Reduced clinical severity during 2022 Shanghai Spring epidemic of SARS-CoV-2 omicron BA.2 variant infection—an integrated account of virus pathogenicity and vaccination effectiveness.

A study conducted during the 2022 Shanghai Spring epidemic of the SARS-CoV-2 omicron BA.2 variant found that the variant had high infection rates but reduced severity of COVID-19. The study analyzed data from 10,258 confirmed COVID-19 cases and found that the omicron BA.2 variant had a low ratio of inpatients suffering from pneumonia. In addition, the study evaluated the effectiveness of inactivated vaccines and found that they reduced the incidence of pneumonia, severe outcomes, and disease progression. The study also found that T cell responses played an important role in reducing the risk of pneumonia and disease progression. Overall, the study suggests that the reduced severity of the epidemic was likely due to the low pathogenicity of the omicron BA.2 variant and the effectiveness of inactivated vaccines. [Extracted from the article]