On March 22 the World Health Organization announced that the Omicron subvariant BA.2 had become the dominant form of SARS-CoV-2. BA.2 shares many genetic similarities with its close relative BA.1, which fueled a global resurgence in COVID infections in recent months. However, BA.2 is between 30 percent and 50 percent more contagious than BA.1.
Fortunately, evidence so far indicates that disease symptoms caused by BA.2 are not more severe than those caused by BA.1 in vaccinated people or people who were previously infected with SARS-CoV-2. Moreover, early evidence suggests that reinfections with BA.2 after BA.1 do occur but are rare.
Other factors also govern BA.2’s transmission: vaccine and booster coverage, public health countermeasures and the average age of the population all play a role.