Updated: Apr 26
Although COVID-19 cases have been receding worldwide, a resurgence around Europe and many parts of China suggests the pandemic is not over yet.
This latest resurgence is mainly fueled by the Omicron Subvariant BA.2 - also known as ‘Stealth Omicron’ or ‘Deltacron’ – and scientists are struggling to understand how it spreads so rapidly, leaving them unable to predict what it might do next. BA.2 already accounts for more than one-third of new COVID-19 cases sequenced in the US.
Scientists believe that the main reason Omicron quickly replaced the Delta variant is its ability to infect and spread among people who had been immune to Delta. It seems sub-variant BA.2 is even better than BA.1 at overcoming immunity, potentially including the protection gained from a BA.1 infection. This could be partly explained by dozens of mutations that distinguish BA.1 from BA.2 – particularly at critical portions of the virus’s spike protein.
Everybody – unvaccinated, double-vaccinated, and boosted individuals – is more susceptible to BA.2 than to BA.1. Still, unvaccinated individuals have an increased risk of BA.2 infection, suggesting that properties of the virus other than immune evasion may contribute to its enhanced transmissibility.