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Influenza vaccine effectiveness low among US military personnel
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There was a low level of protection against influenza among US military personnel during the 2010-2011 season. However, compared with live attenuated vaccine, higher protection was observed with the trivalent inactivated vaccine, researchers from the Armed Forces Health Surveillance Center suggest.
They also found that although TIVs offered more protection than LAVs, there was no protection for influenza A/H1N1 for either vaccine type.
“Our study is important because we examined influenza case data at the subtype level,” Angie Eick-Cost, PhD, special studies lead at the Armed Forces Health Surveillance Center, told Infectious Disease News. “The finding of varying protection by subtype is important for U.S. vaccine policymakers to know because it can affect their decisions on vaccine formulations and strain selections for next year’s influenza vaccine.”
For the study, data were obtained from the Defense Medical Surveillance System. From Sept. 1, 2010 to April 30, 2011, there were 603 individuals who had laboratory-confirmed, influenza-associated illness. The study also included two comparison groups: one group with test-negative, non-influenza respiratory illnesses and one group of healthy controls. Immunization data were also obtained.
When compared against the test-negative controls, vaccine effectiveness was higher for the TIV: 53% (95% CI, 25 to 71) vs. –13% (95% CI, –77 to 27) for the LAV. When compared against the healthy controls, the TIV also prevailed in vaccine effectiveness: 23% (95% CI, –1 to 42) vs. 11% (95% CI, –15 to 31) for the LAV.
A 58% vaccine effectiveness was observed (95% CI, 21 to 78) against influenza A/H3N2 and a 34% vaccine effectiveness (95% CI, –122 to 80) found for influenza B. The researchers found no protection against influenza A/H1N1 for either of the vaccine types. The overall vaccine effectiveness was 37% (95% CI, –10 to 64).
“This study emphasizes the need to conduct yearly assessments of influenza vaccine effectiveness, especially when the vaccine components change and when novel influenza strains are circulating,” Eick-Cost said. “It would be interesting to further investigate the apparent lack of protection by the vaccine against the A/H1 pandemic influenza strain through immunologic studies.”
References:
Eick-Cost AA. PLoS One. 2012;doi: 10.1371/journal.pone.0041435
Disclosures:
The researchers report no relevant financial disclosures.