Millions of H1N1 Vaccine Doses Recalled Due to Potency Problem

Nearly five million doses of an H1N1 swine flu vaccine were recalled today because the strength of the nasal sprays may have decreased over time and they may not be as potent as they are supposed to be, the Food and Drug Administration said.

Only about 3,000 of the recalled vaccine doses produced by the MedImmune unit of drug maker AstraZeneca are believed to still be in circulation or storage. The vast majority were administered to patients in October and November, at the peak of the H1N1 vaccination process, according to a Reuters news report.

At that time, health officials say the doses were still at their appropriate potency. The FDA is therefore not recommending people who received the vaccinations back in October or November to get another dose.

This is not the first time a pharmaceutical company has had to recall H1N1 vaccines due to concerns about reduced potency. Just last week, French vaccine maker Sanofi-Aventis recalled about 800,000 doses of its pediatric H1N1 swine flu vaccine because it was not as potent as it should be.

Specific Lots Targeted

The recall of the MedImmune vaccine involves unused doses from 13 specific lots of nasal spray vaccine. Routine checking of the potency of vaccines being held in storage found the doses had lost some of their potency. The company is recommending that doses from all lots marked with expiration dates between Jan. 19 and Jan. 26, 2010 not be used.

Officials said they are investigating the reason behind the drop in potency of the stored vaccine doses.

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