WASHINGTON — Drugmaker MedImmune is recalling nearly 5 million doses of H1N1 flu vaccine because the nasal spray appears to lose strength over time, federal health officials announced Tuesday.
The vaccine recall is the second this month caused by declining potency and comes as public health officials urge millions of Americans to get vaccinated against swine flu.
The action affects more than 4.6 million doses, but the vast majority have already been used, according to the Food and Drug Administration. Agency officials said the vaccine was strong enough when it was distributed in October and November.
"The slight decrease in potency is not expected to have any effect on the protective effect of the vaccine," said Norman Baylor, director of the FDA's vaccine research office. "We are not recommending revaccination."
The agency is looking into the problem but said it's not uncommon for vaccines to lose strength over time. MedImmune's vaccine has a recommended shelf life of about four months. The company has about 3,000 doses in its warehouses but does not know how many remain in the field, according to the FDA