Large Recall of Children's Swine Flu Vaccine

Dec. 16 -- TUESDAY, Dec. 15 (HealthDay News) -- Almost 800,000 children's doses of H1N1 swine flu vaccine have been recalled by manufacturer Sanofi Pasteur Inc. because they have lost some potency, federal health officials said Tuesday.

According to the U.S. Centers for Disease Control and Prevention, the company's routine testing of the vaccine for children aged 6 months to almost 3 years found that four batches had lower than required potency levels.

"This means that doses from these four vaccine lots no longer meet the manufacturer's specifications for potency," according to the CDC.

Since the potency of the recalled vaccine is only "slightly" below the required range of potency, children who have received vaccine from these lots do not need to be revaccinated, the agency said.

"This is not a safety problem; it's an issue of efficacy," said infectious disease expert Dr. Marc Siegel, an associate professor of medicine at New York University, in New York City.

Siegel said this recall is good news because it means the vaccine is being tested after it is shipped. "I am happy to see them testing this, because one of the things that happens is once a vaccine gets to market it kind of gets forgotten," he said.

Specifically, the recalled doses are in single shot pre-filled syringes, and do not contain the preservative thimerosal. To be protected from swine flu, children under 10 need two shots spaced about a month apart.

"I don't think this is a coincidence that this is occurring in the single-dose syringes," Siegel said. "This process is very labor-intensive. The more intensive the process, the more likely we will see variation in efficacy."

Although the manufacturer is asking that unused doses be returned, the vaccine itself is safe. "There are no safety concerns with these lots of H1N1 vaccine. All lots successfully passed pre-release testing for purity, potency and safety," the CDC said.

Siegel agreed that the small drop in potency is not enough to require another vaccination. "The children that received this vaccine are very likely to have a significant amount of immunity, because the immune response as tested in studies was profound," he said.