A new study reveals how the SARS-CoV-2 virus evolved from initially prioritizing increased transmissibility to enhanced immune evasion after the Omicron variant emerged according to Weill Cornell Medicine-Qatar (WCM-Q) researchers. Over the course of the pandemic, the virus has rapidly undergone genetic mutations that have led to multiple variants with differing abilities to spread between individuals, cause severe infections and evade the immune system.
The study, published Feb. 5 in Nature, was conducted through a Qatar-based collaboration of six institutions and presents population-level epidemiological analyses on over 1.5 million people, covering the four-year span from when the pandemic began.
The study revealed that before the Omicron variant emerged in late 2021, natural immunity gained from a previous infection provided sustained and robust protection against reinfection, with an estimated effectiveness of around 80%. However, after Omicron became the dominant strain, immune protection was strong only in recently infected individuals and rapidly declined to negligible levels within a year. These trends were consistent whether reinfection was considered as any infection or limited to symptomatic cases.
