Analysis: Flu vaccine effective only 59 percent of time for healthy adults
There are critical gaps in our understanding of the effectiveness of licensed influenza vaccines in the United States, according to a comprehensive study led by the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota. The study is published in the November edition of The Lancet Infectious Diseases, (published online Oct. 25, 2011.)
Michael Osterholm and colleagues from CIDRAP, the Marshfield Clinic Research Foundation, and Johns Hopkins University screened 5,707 medical articles published between 1967 and 2011 for studies of randomized controlled trials and observational studies assessing the reduction in influenza risk after vaccination with licensed vaccines.
Including only those studies that used sensitive and highly specific diagnostic tests to confirm influenza, the authors identified 31 eligible studies that yield the most reliable information on the effectiveness of current influenza vaccines. The analysis included studies published from 1967 to February 2011.
Randomized controlled trials of trivalent inactivated vaccines (TIV) were effective in preventing influenza in eight of twelve (67 percent) seasons and had a combined efficacy of 59 percent against influenza in healthy adults.
The live attenuated influenza vaccine (LAIV) was shown to provide significant protection in nine (75 percent) of 12 seasons against infection and had a combined efficacy of 83 percent against influenza in children aged 6 months to 7 years.
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