Disease profile and plasma neutralizing activity of post-vaccination Omicron BA.1 infection in Tianjin, China: a retrospective study

2022-01-08

SARS-CoV-2 Omicron variant BA.1 first emerged on the Chinese mainland on January 8, 2022, in Tianjin and caused a large wave of infections.1 Four rounds of mass testing of its ~14 million residents were launched on January 9, 12, 15, and 20, respectively. As of February 7, 2022, a total of 430 individuals were tested positive for Omicron BA.1, with no new infections detected for the following 16 days.In the Chinese mainland, the most delivered vaccines are inactivated vaccines. As of January 8, 2022, up to 93.2% of Tianjin’s residents had been vaccinated with at least one dose.2 We investigated the protection conferred by vaccination against Omicron BA.1 by examining the breakthrough infections among vaccinees as compared with unvaccinated cases. Our study population comprised all 430 cases during the outbreak ofOmicron BA.1 in Tianjin.