Breakthrough COVID Cases in Massachusetts, Explained

At least 79 people have died and more than over 300 have been hospitalized in Massachusetts due to COVID-19 breakthrough cases after they were fully vaccinated, state health officials say.

What is a breakthrough COVID case, how common are they, and how are they being tracked? Here's what you should know.

A vaccine breakthrough case occurs when a person tests positive for COVID-19 after they've been fully vaccinated against the disease.

A person is considered “fully vaccinated” two weeks after receiving the second dose of either the Pfizer or Moderna COVID vaccine, or two weeks after receiving the single-dose Johnson & Johnson vaccine.

How many breakthrough COVID cases has Massachusetts had?

Public health officials have tracked 4,450 "breakthrough" cases of COVID-19 among Massachusetts residents fully vaccinated against the disease, representing about one-tenth of 1% of the roughly 4.2 million people immunized.

About 92% of the infections in vaccinated residents did not require hospitalizations, while 303 people, or 6.8%, were hospitalized, according to state Department of Public Health data through July 10.

The Boston Herald reported the breakthrough data last week based on a public records request.

Seventy-nine vaccinated residents in Massachusetts died from COVID-19, either without being hospitalized or following a hospital stay, DPH said. That death toll reflects 1.78% of the 4,450 confirmed breakthrough cases and 0.0019% of the 4,195,844 people fully vaccinated as of July 10.

“All available data continue to support that all 3 vaccines used in the US are highly protective against severe disease and death from all known variants of COVID-19. The best way to protect yourself and your loved ones is to get vaccinated,” the DPH said in a statement to The Boston Globe.

There has been a cluster of breakthrough coronavirus cases among vaccinated people in Provincetown.

How many total breakthrough cases have occurred in the US?

The CDC transitioned from monitoring all reported breakthrough cases to only reporting hospitalizations or deaths on May 1, the agency said.

That means the total number of breakthrough cases at this point is not made publicly available, but federal health officials did track all breakthrough cases from January of this year through April 30, 2021.

The CDC says that in that time period, a total of 10,262 breakthrough COVID cases were reported in 46 U.S. states and territories. About 63% of those cases were in women, with the median patient age at 58 years.

The CDC says 27% of those breakthrough infections were asymptomatic, while 2% died.

About 10% of those breakthrough cases were hospitalized, officials said, but among those hospitalized, 29% were asymptomatic or hospitalized for a reason other than COVID-19.

As the “hypertransmissable” Delta variant surges in communities across the U.S., CDC director Dr. Rochelle Walensky issued a stark warning to those who remain unvaccinated against the coronavirus, saying, “Our biggest concern is that we’re going to see preventable cases, hospitalizations and sadly, deaths among the unvaccinated.”

While breakthrough cases have been considered rare, they are possible and even "expected," per the CDC. Experts have said that while the vaccine itself cannot give you the virus, it is also not 100% effective at preventing the virus entirely, though those who receive the vaccine are far less likely to be hospitalized or die from it, data shows.

"COVID-19 vaccines are effective and are a critical tool to bring the pandemic under control," the CDC's website reads. "However, no vaccines are 100% effective at preventing illness in vaccinated people. There will be a small percentage of fully vaccinated people who still get sick, are hospitalized, or die from COVID-19."

The CDC says this is true of all vaccines: not one prevents illness 100% of the time.

Massachusetts health officials continue to urge those who have not gotten vaccinated yet to do so.

“Yes, the vaccines aren’t perfect. We expect that some folks will still be infected. But both in the studies and in real-life evidence they are awfully good,” Dr. Eric Rubin, an infectious disease physician at Brigham and Women's Hospital, told The Boston Globe last week.