I’m vaccinated. Should I be worried about all these breakthrough infections?
Not too worried. Some amount of breakthrough infections were anticipated.
“You expect this,” said Dr. Shira Doron, an infectious diseases doctor and hospital epidemiologist at Tufts Medical Center. “Did I expect something as big as the Provincetown cluster? No, I didn’t expect something that widespread.”
“We know that vaccines are not 100 percent effective. No vaccine is 100 percent effective,” agreed Dr. Daniel Kuritzkes, the chief of infectious diseases at Brigham and Women’s Hospital. “The more infection that is circulating in a community, the greater the likelihood that people who are vaccinated are going to have breakthrough infections.”
In clinical trials, the approved vaccines had variable efficacy rates — Pfizer-BioNTech at 95 percent, Moderna at 94.1 percent, and Johnson & Johnson at 72 percent.
But they were tested at a time when “there was a lull in the numbers of infections in the United States,” which means that those rates were “the best-case scenario,” said Kuritzkes.
The clinical trials were also “conducted in a very different setting,” when most individuals were wearing masks, distancing, and staying home — another reason the efficacy rates might be lower now that most people have resumed their pre-pandemic lives, explained Doron.
Delta has also become the predominant variant in the United States, and it tends to be associated with a higher viral load, she said. “It’s going to make a little bit more likely for it to overcome people’s vaccine-induced or natural immunity.”
It’s important to remember that the vaccine is working. The Department of Public Health said last week that 0.1 percent of people in Massachusetts who have been vaccinated against the coronavirus have contracted COVID-19.
Vaccination also almost always prevents those who are infected from contracting a severe case of COVID-19 that requires hospitalization or results in death. If a vaccinated individual is infected, “the overwhelming likelihood is that they will have a mild upper respiratory infection, maybe something that resembles a flu, and not need hospitalization,” Doron said.
I have plans to vacation on the Cape. Should I cancel them?
“I don’t think people need to avoid traveling to the Cape,” Kuritzkes said. “I do you think that people should be more cautious.”
Vaccinated individuals should still wear a mask indoors, and avoid indoor venues where they won’t be able to keep a mask on, like bars and restaurants. “Those are situations where you really could see a significant spread of infection,” Kuritzkes said.
Dr. David Hamer, an infectious diseases doctor at Boston Medical Center, also recommended “indoor mask use with an effective mask whenever possible, even for people who are fully vaccinated.” Vacationers should also try to stay outside as much as possible, particularly when they are eating or drinking, he said.
Still, there are numerous activities — like going to the beach, playing golf or tennis, and riding bikes — that “should pose no risk and do not require mask use unless in a crowded, poorly ventilated location,” said Hamer.
Dr. Philip Landrigan, the director of the Global Public Health Program at Boston College, advised tourists to “use your situational awareness to determine where you’re going to go and how you’re going to behave when you get there.”
“The Cape’s a big place, and there’s lots and lots of venues down there, from very crowded night spots in Provincetown to empty beaches,” Landrigan said. “I hope people do go to the Cape. I hope they do get some time away. … But take precautions.”
Vacationers should also be sure to adhere to public health measures in their destinations. Provincetown issued an advisory on Monday that advised even vaccinated individuals to wear masks indoors — a step that all the experts lauded.
I was on the Cape earlier this month. What steps should I take?
Health officials in Boston have urged anyone who visited Provincetown since July 1 to test themselves for COVID-19, and self isolate until they receive a negative result. Doron echoed that guidance.
Hamer noted that some vaccinated people have chocked their mild symptoms up to seasonal allergies, but urged anyone who has been to the Cape and is experiencing discomfort to get a test.
“If they have any mild symptoms — runny nose, nasal congestion, sore throat, low grade fever, dry cough — they should definitely consider being tested,” he said. “Even if they think it might be seasonal allergies, it could be something more than that.”
Anyone who suspects they might have been exposed in Cape Cod or elsewhere should also avoid contact with vulnerable individuals.
“If a person has been in a place like a nightclub or a bar where there’s a high risk of infection, they have to be extraordinarily conscientious about not going into a hospital or nursing home in the next two weeks because the risk is high that they could be the person who infects a number of vulnerable older people or sick people,” Landrigan said.
I live in Boston. Should I be concerned that the outbreak will spread?
So far, at least 35 cases of COVID-19 in Bostonians have been traced back to Provincetown.
“Provincetown is only 120 miles from Boston by road and it’s only two hours on the fast ferry, and lots of people go back and forth all the time, especially in the summer. If there are cases in Provincetown, it’s certainly going to spread to Boston. It’s inevitable,” Landrigan said.
Kuritzkes agreed that the regular back-and-forth between Boston and the Cape could result in an uptick of cases in Boston.
Landrigan recommended that individuals take precautions in crowded environments, and be extra cautious in venues with lots of young adults, since there’s been rapid virus transmission in that demographic.
Hamer said that he wears a mask indoors in Boston and Cambridge — not just due to the surge on the Cape, but to a rise in cases across Massachusetts.
“We had over 300 cases yesterday. It had dipped down the less than 100 per day for a while a couple of months ago, and it seems to be creeping up,” he said. “I’m worried.”
Kuritizkes also reminded individuals to be aware of who is in their household, and to keep in mind those who are unvaccinated or otherwise vulnerable to COVID-19, like the immunocompromised.
All experts said that vaccination remains the single most important step to protect oneself and others. “Anything else you want to do is your own personal choice at this point,” Doron said.
The situation on Cape Cod is “reminder that this that this pandemic is not over,” Landrigan said. “It’s still bubbling around in the population. There are still people who are infected, there are still people who are shedding the virus.”
And despite the fact that Massachusetts leads the nation in vaccinations, experts said that it’s still not enough.
“We can’t be satisfied that we’ve got something like 70 percent of the population vaccinated here in the Commonwealth,” Kuritzkes said. “We really need to get to as close to 100 percent as we can and work to see the rest of the United States vaccinated if we want to go back to having tourism and travel and commerce.”
Camille Caldera can be reached at camille.caldera@globe.com.