPORT

                     PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934
                        Date of Report: December 20, 1999



                                 MEDIMMUNE, INC.
             (Exact name of registrant as specified in its charter)



                         Commission File Number: 0-19131




                     Delaware                          52-1555759
             (State of Incorporation)              (I.R.S. Employer
                                                   Identification No.)



                35 West Watkins Mill Road, Gaithersburg, MD 20878
                (Address of principal executive office (Zip Code)


Registrant's telephone number, including area code (301) 417-0770


No Exhibits are being filed with this report.


CytoGam, RespiGam and Synagis are registered trademarks of the Company.





<PAGE>



MEDIMMUNE, INC.
Current Report on Form 8-K

ITEM 5.  OTHER EVENTS

MedImmune,  Inc.  reported  the  information  contained in the  following  press
release dated December 17, 1999:



             MEDIMMUNE ANNOUNCES LICENSURE OF MANUFACTURING FACILITY

     Gaithersburg,  MD, December 17, 1999 - MedImmune, Inc. (Nasdaq: MEDI) today
announced the approval of its new manufacturing facility in Frederick,  Maryland
by the U.S.  Food and Drug  Administration.  This approval  allows  MedImmune to
begin distributing Synagis manufactured at the facility.  Synagis  (palivizumab)
is a drug used to prevent  serious lower  respiratory  tract  disease  caused by
respiratory  syncytial  virus  (RSV) in  pediatric  patients at high risk of RSV
disease  (see  full  prescribing  information  at  www.medimmune.com/  products/
synagispi.htm).  This  facility  will augment the supply of Synagis  produced at
Boehringer  Ingelheim  Pharma KG in  Biberach,  Germany,  under  their  contract
manufacturing agreement with MedImmune.

Dr.  Wayne T.  Hockmeyer,  MedImmune's  chief  executive  officer and  chairman,
stated: "Since MedImmune's inception, our goal has been to be a fully integrated
company,  capable  of  taking a  product  from  discovery  through  development,
marketing and sales.  The  licensure of this plant is an important  step in this
process  and further  establishes  us as a solid  presence in the  biotechnology
industry.  Many factors  contributed to achieving this milestone,  including the
dedication and hard work of our employees, as well as the ongoing support of the
state of  Maryland  and the city and  county  of  Frederick.  We thank all those
involved  throughout  the process and look  forward to this  manufacturing  site
contributing  meaningfully to the growth of MedImmune and the community of which
it is a part."

The Frederick manufacturing facility was structurally completed in January 1998.
It is located  on a 26-acre  site  approximately  30  minutes  from  MedImmune's
headquarters  in  Gaithersburg,  Maryland.  With a floor space of  approximately
90,000  square  feet,   the  facility   includes   modules  for   production  of
antibody-based products as well as facilities for quality control,  warehousing,
and manufacturing administration.

Synagis is a humanized  monoclonal  antibody  used in the  prevention of serious
lower respiratory tract disease caused by RSV in pediatric patients at high risk
of RSV disease,  the most common cause of pneumonia and bronchiolitis in infants
and children.  Synagis is the first  monoclonal  antibody to be licensed for any
infectious disease. It is administered by intramuscular injection once per month
during anticipated periods of RSV prevalence,  which typically runs from October
through April in the United States, where there are over 300,000 infants at risk
of contracting  the disease.  In the United States,  MedImmune  co-promotes  the
product  with the Ross  Products  Division  of Abbott  Laboratories  (NYSE:ABT).
Outside the U.S., Abbott International distributes the product.

MedImmune,   Inc.  is  a  fully  integrated  biotechnology  company  focused  on
developing  and marketing  products that address  medical needs in areas such as
infectious disease,  transplantation medicine,  autoimmune disorders and cancer.
Headquartered in Gaithersburg,  Maryland, MedImmune has manufacturing facilities
in Frederick, Maryland and Nijmegen, The Netherlands, and an oncology subsidiary
in West Conshohocken, Pennsylvania.

<PAGE>

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 the
company's filings with the U.S.  Securities and Exchange  Commission.  MedImmune
cautions that RSV disease occurs primarily during the winter months; the company
believes its operating results will continue to reflect that seasonality for the
foreseeable future.




                                 MEDIMMUNE, INC.
                               ----------------
                               (Registrant)



Date: December 20, 1999   By: /s/David M. Mott
                              ----------------
                              David M. Mott, Vice Chairman and
                             Chief Financial Officer
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SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                    FORM 8-K

                                 CURRENT REPORT

                     PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934
                        Date of Report: December 20, 1999

                                 MEDIMMUNE, INC.
             (Exact name of registrant as specified in its charter)

                         Commission File Number: 0-19131

                     Delaware                          52-1555759
             (State of Incorporation)              (I.R.S. Employer
                                                   Identification No.)

                35 West Watkins Mill Road, Gaithersburg, MD 20878
                (Address of principal executive office (Zip Code)

Registrant's telephone number, including area code (301) 417-0770

No Exhibits are being filed with this report.

CytoGam, RespiGam and Synagis are registered trademarks of the Company.
MEDIMMUNE, INC.
Current Report on Form 8-K

ITEM 5.  OTHER EVENTS

MedImmune,  Inc.  reported  the  information  contained in the  following  press
release dated December 17, 1999:

             MEDIMMUNE ANNOUNCES LICENSURE OF MANUFACTURING FACILITY

     Gaithersburg,  MD, December 17, 1999 - MedImmune, Inc. (Nasdaq: MEDI) today
announced the approval of its new manufacturing facility in Frederick,  Maryland
by the U.S.  Food and Drug  Administration.  This approval  allows  MedImmune to
begin distributing Synagis manufactured at the facility.  Synagis  (palivizumab)
is a drug used to prevent  serious lower  respiratory  tract  disease  caused by
respiratory  syncytial  virus  (RSV) in  pediatric  patients at high risk of RSV
disease  (see  full  prescribing  information  at  www.medimmune.com/  products/
synagispi.htm).  This  facility  will augment the supply of Synagis  produced at
Boehringer  Ingelheim  Pharma KG in  Biberach,  Germany,  under  their  contract
manufacturing agreement with MedImmune.

Dr.  Wayne T.  Hockmeyer,  MedImmune's  chief  executive  officer and  chairman,
stated: "Since MedImmune's inception, our goal has been to be a fully integrated
company,  capable  of  taking a  product  from  discovery  through  development,
marketing and sales.  The  licensure of this plant is an important  step in this
process  and further  establishes  us as a solid  presence in the  biotechnology
industry.  Many factors  contributed to achieving this milestone,  including the
dedication and hard work of our employees, as well as the ongoing support of the
state of  Maryland  and the city and  county  of  Frederick.  We thank all those
involved  throughout  the process and look  forward to this  manufacturing  site
contributing  meaningfully to the growth of MedImmune and the community of which
it is a part."

The Frederick manufacturing facility was structurally completed in January 1998.
It is located  on a 26-acre  site  approximately  30  minutes  from  MedImmune's
headquarters  in  Gaithersburg,  Maryland.  With a floor space of  approximately
90,000  square  feet,   the  facility   includes   modules  for   production  of
antibody-based products as well as facilities for quality control,  warehousing,
and manufacturing administration.

Synagis is a humanized  monoclonal  antibody  used in the  prevention of serious
lower respiratory tract disease caused by RSV in pediatric patients at high risk
of RSV disease,  the most common cause of pneumonia and bronchiolitis in infants
and children.  Synagis is the first  monoclonal  antibody to be licensed for any
infectious disease. It is administered by intramuscular injection once per month
during anticipated periods of RSV prevalence,  which typically runs from October
through April in the United States, where there are over 300,000 infants at risk
of contracting  the disease.  In the United States,  MedImmune  co-promotes  the
product  with the Ross  Products  Division  of Abbott  Laboratories  (NYSE:ABT).
Outside the U.S., Abbott International distributes the product.

MedImmune,   Inc.  is  a  fully  integrated  biotechnology  company  focused  on
developing  and marketing  products that address  medical needs in areas such as
infectious disease,  transplantation medicine,  autoimmune disorders and cancer.
Headquartered in Gaithersburg,  Maryland, MedImmune has manufacturing facilities
in Frederick, Maryland and Nijmegen, The Netherlands, and an oncology subsidiary
in West Conshohocken, Pennsylvania.
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 the
company's filings with the U.S.  Securities and Exchange  Commission.  MedImmune
cautions that RSV disease occurs primarily during the winter months; the company
believes its operating results will continue to reflect that seasonality for the
foreseeable future.

                                 MEDIMMUNE, INC.
                               ----------------
                               (Registrant)

Date: December 20, 1999   By: /s/David M. Mott
                              ----------------
                              David M. Mott, Vice Chairman and
                             Chief Financial Officer