The BA.2 Omicron subvariant is being pegged as being responsible for causing more than half of the COVID-19 cases in the United States, according to America’s public health agency.
Estimates from the Centers for Disease Control and Prevention (CDC) updated March 29 had BA.2 as being behind 55 percent of the cases recorded in the week ending March 26.
That was up from 39 percent the previous week and 28 percent the week before that.
The estimates may be revised. The CDC revised the figures in late 2021 and did so again Tuesday, moving the estimates up for mid-March.
BA.2 is increasingly displacing other subvariants of Omicron, a strain of the CCP (Chinese Communist Party) virus, also known as SARS-CoV-2, the virus causes COVID-19.
Emerging data indicate that BA.2 is more transmissible than Omicron and other subvariants, but “there’s no evidence that BA.2 variant results in more severe disease, nor does it appear to be more likely to evade our immune protection,” Dr. Rochelle Walensky, the CDC’s director, told reporters during a recent briefing.
Omicron itself is much better than Delta at evading protection bestowed by vaccines or prior infection, especially the former. The vaccines authorized or approved in the United States provide little shielding against infection from Omicron, though they have held up better against severe disease.
Because of the waning effectiveness, U.S. regulators on Tuesday authorized a fourth shot of the Moderna and Pfizer vaccines for tens of millions of Americans, and the CDC quickly recommended those eligible get one.
BA.2 also appears to render some treatments less or ineffective, including a monoclonal antibody made by GlaxoSmithKline and Vir Biotechnology.
Some experts fear BA.2 could cause a fresh wave of COVID-19 infections and hospitalizations in the United States, but that has not turned out to be the case so far.
The 7-day moving average of cases has continued to drop in recent weeks, hitting a new low of 26,190—the lowest since July 13, 2021—according to data reported to the CDC.
Hospital admissions with COVID-19 have also plunged since a new high in January, with the weekly average going below 13,000 this week.
Deaths attributed to COVID-19 have also kept going down, with just 836 reported Monday.
Under a revised measure introduced by the CDC in February, only 53 counties in the entire country are experiencing high levels of COVID-19.
Over 90 percent are pegged as having low community levels.
The World Health Organization said in a recent report that BA.2 caused about 86 percent of the cases reported to it in the four-week period ending on March 17, but that COVID-19 cases and deaths continued to drop during the week ending on March 20.