Close

Vaccine effectiveness against acute respiratory illness hospitalizations for influenza-associated pneumonia during the 2015-2016 to 2017-2018 seasons, US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN).

Abstract

Influenza vaccination was modestly effective among adults in preventing hospitalizations and the need for intensive care associated with influenza pneumonia. VE was significantly higher against A (H1N1)pdm09 and was low against A (H3N2) and B.

Of 4,843 adults hospitalized with ARI included in the primary analysis, 266 (5.5%) had 'definite/probable pneumonia' and confirmed influenza. Adjusted VE against hospitalization for any radiographically confirmed influenza-associated pneumonia was 38% (95% confidence interval [CI]): 17%-53%); by type/subtype, it was 74% (95% CI: 52%-87%), influenza A (H1N1)pdm09; 25% (-15% to 50%), A (H3N2); and 23% (95% CI: -32% to 54%), influenza B. Adjusted VE against intensive care for any influenza was 57% (95% CI, 19%-77%).

Among adults aged ≥18 years admitted to 10 US hospitals for acute respiratory illness (ARI), clinician-investigators used keywords from reports of chest imaging performed during 3 days around hospital admission to assign a diagnosis of 'definite/probable pneumonia'. We used a test-negative design to estimate VE against hospitalization for radiographically identified laboratory-confirmed influenza-associated pneumonia, comparing RT-PCR confirmed influenza cases with test-negative subjects. Influenza vaccination status was documented in immunization records or self-reported, including date and location. Multivariable logistic regression models were used to adjust for age, site, season, calendar-time, and other factors.

Evidence for vaccine effectiveness (VE) against influenza-associated pneumonia has varied by season, location, and strain. We estimate VE against hospitalization for radiographically identified influenza-associated pneumonia during 2015-2016 to 2017-2018 seasons in the US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN).

MIDAS Network Members

Citation: