AstraZeneca's MedImmune unit is recalling 4.7 million doses of their nasal spray vaccine voluntarily due to potency concerns. While the slightly lower potency levels noticed during follow-up by the company led them to recall the vaccines, there is no reason for patients who have already been vaccinated to be revaccinated, according to the FDA.

MedImmune is the second H1N1 vaccine distributor over the past month to recall some of their vaccines because of problems with the potency. Around 800,000 doses of pediatric H1N1 injectable vaccine doses produced by Sanofi-Aventis were recalled on December 15 when the company discovered the potency was not high enough. In the case of the MedImmune’s recall, the recall was not for safety concerns, but as a precaution in case some of the affected dosages were being stored. MedImmune’s recall recommends all lots expiring between January 19 and January 26, 2010 be discarded and not administered. The affected lots were distributed in October and November of 2009, when the potency was still full force, according to Norman Baylor with the FDA.

During regular follow-ups on the vaccine, the recalled lots had lost their potency by a small margin. Of the 4.7 million recalled vaccines, there are only 3,000 still left in warehouses. According to MedImmune, there were 13 specific lots of H1N1 nasal spray vaccines released in 2009, which are thought to have potentially lost their potency. 

According to Pat El-Hinnawy, an FDA spokesperson, the action was a "voluntary, non-safety related recall. There are no safety concerns about the vaccine. The decrease in potency is not likely to be clinically significant. Individuals who received doses from the recalled lots do not need to be revaccinated." The company is investigating the reason for the loss of potency in their seasonal flu vaccines, and according to Tor Constantino, a spokesperson for the unit of AstraZeneca, they have not experienced problems with loss of potency in the past.

Sanofi Aventis, CSL of Australia, AstraZeneca unit MedImmune and GlaxoSmithKline are five companies under contract with the U.S. Health and Human Services Department to produce 251 million doses of H1N1 vaccines, in addition to seasonal flu vaccines. There have already been 111 million doses of H1N1 vaccines produced, according to Dr. Anne Schuchat, with the Center for Disease Control.

According to U.S Health officials, cases of the H1N1 virus have continued to decrease across the U.S. and there are plenty of vaccines now available. However, there are not enough Americans being vaccinated. The swine flu is different from the seasonal flu because rather than targeting the elderly or those with weak immune systems, it actually seems to attack more children and young adults. If you or your loved ones have not been vaccinated, now is a great time, because there are plenty of vaccines available.