BA.2 Variant 1.5x More Infectious Than Original Omicron Strain: Expert

The new COVID-19 Omicron subvariant BA.2 may be more contagious than the original Omicron variant, a top expert from Denmark's top infectious disease authority has said.

The Omicron subvariant, dubbed “stealth Omicron,” could be 1.5 times more transmissible than the BA.1 sub-lineage, preliminary calculations show. However, an analysis by the Statens Serum Institut (SSI), Denmark’s top infectious disease authority, found no indication of an increase in the risk of hospitalization for the BA.2 subvariant.

"There is some indication that it is more contagious, especially for the unvaccinated, but that it can also infect people who have been vaccinated to a greater extent," SSI's technical director and chief epidemiologist Tyra Grove Krause said in a Wednesday media briefing.

"There is no evidence that the BA.2 variant causes more disease, but it must be more contagious," Danish Health Minister Magnus Heunicke said at the news conference.

The “stealth Omicron” subvariant was first discovered among virus genome data submitted by South Africa, Australia and Canada. Since then, the offshoot variant has been detected in nearly 50 countries across the globe.

At least 92 cases of the BA.2 subvariant have been detected in South Africa, 607 in the United Kingdom and 54 in the United States, according to Outbreak.info, a global COVID-19 dashboard supported by the Centers for Disease Control and Prevention (CDC) and the National Institute for Allergy and Infectious Diseases (NIAID).

The dashboard also indicated that there have been 10,811 cases of the “stealth Omicron” reported worldwide, including Denmark where the subvariant has become the dominant strain in the second week of January, accounting for 60% of all COVID-19 cases in the country.

In comparison, the subvariant only accounted for 20% of all coronavirus infections in the country in the final week of December, data from GISAID showed.

Not much is known about the subvariant. However, some scientists and health experts have warned about the offshoot variant that is harder for lab-based PCR tests to detect. While a person showing symptoms attributed to “stealth Omicron” may test positive for COVID-19 in all usual tests, they may not necessarily test positive for BA.2.

The World Health Organization (WHO) noted that the new subvariant has some mutations not found in the original Omicron strain. However, they have yet to classify “stealth Omicron” as a variant of concern.