The influenza vaccine this season has had little to no efficacy, in particular against the predominant A strains that have been circulating, said researchers from the Centers for Disease Control and Prevention (CDC) today.
They presented new data to the CDC's Advisory Committee on Immunization Practices (ACIP) that suggested the vaccine was only 18% effective for all ages.
It had previously been reported that the influenza vaccine was only 23% effective this year.
There was also a hint that both the inactive and the live-attenuated vaccine offered perhaps no protection against H3N2 A strains this influenza season.
Both vaccines did immensely better in protecting against B strains — at close to 95% effectiveness — but those are more rare.
CDC researchers said that the lower effectiveness against the A strains was likely due to what appears to be a genetic drift since the vaccine was formulated. The CDC reported in January that 70% of the A strains observed in circulation were different from the vaccine strains.
The agency also reported — again — that the live-attenuated vaccine (MedImmune's FluMist) does not appear to be very effective in children.
This countered what the CDC had previously advised, when it told physicians to choose the nasal spray over the vaccination.
The ACIP panel voted to approve language showing no preference for next influenza season that either FluMist or an inactive vaccine would be considered appropriate for healthy children aged 2 to 8 years who have no contraindications.
The panel also voted that it would express no vaccine preference for those aged 2 to 49 years.
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