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Department of Defense study: seasonal influenza vaccination moderately effective against influenza A (H1N1)
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A "moderate degree of protection" against influenza A (H1N1) was seen among military personnel who received seasonal influenza vaccination, according to results of a Department of Defense study presented at the American Society of Tropical Medicine and Hygiene’s 58th Annual Meeting in Washington, D.C.
The results showed that the inactivated vaccination and the live attenuated vaccination were associated with similar levels of protection against influenza A (H1N1).
Researchers at the Department of Defense conducted a surveillance study of influenza-related medical issues among military personnel stationed in the United States between April 2009 and October 2009.
During the study period, 1,205 cases of influenza A (H1N1) were reported among military personnel stationed in the United States. According to the researchers, overall vaccine effectiveness of seasonal influenza vaccination against influenza A (H1N1) was 45%.
The results were adjusted for gender, age, number of prior vaccinations and vaccine type. According to the researchers, further analysis indicated that irrespective of prior vaccination status, older age (defined as patients aged older than 39 years) and prior vaccination were significantly associated with increased vaccine effectiveness.
The results also showed that vaccine effectiveness against severe disease outcome (defined as requiring hospitalization) was higher than against milder outcome (defined as requiring outpatient treatment).