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Local researchers are ‘cautiously optimistic’ but keeping an eye on a new COVID sub-variant

The Omicron COVID variant changed significantly in ways that allowed it to evade people’s immunity, both from prior infections and from vaccines. A variant of Omicron, BA.2, has a lot in common with its predecessor.Craig F. Walker/Globe Staff

Researchers in Massachusetts said they are keeping an eye on a new version of the Omicron variant, but emphasized that, while much remains unknown, the virus seems not to diverge too much from the original Omicron.

While it’s too soon to know exactly what that means for people who have already been infected with Omicron, experts said it’s possible they may have some degree of protection.

Sub-variant BA.2 — which has not been assigned a Greek letter — shares many characteristics with the COVID variant commonly known as Omicron, also called BA.1. So far, it has been found in several states, including Idaho, Texas, Washington State, California, and New Mexico. It also has been spreading rapidly in Denmark, South Africa, India, and the Philippines.

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“We’ll have to see from people who have recovered from BA.1, how their antibodies in their blood are able to neutralize BA.2 in the laboratory, and extrapolate from there,” said Dr. Daniel Kuritzkes, a professor of medicine at Harvard Medical School and chief of the division of infectious diseases at Brigham and Women’s Hospital.

As with other variants when they first emerge, many questions about BA.2 remain unanswered: Will the sub-variant be more infectious, or cause more severe illness or a higher percentage of deaths? Will vaccines be effective in preventing illness and transmission? Are there implications for long COVID?

“There is very little known about the transmissibility of BA.2 with respect to BA.1,” said Dr. Jeremy Luban, a professor of molecular medicine, biochemistry, and molecular pharmacology at UMass Medical School.

Nor do we know much about its ability to cause severe illness, or its ability to dodge immunity from vaccines or treatment from monoclonal antibodies, he said.

The World Health Organization noted this week that the BA.2 lineage is becoming more common in some countries, though it has not been specifically designated a variant of concern.

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The UK Health Security Agency designated BA.2 a variant under investigation last week, and said it had confirmed 426 cases of the sub-variant dating back to early December. In Denmark, the proportion of BA.2 cases rose from 20 percent of all COVID cases during the last week of 2021 to 45 percent during the second week of 2022, according to the Statens Serum Institut. Researchers in Denmark noted they had not detected a significant change in hospitalizations between BA.1 and BA.2.

While the Delta variant had a relatively small amount of amino acid changes in its spike proteins, Omicron had changed much more significantly in ways that allowed it to evade people’s immunity, both from prior infections and from vaccines. BA.2 has much more in common with its predecessor, the original Omicron variant.

A list of amino acid changes in the SARS-CoV-2 virus between the Delta, Omicron, and BA.2 variants, provided by Dr. Jeremy Luban of the University of Massachusetts Medical School.Dr. Jeremy Luban

“We don’t really know what the significance of BA.2 mutations are going to be,” Luban said. “Especially not in a population that’s already encountered BA.1, the main Omicron.”

More answers will likely come in the next few weeks, but researchers did express a bit of cautious optimism.

One encouraging possibility is that T cells, a type of white blood cell, may be able to confer some degree of help against severe illness, said Dr. Bruce Walker, the founding director of the Ragon Institute of Massachusetts General Hospital, MIT and Harvard.

“It’s T cells that probably have a major effect on disease course, once somebody does become infected,” Walker said.

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He said the BA.2 sequence suggests that T cells, a type of white blood cell central to fighting off pathogens the body has encountered before, may be effective in helping people who have been previously exposed to Omicron avoid severe illness.

“So it’s encouraging that, at least from the T cell side, we may not be protected from getting infected but they should help to mitigate disease,” he said.

Dr. Jacob Lemieux, an infectious disease specialist at Massachusetts General Hospital, said there is reason to monitor emerging variants. But an outbreak as severe as the one caused by the original Omicron variant, which he referred to as BA.1, is not a foregone conclusion.

“I don’t think that it is going to cause the degree of chaos and disruption, morbidity, and mortality that BA.1 did,” Lemieux said. “I definitely don’t want to be seen as spreading the alarm that there’s another variant on the horizon that is going to do what the last one did. I am cautiously optimistic that we are going to continue to move to a better place and frankly — hopefully — one where each new variant on the horizon isn’t news.”


Gal Tziperman Lotan can be reached at gal.lotan@globe.com or at 617-929-2043.