BA.2 'Stealth' Omicron Variant Now in 74 Countries, Dominant in at Least 2

The Omicron variant sub-type BA.2, informally dubbed "stealth Omicron." has spread to at least 74 countries worldwide, data shows.

BA.2 has accounted for an increasing proportion of COVID cases in many countries compared to the BA.1 Omicron sub-type, which has been largely dominant so far.

Data has suggested for weeks that BA.2 appears to have a significant growth advantage over BA.1. The extent of any other changes, however, remain less clear.

Outbreak.info, which collects variant data from the virus genome database GISAID, shows that as of Wednesday BA.2 had been found in 74 countries and 47 U.S. states.

Despite BA.2's observed growth advantage, the variant appears to have been reported as dominant in only a couple of countries—Denmark and South Africa—though it's possible it may be dominant in others.

On February 3, Denmark's Statens Serum Institut (SSI) reported that BA.2 accounted for 69 percent of new COVID cases and was expected to account for up to 100 percent of new cases by the middle of this month.

More recently, on February 10, John Nkengasong, director of the Africa Centres for Disease Control and Prevention (CDC), said in a press briefing that BA.2 had become "the predominant variant" in South Africa.

Nkengasong added that the variant had been found in other African nations like Mozambique, Senegal, Botswana, Mauritius, Kenya and Malawi, according to Reuters.

In some countries the variant is spreading noticeably but has yet to make up anything like the majority of cases. The U.K. has been reporting BA.2 cases for several weeks, but according to a technical briefing published by the country's Health Security Agency (HSA) on February 11th, BA.2 accounted for 4.1 percent of cases while BA.1 accounted for 95.4 percent of them.

It should be noted that these figures were based on sequencing data up to January 31st, so they may have changed significantly since then.

Meanwhile in the U.S., BA.2 was estimated to account for 3.9 percent of new sequenced COVID cases between the dates of February 6 and February 12, with other Omicron types accounting for essentially all of the remaining 96.1 percent of cases according to Centers for Disease Control and Prevention (CDC) data.

Dr. Scott Gottlieb, a U.S. physician and former commissioner of the Food and Drug Administration (FDA), has expressed optimism that BA.2 will not make a significant difference to the U.S.' recent decrease in COVID cases. He tweeted last week: "While it may become a dominant strain in time, it appears increasingly unlikely that it will cause a significant change in the downward trajectory of the current epidemic wave."

As mentioned, many aspects of BA.2, such as vaccine resistance and reinfection capability, are still unclear. Reports from the U.K.'s HSA have noted that it appears as though people with booster shots are able to fight off symptomatic disease from BA.2 and BA.1 equally well. The health body also noted on February 11th that there have been no confirmed cases of someone in England being infected with BA.2 after already having had BA.1.

However, a pre-print and non-peer-reviewed study released by Japanese researchers on Tuesday this week suggested BA.2 may be more pathogenic, or capable of causing disease, than BA.1 and that "vaccine-induced humoral immunity fails to function against BA.2 like BA.1". The findings were based on animal studies and "neutralization experiments."

COVID test site
A photo shows a health worker handling what appear to be test tubes at a COVID testing site in Nootdorp, Netherlands, on January 25th, 2022. BA.2 has become dominant in a couple of countries. Patrick van Katwijk/Getty