800,000 doses of pediatric H1N1 vaccine recalled because of potency, CDC says

WASHINGTON — Vaccine maker Sanofi Pasteur is recalling 800,000 doses of its pediatric H1N1 swine flu vaccine because it is not as potent as it should be, U.S. officials said Dec. 15.

There is no safety concern and children already vaccinated from the lots will not need to be revaccinated, the U.S. Centers for Disease Control and Prevention said.

The affected vaccines are four lots of pre-filled syringes for children under age 3, the CDC said in a message to state and local health officers, public information officers and doctors' groups. A CDC spokesman said about 800,000 doses of vaccine from the lots had been distributed to providers.

The CDC said the four lots were discovered as part of a testing program and that the company had also notified the U.S. Food and Drug Administration.

Stability testing means measuring the potency of a vaccine over time, according to the CDC. Tests are performed because sometimes the strength of a vaccine can go down over time.

On Dec. 7, Sanofi Pasteur notified CDC and FDA that the potency in one lot of pediatric syringes that had been distributed was later found to have dropped below a pre-specified limit. As a result, Sanofi Pasteur tested additional lots and found that three others that had been distributed also had an antigen content that, while properly filled at the time of manufacturing, was later measured to be below pre-specified limits.

This means that doses from these four vaccine lots no longer meet the manufacturer’s specifications for potency.

The CDC did not have specific destinations for the lots, which were distributed in November.

"While the antigen content of these lots is now below the specification limit for the product, CDC and FDA are in agreement that the small decrease in antigen content is unlikely to result in a clinically significant reduction in immune response among persons who have received the vaccine," the CDC said.

"For children 6 months of age and older, vaccine is available in multidose vials. The vaccine in multidose vials is safe and effective vaccine for children," it added.

The CDC says the vaccine potency is only slightly below the “specified” range. The vaccine in these lots is still expected to be effective in stimulating a protective response despite this slight reduction in the concentration of antigen. There is no need to re-administer a dose to those who received vaccine from these lots.

However, as is recommended for all 2009 H1N1 vaccines, all children younger than 10 years old should get the recommended two doses of H1N1 vaccine approximately a month apart for the optimal immune response. Therefore, children younger than 10 years old who have only received one dose of vaccine thus far should still receive a second dose of 2009 H1N1 vaccine.