The newer and most contagious omicron subvariants of the SARS-COV-2 virus, known as BA.4 and BA.5, now make up the majority of infections in New England, according to data released by the CDC this week.
Public health experts in Massachusetts say the subvariants are more contagious but their severity is still unclear. They stressed it bears watching in the summer months and that current public health tools are still very effective against BA.4 and BA.5, including masking indoors, avoiding crowds and close contact with strangers and getting a first or second booster shot.
Andrew Lover, an assistant professor of epidemiology at the School of Public Health and Health Sciences at UMass Amherst, pointed to the constant churn of new SARS-COV-2 variants, driven in part by low vaccination rates in some less-developed parts of the world. Lover said it creates a level of unpredictability that doesn’t bode well for a lasting lull in COVID-19 cases.
“Certainly in the last two summers, we’ve seen fairly low case counts,” Lover said. “And I think everyone had been kind of hoping or assuming that this summer would look pretty similar, all in all. And we may not be quite so lucky.
“It certainly is a bit concerning,” he added. “More than a few countries in Europe right now, as well as Israel, are seeing some pretty significant increases in cases and hospitalizations with increased BA.5. And there’s at least some evidence that suggests the symptoms can be pretty severe with BA.5 — but we don’t have great data on that yet.”
Lover said BA.5 is “quite capable of outcompeting most of the other variants in circulation right now — so that alone says that it’s a really, really very fit virus. And so that is definitely worrisome.”
But Bill Hanage, an associate professor of epidemiology in the Center for Communicable Disease Dynamics at Harvard's T.H. Chan School of Public Health, emphasized that it’s still too early to tell if the subvariant is more severe, or just more contagious.
Hanage said the increased transmissibility of BA.5 alone would be expected to drive up the number of severe infections. But he adds that BA.5 has already caused some sizable surges in cases in South Africa and Portugal, and that in both places data on hospitalizations and deaths is not particularly worse than with earlier omicron variants.
“So BA.5 is just the next chapter in the story,” Hanage said. “And it’s not as good as it would be if BA.5 did not exist, but there isn’t reason, at the moment, to think that it’s really turning the page in a serious way when it comes to hospitalizations and deaths.”
Still, the subvariants’ increased contagiousness prompted the FDA to tell vaccine makers last week that booster shots for fall should be updated to target BA.4 and BA.5. Hanage said he has his doubts about the wisdom of that given how quickly the variants’ prevalence can change.
“Let’s get real, playing whack-a-mole with variants is kind of a mug’s game,” Hanage said. “Six months ago, BA.4 and BA.5 were scarcely ‘a glint in omicron’s eye,’ and now they are going global — BA.5, in particular.”
There are already different and possibly concerning variants on the horizon, he said, like one detected in India, BA.2.75, that has more genetic changes than other variants, which often can be an indicator of newly evolved danger.
For those who have already been infected and are vaccinated and boosted, Hanage said they are very unlikely to become severely ill from being infected with BA.4 or BA.5. But, if they are reinfected, he said they could still be contagious more than five days after testing positive, so a bigger consideration might become who else they would infect.
The shrinking minority of Massachusetts residents who have not yet contracted COVID-19 tend to be more vulnerable to the virus, he said. It’s an older population that’s been extremely careful to avoid infection so far, so even with a variant whose severity is unclear, those residents are still vulnerable.
“And as we see people who are in more vulnerable categories become infected, we might see more severe infections, more burdens in hospitals,” Hanage said. “And so this is something which we should still be watching pretty closely, even if at the same time, we should be straight with folks and be very clear that we are in no way in a position like we were in 2020 or even 2021.”