The vaccine manufacturer MedImmune announced at the end of last year that the H1N1 vaccine had lost effectiveness since it first appeared.  Nevertheless, according to U.S. officials, this does not imply a safety issue.

The mentioned manufacturer withdrew thirteen lots of the vaccine against the H1N1 influenza out of its own free will because these had lost part of its effectiveness since they were first manufactured.

In response, Norman Baylor, the director of the Office of Vaccines Research and Review at the Food and Drug Administration, stated that this situation does not create a safety issue because every lot had passed the pre-release testing required to ensure safety, purity, and effectiveness.  He maintained that the loss of effectiveness was a slight one.

The thirteen lots that were withdrawn were a part of 4.7 million doses of the intranasal vaccine, whose origin is a live weakened virus; however, officials think that the majority of these were administered during October and November of 2009 when the vaccine was still performing at its maximum effectiveness.  At the moment of the announcement, the manufacturer still had in its possession 3000 doses affected by the withdrawal, but it is not clear how many are scattered around the country.

This is not the first time lots of the H1N1 vaccine have been withdrawn.  Some weeks after MedImmune’s incident, Sanofi-Aventis withdrew 800,000 doses of the vaccine for children for the same reason; their effectiveness had decreased.

Baylor accepted that this pattern is not normal, having two withdrawals of a seasonal flu vaccine in the same season; however, he explained that these are biologicals created from living organisms and thus, it is normal for the vaccine to lose effectiveness over time.

It is for this reason that the vaccine has an authorized shelf life of 18 weeks and that the FDA demands that companies measure its effectiveness regularly.  MedImmune tests its products on a weekly basis, and it was on one of these occasions that the loss of effectiveness was accounted for.

Baylor noted that the withdrawal was a measure of precaution.  He added that those who received vaccines from these lots are fully protected and don’t need to get another shot.  According to him, there is no negative impact whatsoever on the vaccine’s safety and effectiveness.

Contact your pharmaceutical consulting firm, because it should have a lot to say on this respect and lots of important recommendations.

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