Omicron is constantly evolving to give rise to novel sub-VOCs with greater transmissibility and immune evasiveness, making COVID-19 mitigation a challenging task. Varying immune-evasiveness of Omicron sub-VOCs allows the occurrence of novel SARS-CoV-2 infections. Analysis of immune escape of vaccination or infection-induced immune protection by novel VOCs and sub-VOCs could inform policy-making and guide the development of updated vaccines.
A SARS-CoV-2 infection-only method was used to evaluate the impact of prior anti-SARS-CoV-2 immunity levels against novel BA.4/5 and BA.2 infections between May 2 and July 24, 2022. Additionally, the team evaluated the effects of the VOC-wise duration between the prior and current case of COVID-19 and that of different VOC infections on the development of Omicron BA.4/5 and Omicron BA.2 infections.
Results During the study period, 26 % of BA.2 infections and 74% of BA.4/5 infections were identified. During the initial and last weeks, Omicron BA.4/5 caused 3.30% infections and 99% infections. BA.4/5-infected individuals were usually younger compared to BA.2-infected individuals. The fraction of individuals with current SARS-CoV-2 infections was more significant for Omicron BA.4/5 infections, weekly and during the entire study period.
Prior COVID-19 history enhanced the risk of BA.4/5 infections, compared with Omicron BA.2 infections . Among previously infected individuals, the duration between SARS-CoV-2 infections was shorted among BA.4/5-infected individuals than BA.2-infected individuals, with median intervals of 182 days versus 206 days, respectively).