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Seasonal Influenza Vaccine Supply and Distribution in the United States

Questions & Answers

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Supply

With more manufacturers producing influenza vaccine for the US, can we still anticipate experiencing disruptions to the influenza vaccine supply?

The challenges associated with the U.S. influenza vaccine supply are multi-faceted. Influenza viruses change from year to year, so influenza vaccines must be updated annually to include the viruses that will most likely circulate in the upcoming season. Once the viruses are selected for the new formulation, manufacturers operate under a very tight timeline for producing, testing, releasing and distributing the vaccine. Due to these time constraints, any problems encountered during production may cause shortages or delays, and in fact, such problems have impacted the supply in prior influenza seasons.

Has CDC created an influenza vaccine stockpile to address vaccine supply disruptions?

Beginning in 2004, CDC began purchasing a late-season influenza vaccine stockpile to provide a limited quantity of vaccine for children (using Vaccines for Children [VFC] Program funds) to address urgent supply problems that may exist in December, January or beyond. Since in most years, influenza disease activity does not peak until January or later, this approach to stockpiling can be quite useful if vaccine production delays or shortages drive demand later in influenza vaccination season.

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Why is vaccine always left at the end of each annual vaccination campaign?

Demand for influenza vaccine varies from year to year. Within each influenza vaccination season, demand varies by month, usually peaking in October or November and rapidly declining after that. Meanwhile, because timing of influenza vaccine production and distribution is unpredictable, availability of the vaccine supply does not always coincide with peak demand. Thus, manufacturers with vaccine coming off the production line in middle or late November or later may not be able to sell it all and providers receiving vaccine in this same time frame may not be able to convince patients to receive it, even though late season vaccination is encouraged and in most years will be beneficial.

Are manufacturers still working to remove thimerosal from influenza vaccines?

Yes, efforts are ongoing to increase the supply of thimerosal-free or preservative-free (trace thimerosal) influenza vaccine for the U.S. market. At the present time, six of seven manufacturers licensed in the United States produce at least one formulation that is thimerosal-free or preservative-free (trace thimerosal). See the Table: Influenza Vaccine Manufacturers for the 2013-14 Influenza Season.

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Distribution

Why can't CDC control the distribution of influenza vaccine so that providers seeing priority patients receive their orders first?

Influenza vaccine production and distribution in the US are primarily private sector endeavors. CDC does not have the authority, resources or relationships with providers necessary to carry out or control vaccine distribution.

CDC encourages influenza vaccine manufacturers and distributors to use a distribution strategy that provides vaccine to all provider types in a comparable timeframe. Such an approach allows the broadest possible access for vaccine throughout the season and is consistent with national data that indicate adults in the United States receive influenza vaccine in a wide variety of venues, including private provider offices, worksites, clinics, hospitals, health departments, retail settings, and senior centers. While there is a relationship between age or health status and the location in which vaccines are received, the data demonstrate that all of these venues serve at least some elderly or high risk patients.

It seems that my vaccines come in multiple shipments during the season, which makes planning difficult. Why can't vaccine be ready and delivered prior to the beginning of the vaccination season?

The timing of the completion of influenza vaccine production varies from year to year and depends upon on a number of factors, including the strains chosen for inclusion in the vaccine. Even in a year in which each step of production goes well, since influenza vaccine manufacturers are currently producing vaccine at or near full capacity, it isn't possible for all of the doses to be produced and distributed before the beginning of the vaccination season.

To allow as many providers as possible to begin vaccinating early in the season, CDC encourages manufacturers and distributors to use a distribution strategy in which partial shipments are used to allow as many providers as possible to begin vaccination activities early in the vaccination season. Ideally, the intervals between shipments are short so that each provider has a continuous supply and can continue vaccinating patients without interruption.

Why can't influenza vaccine manufacturers and distributors always provide reliable information about when vaccine shipments are scheduled?

Manufacturers say that, because of the unpredictable nature and complexity of biologics production, they cannot always anticipate when vaccine lots will be completed and released. Distributors must rely on the manufacturers to provide them with this information. Both manufacturers and distributors are reluctant to project very far into the future about when shipments will be made because they do not want to create unrealistic expectations among customers.

Why is there so much variation in when different vaccination providers receive their vaccine?

The primary reason for the variation in timing is that different types of vaccine providers receive their vaccine from different sources. A provider may order influenza vaccine (1) directly from the manufacturer; (2) from a distributor, who is a customer of the manufacturer; or (3) from a secondary distributor, from whom the provider also receives other medical products. Some of these routes of distribution are more direct than others, which can affect the timing of vaccine delivery.

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