The Sanofi vaccine is a killed vaccine. Live vaccines may be killed by adverse environmental conditions, and protein in a killed vaccine may be denatured by heating or freezing. But the vaccine was only just manufactured, and should not have lost potency naturally in the short time since it left the plant. Likely it never met potency requirements. Why would vaccine be retested weeks after passing a potency test? Perhaps the potency tests weren't conducted before the 4 lots were released, given the hurry for vaccine.
The recall is for about 800,000 pre-filled syringes intended for young children, ages 6 months to nearly 3 years. The shots, made by Sanofi Pasteur, were distributed across the country last month and most have already been used, according to the Centers for Disease Control and Prevention.
Doctors were notified of the voluntary recall on Tuesday. Dr. Anne Schuchat, a CDC flu expert, stressed that parents don't need to do anything or to worry. The vaccine is still safe, she said.
The issue is the vaccine's strength. Tests done 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. Why the potency dropped isn't clear.
Yet the FDA says, "In addition, before they can be used, all Influenza A (H1N1) 2009 monovalent vaccines must undergo the same rigorous FDA manufacturing oversight, product quality testing and lot release procedures that apply to seasonal influenza vaccines." And the FDA Commissioner repeated this in a November 10 letter to health professionals:
We are not cutting any corners. Just as for seasonal influenza vaccine, no lot of the 2009 H1N1 vaccine can be used until it has been carefully evaluated and released as sterile and potent by both the manufacturer and by the FDA.So it's unclear what the facts are.
Children who already received most of this lot are probably not protected, although some officials are saying otherwise. They are still susceptible to adverse reactions from the vaccine components, whether or not the vaccine was effective.