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Studies: Flu vaccine effectiveness waned over 2011-12 season
http://www.cidrap.umn.edu/cidrap/content/influenza/general/news/jan3113waning.htmlIt's been more or less an article of faith that influenza vaccination in the fall will protect a person through the winter flu season, but three studies published today in Eurosurveillance are challenging that view.
All three studies suggest that during the 2011-12 flu season, the vaccine provided modest protection at first, but its effectiveness dropped sharply after 3 or 4 months.
A multicenter study by researchers in eight European countries indicated that overall vaccine effectiveness (VE) against influenza A/H3N2 in the first months of the season was 38%, but after mid-February it dropped to -1%.
Similarly, British researchers report that the vaccine had an overall effectiveness of 43% against H3N2 viruses from October 2011 to January 2012, but it dropped to 17% for February through April. And a study from Navarre, Spain, yielded similar findings, with overall VE of 61% against all flu types for the first 100 days after vaccination but zero effectiveness seen after 119 days.
"The concept that vaccine protection can be so short-lived provides a challenge for public health policy," says the British report. The authors say the findings raise the question of whether a second dose of seasonal vaccine might be needed for late-season outbreaks, and also point up "the pressing need for the development of influenza vaccines which provide better and longer-lasting protection."
All three studies suggest that during the 2011-12 flu season, the vaccine provided modest protection at first, but its effectiveness dropped sharply after 3 or 4 months.
A multicenter study by researchers in eight European countries indicated that overall vaccine effectiveness (VE) against influenza A/H3N2 in the first months of the season was 38%, but after mid-February it dropped to -1%.
Similarly, British researchers report that the vaccine had an overall effectiveness of 43% against H3N2 viruses from October 2011 to January 2012, but it dropped to 17% for February through April. And a study from Navarre, Spain, yielded similar findings, with overall VE of 61% against all flu types for the first 100 days after vaccination but zero effectiveness seen after 119 days.
"The concept that vaccine protection can be so short-lived provides a challenge for public health policy," says the British report. The authors say the findings raise the question of whether a second dose of seasonal vaccine might be needed for late-season outbreaks, and also point up "the pressing need for the development of influenza vaccines which provide better and longer-lasting protection."