Warning letters went out to thousands of doctors today alerting them that Sanofi Aventis is recalling 800,000 doses of pediatric swine flu vaccine in prefilled syringes because routine tests disclosed that its potency has diminished, officials say.
Despite the recall, the vaccine is safe and effective; parents need not worry about unusual side effects or having their children re-vaccinated, says Anne Schuchat, director of the Centers for Disease Control and Prevention's Center for Immunization and Respiratory Diseases. "There's no need for parents to call pediatricians. We think the doses given are protective and safe," she says.
Routine tests show that the active ingredient decreased by about 12%, Sanofi officials say, noting that just 50% of the antigen in a vaccine dose still appears to generate protective immunity.
The voluntary recall represents the latest hurdle in the government's drive to supply enough vaccine to protect more than 159 million Americans in five risk groups from the H1N1 virus. Those groups are pregnant women, household contacts of babies younger than 6 months, health workers, children and young people ages 6 months to 24 years, and adults 25 to 64 with chronic illnesses.
Since October, five vaccine manufacturers, including Sanofi, have churned out nearly 95 million doses, enough that more than half of the states and many local health departments have offered vaccine to anyone who wants it, Schuchat says.
Children 6 months to 9 years old should get two doses about a month apart, the CDC says.
The weakened vaccine, packaged in half-dose amounts meant for children 6 months to nearly 3 years old, represents about 1% of the nation's H1N1 vaccine supply. It makes up 18% of the 4.5 million doses in prefilled syringes made by Sanofi for children in that age group, says company spokesman Len Lavenda.
The vaccine was fine when it was shipped, but its potency apparently faded during a month of storage, Schuchat says. She adds that many of the doses may have been given while the vaccine's effectiveness was at its peak.
Injectable vaccine is licensed to be stable for 18 months; the nasal spray should last for 18 weeks. Seasonal flu vaccine is typically dated to expire in June of the year after it was produced. "Month to month" its potency may drop, but usually not enough to limit its effectiveness, Schuchat says.
Lavenda says Sanofi officials are baffled at the vaccine's loss of muscle. "It's a mystery," he says. "We can't remember a time when flu vaccine lost potency."
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