Mass. reports 4,608 new breakthrough cases this week

There were another 30 deaths among vaccinated individuals.

Samuel Zizi, of Mattapan, gets his first shot. (Photo by Pat Greenhouse/Globe Staff)

With widespread community transmission, breakthrough cases of COVID-19 continue to show up, as experts have predicted, but they’re much less likely to lead to hospitalization and death. So far only about 1.2% of vaccinated people have tested positive for COVID-19.

The state released updated data Tuesday on the number of COVID-19 cases, hospitalizations, and deaths among vaccinated individuals in Massachusetts. There have been a total of 58,807 breakthrough cases of COVID-19 as of Nov. 6, an increase of 4,608 from Oct. 30. Between Oct. 23 and 30, 3,192 breakthrough cases were reported, so about 1,400 more breakthrough cases were reported this week, a massive jump from last week, but case counts also increased.

There were 4,753,520 people vaccinated as of Nov. 6, meaning 1.2% have reported a breakthrough case of COVID-19. The rate has been steadily increasing — it was 0.23% on Aug. 7. 


“When we think about infections after vaccination, they’re relatively uncommon,” Dr. Sabrina Assoumou, an infectious disease physician at Boston Medical Center, told in October. “The numbers have been creeping up in Massachusetts but it’s close to 1% so we have to look at the big picture here and how common these are, and vaccination is a way to get us out of this mess.”

Though this reflects the overall trend of how many vaccinated people are reporting cases, it’s easier to understand on a week-by-week level. So, for example, how many of the new cases reported this week were breakthrough cases.

Between Oct. 31 and Nov. 6, 9,660 people tested positive for COVID-19, almost 1,900 more than the previous week, breaking a downward trend. The same week, 4,608 breakthrough cases were reported, meaning 47.7% of COVID-19 cases in that period were breakthrough infections, a significant jump from the previous week’s rate of 41%.

Assoumou referenced data published by the Centers for Disease Control and Prevention which shows that vaccinated people are six times less likely to test positive for COVID-19, and 11 times less likely to die from it, compared to those who are unvaccinated.


“These vaccines work remarkably well for protecting against hospitalization and death, but they’re not 100% effective,” she said “When we have high levels of community transmission of the virus it’s more likely we’ll get infections after vaccination. So, if we want to see less of these breakthrough cases, what we need to do is continue to vaccinate the unvaccinated.”

Hospitalizations and deaths are also increasing but at a much lower rate. Tuesday’s data showed a total of 1,940 hospitalizations and 468 deaths, an increase of 147 and 30 respectively from Oct. 30. Out of vaccinated individuals, 0.04% have been hospitalized and 0.01% have died. According to the data, 3.3% of breakthrough cases resulted in hospitalization and 0.8% in death — rates that have remained steady for weeks.

A spokesperson from the state Office of Health and Human Services told all available data continue to support that all three vaccines are highly protective against severe disease and death from all known variants of COVID-19. As of Oct. 9, the median age of those who died from a breakthrough case of COVID-19 was 81.2 years, and 73% had underlying conditions making them more likely to develop severe disease. Similarly, 61% of patients hospitalized with breakthrough infection had underlying conditions.


On Nov. 8, 35.2% of patients hospitalized for COVID-19 reported being vaccinated. With boosters approved for an ever-growing part of the population, and vaccination soon possible for 5- to 11-year-olds, leaders continue to emphasize the importance of getting vaccinated.


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