Rendering of a coronavirus molecule suspended with others on a blue and purple background
Credit: Olga Siletskaya, Getty Images

The fast-spreading sub-variant of omicron, BA.2, now accounts for 55% of U.S. COVID-19 infections, according to the Centers for Disease Control and Prevention.

The new data, for the week ending March 26, reveals a steady rise in prevalence. In late February, the sub-variant was responsible for only 7.4% cases, according to the CDC’s COVID-19 Data Tracker. 

BA.2 currently is more prevalent in certain areas of the United States, with the agency estimating that it accounts for more than 70% of cases in the Northeast, for example. 

Although more highly transmissible than the original omicron variant, the omicron sub-variant does not appear to be more deadly. Yet its dominance has created concerns about COVID-19 treatment efficacy and has left health officials on guard for a potential uptick in infections.

The Food and Drug Administration on Friday restricted the use of one key COVID-19 antibody treatment, sotrovimab, in eight Northeastern states and two territories because the drug is not effective against BA.2. The agency also has approved a second booster shot for U.S. adults aged 50 years and older in anticipation of a possible surge following the rapid spread of the sub-variant throughout Asia and Europe.