Sanofi-Aventis is recalling some 800,000 pediatric doses of H1N1 vaccine because tests showed some batches weren't potent enough, the Centers for Disease Control and Prevention said. The CDC said the shots' potency was "only slightly below the 'specified' range" and that there were no safety concerns, the Wall Street Journal reports.
Apparently, the problem didn't arise in manufacturing; when the vaccines were made, they met all the guidelines for potency and safety. But when the shots were tested later, the potency had declined below the proper range.
The recalled batches were prefilled syringes designed for children six months to three years of age. Children who have already been vaccinated from the recalled lots won't have to get another shot, however, the CDC said, because the amount of antigen in the shots should still be enough to protect them from flu.