The highly transmissible omicron variant now accounts for almost all COVID-19 cases around the world, but a subvariant ― omicron BA.2 ― has emerged that appears to be even more contagious. Cases of omicron BA.2 are limited in the U.S., but COVID-19 experts at Mayo Clinic say the number is growing, especially overseas.

"In the U.S., we have identified cases in about half of the states, but it's about 1% or less of all of the COVID cases occurring. Now take another country like Denmark, where they had very high immunization rates. About 40% to 50% of their cases are this new BA.2 sublineage, so it's quite variable at this early juncture," says Dr. Gregory Poland, director of Mayo Clinic's Vaccine Research Group.

Watch: Dr. Gregory Poland discusses the omicron BA.2 subvariant.

Journalists: Broadcast-quality sound bites are in the downloads at the end of this post. Please courtesy: Mayo Clinic News Network. Name super/CG: Gregory Poland, M.D./Vaccinology/Mayo Clinic.

Scientists are tracking the rise in cases of omicron BA.2, which they say is even more contagious than the original omicron variant, which is also known as BA.1.

"The best estimates are that it's about 1½ times more infectious or transmissible than omicron was. And, remember, omicron was quite a bit more transmissible than delta, which was more transmissible than alpha," says Dr. Poland.

He says the good news is that omicron BA.2 does not seem to cause more severe illness than the original omicron variant.

"This is early, (but) there does not seem to be evidence that it may be more virulent. That is, it does not cause any worse disease than the original omicron strain. And that's a good thing," says Dr. Poland.

Experts also say that, at this point, BA.2 does not appear to reduce the effectiveness of being fully vaccinated for COVID-19.

"And, remember, we've watched this movie five times already in the last two years because we are not seeing people wear masks and because they are unvaccinated or incompletely vaccinated. We are seeing a subvariant arise called BA.2 that's even more infectious. This is going to continue to happen and infect every unvaccinated person until people are vaccinated and until they're wearing a mask. You can choose to ignore these facts ― these clear data ― but the virus could care less what we think. The virus is going to find people who do not have protective immunity and infect them," says Dr. Poland.

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Information in this post was accurate at the time of its posting. Due to the fluid nature of the COVID-19 pandemic, scientific understanding, along with guidelines and recommendations, may have changed since the original publication date. 

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