Seasonal Flu Vaccine Unlikely To Protect Against New H1N1 Says CDC

According to the US Centers for Disease Control and Prevention (CDC), vaccination with seasonal flu vaccines made for the 2005 to 2009 seasons is unlikely to protect people against infection by the new A (H1N1) swine flu virus. Scientists from the federal agency used banked blood samples taken before and after vaccination every year since 2005 and exposed them to the new swine flu virus. They reported the results of their investigations in the 19 May issue of their Morbidity and Mortality Weekly Report (MMWR).

The results showed that although samples from children had no antibodies, samples from adults vaccinated against seasonal flu showed a slight increase in antibodies against the novel influenza A (H1N1) virus but it was not possible to say whether this would be enough to protect them against infection. Because of this they concluded that a vaccine specific to the new strain was needed.

The result is consistent with the fact that the new A (H1N1) virus is genetically more different to the seasonal flu viruses that have circulated in the last few years than the seasonal flu viruses are from each other. 

The new A (H1N1) virus shares only 72-73 per cent of the significant amino acid identity with the seasonal flu viruses, while the seasonal flu viruses shared 97 to 98 per cant among themselves.

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