A new version of the omicron variant has been detected in Massachusetts, according to the state Department of Public Health.
The BA.2 subvariant appears to be more transmissible than the original version of omicron, but local and national public health experts emphasize that its presence isn’t a reason for extra concern right now. The virus naturally evolves, and few new versions rise to levels of concern. Initial research on BA.2 indicates that it neither causes more severe disease in patients nor is more able to evade the protection offered by current vaccines.
Dr. Sabrina Assoumou, an infectious disease physician at Boston Medical Center and a member of Boston Mayor Michelle Wu’s COVID-19 Advisory Committee, said vaccines appear to offer the same protection against this new subvariant as the original omicron when it comes to severe disease and death.
“That means that it's going to be even more critical and important to get vaccinated,” Assoumou said. “And especially get boosted, because we know that by getting boosted is how we increase our protection from the omicron variant.”
Bill Hanage, an associate professor of epidemiology at Harvard’s T.H. Chan School of Public Health and co-director of the school's Center for Communicable Disease Dynamics, said the fact that current vaccines are still effective against the BA.2 version of omicron is “extraordinarily important.”
“We do need to remember that we are still seeing, on average, more than 2,000 deaths a day in the United States,” Hanage said. “It could easily be so much worse if the vaccines were not holding up so well against severe disease and death. The great majority of the risk for people right now facing omicron is among the unvaccinated.”
Recent studies have found the newer BA.2 subvariant of omicron could be anywhere from 30% to 50% more transmissible than the older BA.1 version of omicron. But that original version still accounts for the vast majority of cases in the United States; the BA.2 subvariant only makes up 1.5% of total cases in the country right now, according to the CDC.
The BA.2 version of omicron has been dubbed a "stealth" variant at times. Assoumou explained that label has nothing to do with its infectiousness. Rather, she said the earlier omicron version was exceptional in that it left a "signature" in PCR tests. Patients infected with other variants and this new BA.2 subvariant will still get positive results through a PCR, but their samples would also have to undergo genomic sequencing if they wanted to determine which specific coronavirus variant was causing their illness.
Andrew Lover, an assistant professor of epidemiology at UMass Amherst, said experts are carefully watching Denmark, because it has many BA.2 cases. According to the World Health Organization, Denmark is in a surge that’s lasted about three months so far, and has recently recorded more than 50,000 new daily COVID-19 cases on average.
Denmark’s population is a million less than Massachusetts' population. Currently, the state Department of Public Health is reporting new daily cases just over 3,000 on average.
But Denmark's number of deaths and patients being treated in intensive care units are relatively low and are declining from earlier in the surge, according to the Danish Health Authority. About 60% of Danes over 12 having been boosted, and the country recently started scrapping pandemic restrictions.
“We don’t know enough yet to say if or when BA.2 will become a problem,” Lover said in an email. “Denmark is seeing a very protracted wave, which appears to be a mixture of BA.1 and BA.2. Watching this over the next one to two weeks will be very informative for Massachusetts and the rest of the Northeast.”
Assoumou said important indicators in the state are heading downward, including case numbers and hospitalizations. But she added that BA.2 could affect that trajectory and lead to a slow decrease in cases.
"I think overall, I'm cautiously optimistic. … We just need to continue to vaccinate as many people as possible, and also continue to use public health measures," she said. "You know, there's still a lot of COVID out there.”