Influenza vaccine effectiveness against hospitalization during the 2018/2019 season among older persons aged ≥ 75 years in Japan: The LIFE-VENUS Study. Issue 34 (12th August 2022)

• Record Type: Journal Article
• Authors: Mimura, Wataru; Ishiguro, Chieko; Fukuda, Haruhisa
• Is Part Of: Vaccine. Volume 40:Issue 34(2022)
• Page Start: 5023
• Page End: 5029
• Publication Date: 2022-08-12
• Subjects: Influenza -- Vaccine effectiveness -- Older persons -- Pneumonia; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2022.07.002
• Languages: English
• ISSNs: 0264-410X

Abstract

Highlights: We analyzed influenza vaccine effectiveness during the 2018/2019 season in Japan. The population-based study cohort comprised older persons aged ≥ 75 years. Vaccine effectiveness against hospitalization was 28.9%. This is Japan's largest cohort study on influenza vaccine effectiveness to date. Abstract: Background: Older persons are recommended to receive annual influenza vaccinations due to their increased susceptibility to influenza infections and related complications. Routine assessments of influenza vaccine effectiveness (IVE) in older persons may help to improve vaccine development and vaccination strategies, but there is a lack of consistent epidemiological data from Japan. This study aimed to evaluate IVE against hospitalization during the 2018/2019 season among older persons aged ≥ 75 years in Japan. Methods: This cohort study was conducted using insurance claims data and vaccination records provided by the Longevity Improvement & Fair Evidence - Vaccine Effectiveness, Networking, and Universal Safety (LIFE-VENUS) Study. The study cohort comprised older persons aged ≥ 75 years residing in an urban municipality in Japan. Vaccinated participants were identified through vaccination records from October 2018 to January 2019, and were matched with unvaccinated participants using a 1:1 ratio. The IVE against hospitalization was calculated as (1−hazard ratio) × 100% while adjusting for covariates such as age, sex, comorbidities, previous vaccinations, and care needs levels. Results: We analyzed 30, 881 vaccinated participants matched with 30, 881 unvaccinated participants. Among these, 587 (1.9%) vaccinated participants and 644 (2.1%) unvaccinated participants were hospitalized during the 2018/2019 season. The adjusted IVE against hospitalization was estimated to be 28.9% (16.6–39.4%). Conclusions: The influenza vaccine for the 2018/2019 season showed moderate effectiveness among older persons in Japan. The LIFE-VENUS Study represents a potential platform for the continued monitoring of IVE among the older Japanese population.