GlaxoSmithKline is recalling a popular four-in-one flu vaccine distributed throughout the U.S. because its effectiveness can decline over time.
The company alerted customers Tuesday that the vaccine can lose potency and fail to adequately protect against some flu strains. The Flulaval Quadrivalent Thimerosal-free vaccine in prefilled syringes is designed to protect against four strains of influenza virus. But Glaxo said it "cannot rule out potential suboptimal protection" in people who received the vaccine in early January or later.
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The recall affects about 1.7 million doses, but a company spokeswoman says it's unclear how many remain on the market. More than 99 percent of the vaccines were distributed in 2014, before the product began losing potency, according to GlaxoSmithKline's Anna Padula.
Health authorities generally recommend getting vaccinated in the fall.