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MedImmune recalls millions of doses of swine flu vax

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AstraZeneca's MedImmune is scrambling to retrieve up to about five million doses of swine flu vaccine that has lost at least some of its potency. FDA officials were quick to reassure the public that the doses--delivered in a nasal spray--were safe and that the people who had already received a shot drawn from the 13 lots now being recalled don't need to go back out and get a second jab.

Just a week ago Sanofi-Aventis had to issue a recall for 800,000 doses that had lost their potency. Manufacturers hold on to samples of their flu vaccine to periodically review their potency. And in this case, like others, the manufacturer doesn't expect to actually get many of the shots back. Only about 3,000 doses of the recalled lots are in the warehouse. And the FDA says that most have been administered.

A spokesperson for the FDA says that scientists are trying to determine exactly why these doses lost potency. These kinds of cases are rare. And while Sanofi's vaccine could have lost potency as the antigen clung to the wall of the syringe over time, MedImmune relies on a different applicator for its nasal spray vaccine. Health officials say that about 60 million people in the United States have now been inoculated. AZ has delivered 23 million of the 40 million doses it's sold to the U.S.

- here's the report from Bloomberg
- read the Reuters story

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More stories about vaccine potency   MedImmune   H1N1   AstraZeneca  

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to clarify: MedImmune doesn't actually rely on "a different type of applicator" than other vaccines. The [FluMist-like] vaccine is delivered from a nasal applicator that is based on a conventional pre-fillable glass barrel syringe design, very similar in materials of construction to conventional prefilled syringes. This may or may not have contributed to lost potency.

More likely is that, in an effort to maximize the number of doses that could be produced from limited supplies of eggs and constrained manufacturing capacity, doses were blended, filled, and released near the lower release limit for the product, leaving little leeway for naturally occurring loss of potency over time down to a lower specification limit for the product. This product uses an infectivity-based cell culture assay for potency assessment for purposes of lot release and stability analysis. What the article does not mention is whether the lots in question actually tested below a specification limit or were just trending that way, and whether all lots in the recall gave this indication or just some, with the rest being recalled out of an abundance of caution.

Some clarification by the company might go a long way in preventing what could be come a public relations disaster for this product that already has a troubled marketing history.

Given the way MedImmune's vaccine works, by inducing an attenuated infection in the host, it is highly likely that significantly lower amounts of vaccine virus would still result in an equivalently protective effect. Even a loss of ten-fold potency could probably still result in a fully productive infection.

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