BETHESDA, MD 15 December 2009—The Centers for Disease Control and Prevention (CDC) today announced that Sanofi Pasteur Inc. is recalling four lots of H1N1 influenza vaccine in prefilled syringes because doses from those lots—UT023DA, UT028DA, UT028CB, and UT030CA— do not meet the specification regarding the required minimum amount of antigen.

CDC, via a "health update" e-mail, said the agency and FDA agree that the "small decrease" in antigen content since release of the lots is "unlikely to result in a clinically significant reduction in immune response" in the people who received a dose. Therefore, CDC said, these vaccinees do not need revaccination.

All prefilled syringes in those lots were shipped in November, the agency said.

Sanofi Pasteur produces the vaccine in prefilled syringes for two populations: children ages 6–35 months and people age 36 months or older. Only the syringes containing 0.25 mL of vaccine, intended for children ages 6–35 months, are subject to the recall.

CDC said the company will send vaccine providers directions for returning unused syringes from the four lots.

The agency also said that the company has stopped distributing the smaller-volume prefilled syringes.

Sanofi Pasteur's multidose vials of H1N1 influenza vaccine and prefilled syringes containing 0.5 mL of vaccine continue to meet specifications, CDC said.