Immunogenicity of influenza vaccine in elderly people: a systematic review and meta-analysis of randomized controlled trials, and its association with real-world effectiveness

Abstract

Background: Older people (≥60 years old) are particularly vulnerable to influenza virus infection, and vaccine is effective in reducing the disease burden in this population. However, it remains obscure whether their antibody response is lower than those of younger adults (18–60 years old). Thus, this meta-analysis was performed to compare the immunogenicity of influenza vaccines and understand their association with real-world vaccine effectiveness (VE) between these two age groups. Methods: A systematic literature search was conducted to identify relevant studies from Jan 01, 2008 to Nov 10, 2018. These are randomized controlled trials that included older adult samples, which assessed the immunogenicity of inactivated quadrivalent influenza vaccines produced in embryonated eggs. We excluded the studies focused only in children or adults. The outcomes were seroprotecton rate (SPR) and seroconversion rate (SCR). Results: Six studies were eventually included in the present meta-analysis (7,976 participants). For the SPR, the pooled risk ratio (RR) was 0.92 (95% CI: 0.90–0.94, I2 = 66%, P