By Louisa Moller

BOSTON (CBS) — Even in the rain, Andrew Sharpe wears a mask and a warm demeanor, preaching the benefit of COVID vaccines outside a Hyde Parke supermarket.

“It’s about trust and education,” said Sharpe, the Chair of the Authentic Caribbean Foundation. “COVID has really showed the ugly side of not supporting our community at the level that we ought to.”

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It is the kind of grassroots campaign that experts say is crucial right now as the Delta variant of the coronavirus, first identified in India, threatens to be the dominant strain in the U.S. soon.

“This is a variant that is significantly more contagious even than the B 1.1.7 variant we were discussing back in the winter. And there’s some evidence to suggest that perhaps it’s more virulent meaning it could cause a more serious infection when people are infected,” said Dr. Benjamin Linas, Associate Professor of Medicine at Boston Medical School. “If there’s a community that’s not vaccinated, it’s going to look like last winter.”

There have been 175 cases of the variant in Massachusetts, according to GISAID.

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Linas said the variant threatens to create surges through the fall and winter among unvaccinated communities.

“I think we are moving towards a bifurcated epidemic amongst those who are vaccinated where the epidemic is ending — and those who are not, where the Delta variant is just taking off,” Linas said.

There is some good news. Both the Moderna and Pfizer two-dose vaccines appear to maintain their efficacy against Delta.

The state of Massachusetts just reached its goal of vaccinating 4.1 million people, a number that Linas’s research suggests put the Commonwealth very close to herd immunity.

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“We don’t know precisely where that number is. And, effectively, I think we should act as if it’s a hundred percent,” he said.

Louisa Moller