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.