Omicron BA.2 sub-variant now nearly a quarter of new COVID cases in U.S., CDC estimates


The BA.2 sub-lineage of the Omicron variant now makes up nearly a quarter of new COVID-19 infections nationwide, the Centers for Disease Control and Prevention estimated Tuesday, up from round 1 in 10 new cases simply a week prior. 

Since January, Omicron has made up just about all new infections in the U.S. Like in many nations overseas, most cases in the U.S. had been attributable to a sub-lineage of Omicron generally known as BA.1. But whereas each BA.1 and BA.2 may be traced again to some of the earliest samples gathered of Omicron, BA.2 has solely just lately begun to climb in prevalence. 

BA.2’s prevalence is the best in the Northeast, in response to the CDC’s “Nowcast” estimates published Tuesday. In the area spanning New York and New Jersey, the company estimates 39.0% of circulating viruses are BA.2. In New England, prevalence of BA.2 is at 38.6%.

The new estimates come because the sub-lineage has raised issues overseas, the place it has grown to dominate cases reported worldwide — together with in nations which can be now going through a renewed surge of infections simply as that they had moved to raise many of their pandemic restrictions.

In China, authorities have moved to reimpose strict lockdowns to curb BA.2 outbreaks in a number of cities.

However, the rise in BA.2’s proportion in the U.S. comes because the CDC has continued to trace a nationwide slowdown in the tempo of new COVID-19 hospitalizations and cases.

Those developments seem to carry true even in the areas with the best share of BA.2 cases, although early-warning information gathered by the agency from wastewater samples does counsel some communities would possibly quickly see an uptick.

“Although the proportion of infections with BA.2 is increasing in the U.S., COVID-19 cases are now declining, so it is likely that absolute numbers of BA.2 infections are not increasing as quickly as they might seem from just looking at the proportion that are BA.2,” Dr. Deborah Dowell, the CDC’s chief medical officer for the company’s COVID-19 response, mentioned over the weekend. 

Dowell, talking at a webinar hosted by the Infectious Diseases Society of America, mentioned a key distinction between BA.1 and BA.2 had enabled some researchers to “quickly differentiate these sub-lineages.”

Like the Alpha variant, which emerged in 2020, BA.1’s mutations had led to an error in some COVID-19 exams. This “S-gene target failure,” which most Delta variant cases had not brought on, helped authorities rapidly distinguish Omicron cases and estimate the pace of Omicron’s preliminary rise on the time.

BA.2 doesn’t trigger the identical failure, ensuing in some misleadingly nicknaming it a “stealth variant.” However, after BA.1 had reached just about 100% of new infections earlier this year, the identical distinction is definitely serving to researchers quickly analyze BA.2’s rise.

“Although BA.2 does seem to be growing as a proportion of sub-lineages in the United States, it’s not nearly as quickly as we’ve seen in some other countries. The doubling time in the United States actually seems to be slowing down,” mentioned Dowell. 

Using S-gene goal failure in the United Kingdom, well being authorities recently estimated that BA.2 was now the bulk of new infections in most elements of the nation. 

“The speculation I’ve seen is that it may extend the curve going down of case rates of Omicron, but is unlikely to cause another surge the way we’ve seen, that we saw initially with Omicron,” Dowell added later. 

Why federal well being officers say BA.2 is “high on our radar”

Preliminary analysis abroad, together with from Qatar and Denmark, counsel that BA.2 is unlikely to trigger many reinfections of individuals who survived a case of BA.1 earlier in the Omicron wave. Early findings out of South Africa and the United Kingdom additionally counsel the BA.2 variant seems to pose about the identical threat of extreme illness or evading the safety of vaccines, in comparison with BA.1.

Citing these similarities, the World Health Organization mentioned late last month that it will proceed to group each BA.1 and BA.2 collectively as a single variant of concern. 

However, monitoring the unfold of BA.2 is vital in half as a result of it might considerably change some of the choices medical doctors need to deal with probably the most susceptible COVID-19 sufferers. 

An increase in BA.2’s prevalence could possibly be a boon for these scrambling for programs of Evusheld, an antibody drug manufactured by AstraZeneca to guard immunocompromised Americans. While BA.2 seems to retain “near-full susceptibility” to Evusheld, the Food and Drug Administration just lately warned that doses would need to be doubled to guard towards BA.1.

However, a surge in BA.2 cases might sideline sotrovimab, a monoclonal antibody drug produced by GlaxoSmithKline and Vir Biotechnology. Early laboratory research counsel BA.2 might considerably scale back the effectiveness of the remedy. 

“BA.2 is high on our radar,” Dr. Derek Eisnor, the federal official charged with main the distribution of COVID-19 medication on the Department of Health and Human Services, informed a webinar last month.

Eisnor acknowledged the “Achilles heel” new variants pose to monoclonal antibody therapies, however pointed to different choices — just like the COVID-19 antivirals drugs from Pfizer and Merck — which thus far appear to remain efficient at treating BA.2 infections.

“I think in the future, where we may be handicapped with some of our [monoclonal antibodies] becoming inefficacious and again being on pause, or having to be limited in their use, this is where our oral antivirals can really shine and hopefully that helps a little bit,” mentioned Eisnor. 

Alexander Tin

CBS News reporter protecting public well being and the pandemic.