Mass. reports 3,078 new breakthrough cases this week

There have been another 35 deaths among vaccinated individuals.

About 1% of vaccinated people have tested positive for COVID-19. Adam Glanzman/Bloomberg

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% 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 51,007 breakthrough cases of COVID-19 as of Oct. 23, an increase of 3,078 from Oct. 16. Between Oct. 9 and 16, 3,431 breakthrough cases were reported, so 353 fewer breakthrough cases were reported this week.

There were 4,711,614 people vaccinated as of Oct. 23, meaning 1.08% have reported a breakthrough case of COVID-19; it cracked 1% last week. 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 “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. 17 and 23, 7,922 people tested positive for COVID-19 (735 less than last week, continuing a downward trend). The same week, 3,078 breakthrough cases were reported, meaning 38.9% of COVID-19 cases in that period were breakthrough infections, a little lower than the previous week’s rate of 39.6%.

Assoumou referenced data recently 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 1,687 hospitalizations and 406 deaths, an increase of 121 and 35 respectively from Oct. 16. Out of vaccinated individuals, 0.04% have been hospitalized and 0.009% have died. According to the data, 3.31% of breakthrough cases resulted in hospitalization and 0.8% in death.

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.


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