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Number of breakthrough cases in Mass. nears 8,000; that represents 0.18 percent of those vaccinated

An infectious disease expert says the data underscore that vaccines are effective

Dave Ehlers, left, of South Amityville, N.Y., gets a COVID-19 test at a popup clinic in Provincetown last month.Craig F. Walker/Globe Staff

The number of COVID-19 cases in Massachusetts among people who have been fully vaccinated against the virus has risen to nearly 8,000, according to the latest figures from the state’s Department of Public Health.

Though that seems like a frightening figure, the tally of “breakthrough” infections represents just 0.18 percent of the 4.3 million residents who have been immunized against COVID. Most of the breakthrough cases have been mild.

As of July 31, there have been 395 hospitalizations and 100 deaths among the 7,735 vaccinated individuals who contracted COVID-19.

An infectious diseases doctor said the data underscores that vaccines are effective and breakthrough infections are rare.


Rather than focusing on 0.18 percent of vaccinated individuals have who contracted COVID-19, the focus should be on the 99.82 percent who didn’t contract the virus, said Dr. Philip Landrigan, an epidemiologist who directs the Global Public Health Program at Boston College.

“Anything that protects you against death 99.99 percent of the time is a pretty good deal,” he said.

From now on, the Department of Public Health will release a cumulative count of the state’s breakthrough infectious, hospitalizations, and deaths on a weekly basis. The count will be included in the DPH’s Daily COVID-19 Vaccine Report, and will be updated on Tuesdays, with data through the prior Saturday, according to a spokesperson.

Previously, the DPH only provided data on the state’s breakthrough infections upon request. The Globe requested such data throughout July as breakthrough cases ticked up around the state, including hundreds stemming from the outbreak in Provincetown, where three-quarters of those infected were vaccinated.

Between July 10 and July 31, the total number of breakthrough cases in Massachusetts increased by almost 75 percent — from 4,450 to 7,737. Hospitalization and death among vaccinated individuals remained very low throughout those three weeks, increasing by just 92 and 21, respectively.


“This data makes clear that the vaccines are protecting virtually all residents from severe illness due to COVID-19, and that everyone should protect themselves and their families by getting vaccinated,” said a spokesperson for the Executive Office of Health and Human Services

Landrigan, of BC, said breakthrough infections tend to be “much, much milder than cases in unvaccinated people. Numerous vaccinated individuals who had breakthrough infections compared their symptoms to the common cold or seasonal flu — unpleasant, but not untenable.

“The most important thing to say about these cases is that there are almost no hospitalizations and almost no deaths — not quite zero, but almost zero,” Landrigan said. That’s compared to “significant” numbers of hospitalizations and deaths among the unvaccinated.

Landrigan also lauded the Department of Public Health for opting to regularly release data on the state’s breakthrough cases.

“Putting out more honest information is always better, because information empowers people,” he said. “It empowers the general public, it empowers the press, and it enables people to make informed decisions.”

At a national level, US Senator Ed Markey has urged the Centers for Disease Control and Prevention to “remain vigilant and transparent in its surveillance of breakthrough cases” by monitoring all breakthrough infections, not just those that result in hospitalization and death, as has been its policy since May 1.

In a letter to CDC Director Rochelle Walensky on July 22, Markey cited figures from Massachusetts. Between July 10 and July 16, there were over 700 breakthrough infections in the state — accounting for 43.4 percent of all new COVID-19 infections, he wrote.


“The American public must be informed of the continued risks posed by COVID-19 and its variants, and public health and medical officials, as well as health care providers, must have robust data and information to guide their decisions on public health measures,” Markey wrote.