Vaccination halved the risk of influenza-associated hospitalization among adults during the 2015‒2016 US influenza A(H1N1)pdm09-predominant season, a recent study found. Most of the adults in the study were at increased risk of serious influenza complications due to comorbidity or age. Adults aged ≥18 years admitted to 8 US hospitals with acute respiratory illness and testing positive for influenza by PCR were cases; those testing negative were controls. Researchers analyzed data from 236 cases and 1,231 controls (mean age 58 years). They found:
- >90% of patients had ≥1 comorbidity elevating risk of influenza complications.
- 50% of cases and 70% of controls were vaccinated.
- Vaccination was 51% and 53% effective in preventing hospitalization due to influenza A(H1N1)pdm09 and influenza B virus infection, respectively.
- Vaccine was protective for all age groups.
Ferdinands JM, Gaglani M, Martin ET, HAIVEN Study investigators. Prevention of influenza hospitalization among adults in the US, 2015–16: Results from the US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN). [Published online ahead of print December 14, 2018]. J Infect Dis. doi:10.1093/infdis/jiy723.
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Influenza Vaccination Effectiveness in the US, Clin Infect Dis; ePub 2019 Feb 2; Rolfes, et al
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