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Almost five million doses of a nasal swine flu vaccine have been recalled by drug maker MedImmune – as the treatment appears to lose strength over time, health officials in the US have announced.
This is the second vaccine to be recalled in December over problems with diminishing potency.
The move comes as public health officials urge millions of Americans to get vaccinated against the virus.
MedImmune’s recall 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 is 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.
Last week, vaccine maker Sanofi Pasteur recalled hundreds of thousands of swine flu shots for children because tests indicated those doses lost some strength. Most of those doses had also already been used.
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