800,000 Kids' H1N1 Flu Shots Recalled

Last updated 12:30 p.m. Eastern

Hundreds of thousands of H1N1 (swine) flu shots for children have been recalled because tests indicate the vaccine doses lost some strength, government health officials said Tuesday.

The recall is for about 800,000 pre-filled syringes intended for young children, ages 6 months to nearly 3 years. The shots, made by Sanofi Pasteur, were distributed across the country last month and most have already been used, according to the Centers for Disease Control and Prevention.

Doctors were notified of the voluntary recall on Tuesday. Dr. Anne Schuchat, a CDC flu expert, stressed that parents don't need to do anything or to worry. The vaccine is still safe, she said.

CBSNews.com Special Report: H1N1 Virus
Dr. Ashton: What Kids Know about H1N1

The issue is the vaccine's strength. Tests done before the shots were shipped showed that the vaccines were strong enough. But tests done weeks later indicated the strength had fallen slightly below required levels. Why the potency dropped isn't clear.

Children in that age group are supposed to get two doses, spaced about a month apart. Health officials don't think children need to get vaccinated again, even if they got two doses from the same lots, said Schuchat.

H1N1 flu vaccine has been available since early October, and since then manufacturers have released about 95 million doses for distribution in the United States.

The recalled shots were made by Sanofi Pasteur, the vaccines division of France-based Sanofi-Aventis Group. The company reported the potency findings to the government officials and did a voluntary recall.

Sanofi Pasteur bills itself as the No. 1 manufacturer of flu vaccines in the world. It makes flu vaccine at sites in France and in Pennsylvania.

Sanofi Pasteur is recalling four lots of pediatric Influenza A (H1N1) 2009 Monovalent Vaccine because routine testing measured lower antigen content than the specification limit. These lots passed all quality controls and met all specifications required by government agencies at the time of shipping. There are no safety concerns related to this action.

These lots of vaccine were manufactured by Sanofi Pasteur and administered to infants 6 through 35 months of age for protection against the 2009 pandemic influenza A (H1N1) virus. The affected vaccine is identified by the following lot numbers:

UT023DA
UT028DA
UT028CB
UT030CA

The vaccine was first shipped on September 29, 2009.

The U.S. Food and Drug Administration (FDA) and the U.S. Centers for Disease Control and Prevention (CDC) have evaluated the data and are confident that the health of children immunized with this product has not been compromised. Moreover, persons immunized with these lots do not need re-immunization.

No action is needed other than to return unused doses. The FDC and the CDC recommend NOT repeating the dose for children who received vaccine from these lots because the drop in antigen content is unlikely to result in a clinically significant reduction in immune response. The CDC has stated that parents of children who received vaccine from the recalled lots do not need to take any action other than to complete the two-dose immunization series if not already completed.

Taken together, the results of the potency testing and analyses from the literature support the conclusion that the minor decrease of antigen content of the monovalent H1N1 2009 vaccine will have no material clinical impact on protection of children 6 through 35 months of age.

Sanofi Pasteur is working closely with the FDA and the CDC to notify those who have administered the vaccine.

Sanofi Pasteur is committed to providing its customers with vaccines of the highest purity, potency and safety. A world leader in human vaccines, Sanofi Pasteur provided more than 1.6 billion doses of vaccine in 2008, making it possible to immunize more than 500 million people across the globe.