Effectiveness of influenza vaccination in infants and toddlers with and without prior infection history: The Japan Environment and Children's Study

Hiroshi Yokomichi; Reiji Kojima; Sayaka Horiuchi; Tadao Ooka; Yuka Akiyama; Kunio Miyake; Mie Mochizuki; Sanae Otawa; Ryoji Shinohara; Zentaro Yamagata; Japan Environment and Children's Study Group

doi:10.1016/j.vaccine.2021.02.044

Effectiveness of influenza vaccination in infants and toddlers with and without prior infection history: The Japan Environment and Children's Study

Vaccine. 2021 Mar 26;39(13):1800-1804. doi: 10.1016/j.vaccine.2021.02.044. Epub 2021 Mar 5.

Authors

Affiliations

¹ Department of Health Sciences, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
² Department of Health Sciences, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
³ Birth Cohort Centre, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
⁴ Department of Health Sciences, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
⁵ Department of Health Sciences, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
⁶ Department of Health Sciences, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
⁷ Department of Paediatrics, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
⁸ Birth Cohort Centre, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
⁹ Birth Cohort Centre, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].
¹⁰ Department of Health Sciences, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan; Birth Cohort Centre, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan. Electronic address: [email protected].

PMID: 33685777
DOI: 10.1016/j.vaccine.2021.02.044

Abstract

We calculated the Poisson-regression-adjusted relative risk (RR) of new influenza infection by vaccination, prior infection, and vaccination after prior infection in a large Japanese birth cohort, using data from ≤89,253 children aged 6 months to 3 years. The effectiveness of risk reduction (1 - RR) by vaccination at ages 1.5-3 years was 21%-31%. The RR of new infection after prior infection vs. no prior infection was 2.58-19.3 at age 1-3 years. An analysis of the 1 - RR data stratified by having at least one senior sibling and/or attending nursery school revealed that vaccination reduced the RR by 22%-40%. The 1 - RR of new infection was 21% in 3-year-old children who were vaccinated after prior infection. All these findings are statistically significant. The results consistently indicate that, regardless of having at least one senior sibling, attending nursery school, and/or being previously infected with influenza, infants and toddlers will benefit from influenza vaccination.

Keywords: Children; Influenza infection; Influenza vaccine; Japanese; Relative risk; Vaccine effectiveness.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Child, Preschool
Humans
Infant
Influenza Vaccines*
Influenza, Human* / prevention & control
Japan / epidemiology
Schools
Schools, Nursery
Vaccination

Substances

Influenza Vaccines