BOSTON — Massachusetts may have to readjust its set-point for herd immunity, thanks to the anticipated dominance of the Delta variant of COVID-19.

At least that’s the view of Samuel Scarpino, an assistant professor at Northeastern University and director of the school’s Emergent Epidemics Laboratory.

“The governor has targeted 60 percent of the entire state for vaccination, which was a good goal pre-Delta,” Scarpino said. “But with this new variant, that’s really not going to be enough to protect unvaccinated individuals like school children.”

Scarpino said you only have to look at Israel to know why that’s not enough. That country, much lauded in recent months for its vaccination efforts, is now feeling the effects of the Delta variant.

“They’re at about 60 percent of the population fully vaccinated and we’re hearing reports of outbreaks in schools in unvaccinated children and rising case numbers due to the Delta variant,” Scarpino said.

That raises the discomforting specter of what might happen come September here. At present, the Delta variant is the cause of around 10 percent of infections in the U.S. But its share is rising fast — and with good reason.

“It’s probably 40 to 60 percent more transmissible than the B.1.1.7 variant,” according to preliminary data, Scarpino said. “There’s quite a bit of risk from this variant especially in undervaccinated populations.”

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