ATLANTA — Hundreds of thousands of swine flu shots for children — including some 21,800 in Kentucky — have been recalled because tests indicate that the vaccine doses lost some strength, government health officials said Tuesday.
The shots, made by Sanofi Pasteur, were distributed across the country last month, and most already have been used, according to the Centers for Disease Control and Prevention. The 800,000 pre-filled syringes that were recalled are for children ages 6 months to nearly 3 years.
Dr. Anne Schuchat, a CDC flu expert, emphasized that parents don't need to do anything or to worry if their child got one — or even two — of the recalled shots. The vaccine is safe and effective, she said.
The issue is the vaccine's strength. Tests conducted 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.
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Why the potency dropped isn't clear. "That's the $64,000 question," said Len Lavenda, a Sanofi Pasteur spokesman.
Kentucky received 21,800 doses of the vaccine, said Dr. Doug Thoroughman, the epidemiology field officer assigned to Kentucky by the CDC.
In Fayette County, 30 children who received their first dose of the vaccine at the Dec. 5 clinic at Bryan Station received vaccine from lots that are being recalled. Kevin Hall, spokesman for the Lexington-Fayette County Health Department, said parents are urged to simply make an appointment for the second vaccine.
Thoroughman said any Kentucky health department that received the recalled vaccine should have been notified Tuesday. All doses should be off the shelf within days. It probably will be up to each health department to let communities know whether it gave out the recalled vaccine.
But, he said, "There is nothing wrong with the vaccine that is going to hurt anybody."
Young children are supposed to get two doses, spaced about a month apart. Health officials say they don't think children need to get vaccinated again, even if they got both doses from the recalled lots, Schuchat said.
That's because, Thoroughman said, the antigen level in the vaccine is set intentionally high to ensure the best outcome. A slight slip does not render it ineffective, he said. Antigens help spur an immune response, setting the body up to defend against the H1N1 virus should it appear.
"The doses recalled simply didn't meet the specifications for potency levels by a small amount," Hall said. "It's like having 15 ounces of sugar in a 16-ounce packet. There's enough antigen there to protect you, but it's not quite the amount the company intended to put in the dose."
Swine flu vaccine has been available since early October and, since then, manufacturers have released about 95 million doses in the United States.
Sanofi Pasteur is the vaccines division of Sanofi-Aventis Group, based in France. All vaccines tested fine when they were shipped earlier this fall. But last week, testing of one lot showed that the potency had fallen about 12 percent below the government standard, Lavenda said.
The company found three other lots with diminished strength. It notified government health officials and conducted a voluntary recall. The vaccine has been in high demand, and the company doesn't expect to see many doses come back, Lavenda said.
Officials with the Food and Drug Administration, the CDC and the company all said they think the strength of the recalled doses is high enough to protect children against the virus. No potency problem has been detected in the same vaccine packaged in other types of syringes or vials, Lavenda said.
Experts say the problem is limited to the children's pre-filled syringes. The antigen might be sticking to the walls of those syringes, said Dr. Jesse Goodman, the FDA's deputy commissioner for science and public health.