How the Delayed Distribution of Influenza Vaccine Created Shortages in 2000 and 2001

INTRODUCTION During the past decade, substantial increases in the production and distribution of influenza vaccine have been critical for improving vaccination coverage among groups specifically targeted for vaccination, as well as among healthy persons in the U.S.1 The increases have been critical because annual vaccination is the cornerstone of efforts to reduce the health burden from influenza, a respiratory infection resulting in an average of approximately 20,000 deaths and 114,000 hospitalizations per year in the U.S.2,3,4 The vaccine used in the U.S. contains three inactivated (killed) influenza virus strains, antigenically similar to contemporary circulating virus strains. Three manufacturers (Aventis Pasteur, Evans Vaccines, Ltd., and Wyeth Lederle Laboratories) currently distribute influenza vaccine in the U.S. Vaccine from Aventis and Wyeth is approved for use in persons six months of age and older, whereas vaccine from Evans is approved for use in persons four years and older, because efficacy data for use in younger children have not been submitted to the Food and Drug Administration (FDA). In most years, vaccine typically has been available to practitioners and other vaccine providers by October and November, the optimal months for vaccination against influenza in the U.S. In 2000 and 2001, however, the availability of influenza vaccine was significantly lower during those months than in previous years, which left many clinicians and patients unable to find vaccine and led to the cancellation of many vaccination campaigns.5,6 Ironically, in both years, increasing supplies of vaccine became available in December, but the waning levels of demand resulted in substantial surpluses of unused vaccine. The difficulties and complications associated with the production and distribution of influenza vaccine make it unique among current vaccines. Two of the primary reasons for this situation are the need to update influenza vaccines annually, so the vaccine strains remain antigenically similar to the viruses in circulation, and the need to complete all manufacturing, regulatory, and distribution steps within very short time frames, so that sufficient vaccine supplies are available to providers in time for winter influenza epidemics. In this article, we briefly review the recent influenza vaccine distribution delays, key points about the influenza vaccine production and distribution processes, and steps that should be considered to strengthen the influenza vaccine supply system.