More H1N1 Vaccine Recalled, For the Best Reason One Would Want a Vaccine Pulled Off the Shelves (But Still ...)

Another batch of H1N1 vaccine has been recalled, this time the nasal-spray version made by AstraZeneca. According to the FDA, 4.7 million doses of MedImmune were recalled yesterday. Last week, the vaccine made headlines when it was revealed that 800,000 vials of the children's vaccine, made by Sanofi-Aventis SA, were also being recalled. Luckily, neither company's products are being recalled due to any serious safety concerns─in fact, the only safety concern is that the vaccine might not protect against H1N1. However, it does present a troubling problem that health officials will need to address sooner rather than later.

In both cases, the vaccine was recalled due to the lower-than-usual potency of the doses. H1N1 vaccines are made with the H1N1 virus, to which the body reacts and produced antibodies. In the case of the pediatric vaccine, the virus was de-activated. The nasal vaccine used a live virus. But both vaccines tested less powerful than needed to fight H1N1 infection.

When determining the efficacy of the vaccine, researchers decide how much of the deactivated virus is necessary to ensure that enough antibodies are created. After vaccines are produced, they are regularly tested to ensure that the level of antibody-creating virus remains above the baseline needed to remain effective, says to Lance Rodewald, M.D., director of the Division of Immunization Services in the National Center for Immunization and Respiratory Diseases at the Center for Disease Control and Prevention. He spoke to reporters last week as part of a training session for the Association of Health Care Journalists. Most vaccines lose some potency over time, which is why they come with expiration dates. But potency levels H1N1 vaccines, he said, are degrading much faster than usual. So when these drug companies test for efficacy, the saw that the vaccine was about to become or had just become too weak to be effective. Those who have received the vaccine already don't need to worry─they most likely received the vaccine at a proper potency.

But WHY is the H1N1 vaccine losing power so quickly? Scientists don't know, says Rodewald, but they speculate that the viruses in the serum is especially sticky─clinging to the walls or being absorbed into the syringes in which they're housed. How to make less absorbent syringes, or a less sticky vaccine have yet to be determined.

Currently, the recalled vaccines are not an issue of life and death. But if, as predicted, there's a second wave of influenza outbreak, or if swine flu returns as the dominant flu strain next season, it's a problem that needs to be resolved as quickly as possible.