BA.4, BA.5 variants could spark ‘new wave’ of COVID this summer, Massachusetts reports 1,529 new cases

Two omicron subvariants are on the rise across the region, and new evidence about the highly contagious COVID strains means they could spark “a new wave this summer,” according to a local infectious disease expert.

It appears that the variants, known as BA.4 and BA.5, are more transmissible and evade the immune response from prior omicron strains — making natural immunity from past infection or vaccine-induced immunity less effective.

“This could mean a risk for a new wave this summer,” said Davidson Hamer, a Boston University School of Public Health infectious disease specialist.

The recent evidence about the variants “suggests a potential risk for a substantial rise in infections this summer or early fall,” he added. “This is already happening in Europe.”

Both the BA.5 and BA.4 subvariants are now gaining steam locally, with BA.5 representing 28.7% and BA.4 representing 15.3% of new cases in New England, according to the updated CDC variant tracker. Those respective proportions are up from 18.9% and 11.5% last week.

The omicron BA.2.12.1 subvariant now accounts for 51.4% of new cases in New England, according to the CDC variant tracker. That’s down from 61.7% last week.

“BA.4 and 5 are concerning as they seem to evade the immune response that is generated for prior omicron strains, making it more infectious,” said Matthew Fox, a Boston University School of Public Health epidemiology professor. “It may also be more severe, though that is not yet clear.”

“This strain is starting to dominate here, and as such, as we’ve been saying all along, people need to be prepared to take action,” he added. “That could be reducing contacts and increasing masking indoors.”