Effectiveness of messenger RNA vaccines against infection with SARS-CoV-2 during the periods of Delta and Omicron variant predominance in Japan: the Vaccine Effectiveness, Networking, and Universal Safety (VENUS) study. (December 2022)

• Record Type: Journal Article
• Authors: Mimura, Wataru; Ishiguro, Chieko; Maeda, Megumi; Murata, Fumiko; Fukuda, Haruhisa
• Is Part Of: International journal of infectious diseases. Volume 125(2022)
• Page Start: 58
• Page End: 60
• Publication Date: 2022-12
• Subjects: COVID-19 -- Messenger RNA vaccine -- Vaccine effectiveness -- Population-based cohort study -- Japan; Communicable diseases -- Periodicals; Communicable Diseases -- Periodicals; Communicable diseases; Periodicals; Electronic journals; 616.9
• DOI: 10.1016/j.ijid.2022.10.001
• Languages: English
• ISSNs: 1201-9712

Abstract

Highlights: This report contains the first results of the Vaccine Effectiveness, Networking, and Universal Safety (VENUS) study conducted in Japan. This cohort study assessed COVID-19 messenger RNA vaccine effectiveness (VE). VE of two doses against symptomatic infection was 89.8% during the Delta wave. VE of two doses against symptomatic infection was 21.2% during the Omicron wave. VE of three doses against symptomatic infection was 71.8% during the Omicron wave. Abstract: Objectives: We aimed to evaluate COVID-19 messenger RNA vaccine effectiveness during the Delta- and Omicron-predominant periods in Japan. Methods: We conducted a population-based cohort study among individuals aged 16–64 years during two periods: the Delta-predominant period (July 1–December 31, 2021) and the Omicron-predominant period (January 1–March 29, 2022). Results: When comparing individuals who were vaccinated with those who were unvaccinated, the effectiveness of a second dose against symptomatic infection was 89.8% (95% confidence interval [CI]: 80.5–94.7%) during the Delta-predominant period and 21.2% (95% CI: 11.0–30.3%) during the Omicron-predominant period. The effectiveness of a third dose against symptomatic infection was 71.8% (95% CI: 60.1–80.1%) during the Omicron-predominant period. Conclusion: Vaccine effectiveness against symptomatic infection decreased during the Omicron-predominant period but was maintained by a third dose.