Estimation of mRNA COVID-19 Vaccination Effectiveness in Tokyo for Omicron Variants BA.2 and BA.5 -Effect of Social Behavior-

Variability of COVID-19 vaccination effectiveness (VE) should be assessed with a resolution of a few days assuming that VE is influenced by public behavior and social activity. Here the VE for the Omicron variants (BA.2 and BA.5) is numerically derived for Japan’s population for the second and third vaccination doses. We then evaluated the daily VE variation caused by our social behavior from the daily data reports for Tokyo. The vaccination effectiveness for Omicron variants (BA.1, BA.2, and BA.5) are derived from the data of Japan and Tokyo with a computational approach. In addition, the effect of different parameters regarding human behavior on VE is assessed using daily data in Tokyo. The individual VE for the Omicron BA.2 in Japan was 61% (95%CI: 57%–65%) for the vaccination second dose from our computation, whereas that for the third dose was 86% (95% CI: 84%–88%). The individual BA.5 VE for the second and third doses are 37% (95% CI: 33%–40%) and 63% (95% CI: 61%–65%). The reduction of daily VE from estimated value was close correlated to the number of tweets related to social gathering in Twitter. The number of tweets considered here would be one of new candidates for VE evaluation and surveillance affecting the viral transmission.