SAN FRANCISCO (KPIX 5) — A huge public gathering in New England during the Fourth of July weekend led to a COVID-19 outbreak among people who were already vaccinated, with lab tests pointing to the delta strain of the virus.

The outbreak in Provincetown, Mass., a tourist spot in a county with the state’s highest vaccination rate, is now approaching 1,000 cases, according to new research from the U.S. Centers for Disease Control and Prevention. About three-quarters of those infected were people who were fully vaccinated.

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The CDC says the research along with other data show the COVID delta variant is as infectious as chickenpox, with an infected person  on average infecting eight to nine other people, versus two to three people with the original strain. Vaccinated persons appear to be able to transmit the virus as much as unvaccinated people, the CDC said.

“It falls into the scale of being a much more infectious virus than its predecessors that we dealt with a year ago, six months ago and even four months ago,” said UC Berkeley infectious disease expert Dr. John Swartzberg.

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Swartzberg said the surging delta variant will mean more people will have to wear masks indoors and change other behaviors, and noted COVID-19 vaccines are still highly effective against it and at preventing serious illness and death.

“The good news is that all of the data we have suggests – not only suggests but shows us – that if you’re fully vaccinated, it’s very unlikely you’re going to get sick enough to wind them up in the hospital. Very unlikely,” said Swartzberg. “And even if you wind up in the hospital, it’s extremely unlikely you’re going to die.”

Watch the full interview above.

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