New Study Analyzes the Effectiveness of the Influenza Vaccine in the Elderly Population

A recent study found that the flu vaccine is moderately effective at preventing influenza in elderly adults during flu seasons.

While previous meta-analyses have examined the effectiveness of the influenza vaccine in community-dwelling elderly individuals, they failed to account for the effects of patient-level confounders, according to the authors of the current study.
_______________________________________________________________________________________________________________________________________________
RELATED CONTENT
How Long Does Maternal Influenza Immunization Protect Infants?
CDC: New Recommendations for Influenza Vaccine With Egg Allergies
_______________________________________________________________________________________________________________________________________________

They performed a meta-analysis using studies previously included in aggregate data meta-analyses with test-negative design case-control studies, and contacted authors for individual participant data. Twenty-three out of 53 datasets were received and included in the meta-analysis, and 6 additional datasets were provided by data collaborators.

Generalized linear mixed model was used to calculate adjusted vaccine effectiveness based on vaccine match to the circulating strains of influenza virus and intensity of virus activity at the time.  In addition, subgroup analyses were performed to estimated vaccine effectiveness based on hemisphere, age, and health status.

The effectiveness of the vaccine was defined as the relative reduction in risk of laboratory-confirmed influenza in vaccinated patients compared to unvaccinated patients.

A total of 4975 participants were included in the meta-analysis, of whom 3146 were controls.

Their findings showed that the influenza vaccine was significantly effective during epidemic seasons, regardless of vaccine match status. Conversely, seasonal influenza vaccination did not show significant effectiveness during non-epidemic seasons.

“We found substantial variation in vaccine effectiveness across virus types and subtypes, with the highest estimate for A H1N1 pdm09 (53·19%, 10·25–75·58) and the lowest estimate for B virus types (−1·52%, −39·58 to 26·16),” the researchers wrote.

No significant differences were observed between subgroups, however the influenza vaccine showed a protective effect in elderly people with cardiovascular disease, lung disease, or were 75 years old and younger.

“More research is needed to investigate factors affecting vaccine protection (eg, brand-specific or type-specific vaccine effectiveness and repeated annual vaccination) in elderly people,” the researchers concluded.

—Melissa Weiss

Reference:

Darvishian M, van den Heuvel ER, Bissielo A, et al. Effectiveness of seasonal vaccination in community-dwelling elderly people: an individual participant data meta-analysis of test-negative design case-control studies [published online February 8, 2017]. LANCET Respiratory Medicine. doiI: dx.doi.org/10.1016/S2213-2600(17)30043-7.