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Notice to Readers: Supplemental Recommendations About the Timing of Influenza Vaccination, 2004--05 Season

In early August 2004, discussion with the Food and Drug Administration (FDA) and influenza vaccine manufacturers indicated that production of vaccine for the 2004--05 influenza season was proceeding satisfactorily. However, on August 26, Chiron Corporation announced that, in conducting final internal release procedures for its inactivated influenza vaccine, Fluvirin®, the company's quality-assurance systems had identified a small number of lots that did not meet product sterility specifications; these lots will not be distributed. In recent discussions with CDC, the company stated that laboratory testing determined the problem was localized. After the company completes its quality-assurance testing, all remaining lots that have met sterility specifications will be available for distribution. Chiron expects to distribute 46--48 million doses during this influenza season, with 42--44 million doses distributed in October and the remaining doses distributed in early November. Total influenza-vaccine production from all manufacturers who will supply the U.S. market during the 2004--05 influenza season is estimated at 100 million doses, which is approximately 13 million more doses than was produced for the 2003--04 influenza season.

CDC is recommending that influenza vaccination proceed for all recommended persons as soon as vaccine is available, recognizing that availability might be limited in early October. Some delay might occur for customers receiving influenza-vaccine doses purchased from Chiron, which might result in a need to reschedule planned clinics and other vaccination campaigns. The optimal time to vaccinate against influenza is October and November, and the Advisory Committee on Immunization Practices (ACIP) recommends that persons planning substantial organized vaccination campaigns consider scheduling those events after mid-October because availability of vaccine in any one location cannot be ensured consistently in early fall. Aventis Pasteur, Inc. expects to distribute approximately 52 million doses of inactivated influenza vaccine (Fluzone®) this season. MedImmune Vaccines, Inc., expects to distribute approximately 1.5 million doses of live attenuated influenza vaccine (FluMist). No delays in the timing of distribution of vaccine from these two manufacturers of influenza vaccine are expected.

The annual preseason assessment of each year's projected vaccine supply was requested by ACIP to help address vaccine shortages first experienced in 2000. The committee recommended that mass vaccination campaigns for the 2000--01 season be delayed until the availability of supply was ensured (1,2). ACIP issued similar recommendations for the 2001--02 influenza season (3) and incorporated into its annual influenza recommendations the possible use of prioritized timing of vaccine administration when necessary because of vaccine shortages or delays (4). No delays occurred in vaccination campaigns during either the 2002--03 or the 2003--04 (5) seasons.

CDC also will purchase 4.5 million doses of inactivated influenza vaccine, which will be held in a stockpile to ensure sufficient supply in the event of increased demand like that experienced last winter. CDC has legislative authority through the Vaccines for Children program to purchase influenza vaccine for a national stockpile program for children aged <18 years. Additional information about influenza and influenza vaccination is available from CDC at


  1. CDC. Delayed supply of influenza vaccine and adjunct ACIP influenza vaccine recommendations for the 2000--01 influenza season. MMWR 2000;49:619--22.
  2. CDC. Updated recommendations from the Advisory Committee on Immunization Practices in response to delays in supply of influenza vaccine for the 2000--01 season. MMWR 2000;49:888--92.
  3. CDC. Delayed influenza vaccine availability for 2001--02 season and supplemental recommendations of the Advisory Committee on Immunization Practices. MMWR 2001;50:582--5.
  4. CDC. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2004;53(No. RR-6).
  5. CDC. Supplemental recommendations about the timing of influenza vaccination, 2003--04 season. MMWR 2003;52:796--7.

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