‘Should I start returning to normal?’ Experts still advise caution for those recovering from Omicron.

Ryan Gagnon (left) raised a glass at Phoenix Landing in Central Square. Gagnon said he’s unsure how much he should go out after recovering from COVID.Josh Reynolds for The Boston Globe

Despite all his caution, dutifully getting his shots and limiting his socializing, Ryan Gagnon still wound up getting COVID around the holidays, as did hundreds of thousands of other people in Massachusetts.

Now mostly on the mend, the Quincy resident is venturing out again, albeit somewhat cautiously. And, with an immune system charged up with antibodies from his infection, Gagnon questions how much he should limit going out.

”I’ve already gotten this thing. It’s already held me back,” he said. “Should I start returning to normal?”

That question is likely on the minds of a lot of people: More than 300,000 vaccinated Massachusetts residents got breakthrough infections during the height of the Omicron surge, possibly more because of the wider use of at-home tests that do not automatically report positive results to the state.

So, has a huge class of “super immune” people risen among us, and could they help hasten the return to normal? In fact, scientists say that vaccinated people who have also recently recovered from a natural infection have among the highest degrees of protection, including increased defenses to future variants.

“It’s not so much ‘super immunity,’ but adequate immunity,” said Dr. Duane Wesemann, an immunologist at Brigham and Women’s Hospital. “It highlights how beautiful the adaptive immune system is. It’s not perfect. It does what it does and has been evolving to do . . . provide protection.”

But unfortunately, as with so much of the science around the coronavirus, it’s still not clear just how much of this dearly acquired immune protection is enough to ward off future infection, or whether the virus might mutate in ways that evade even bolstered immunity

Several studies provide clues to how durable this protection is, depending on whether the immunity came from the vaccines, an infection, or a combination of the two. Importantly, there are two types of immune responses that scientists are watching: those from B cells, which create antibodies, and those from T cells, which work to kill infected cells and alert other white blood cells to respond.

A study led by Wesemann and published in December 2020 that looked at antibody response after vaccination, and separately, after infection, found robust levels at the outset that declined over time and plateaued, lessening their ability to prevent future cases of COVID.

But another review that Wesemann also led, posted online in preprint form in September, found a stronger response among those who had gotten infected and then got vaccinated afterward. Their antibodies decayed at a slower rate over seven months compared to those who had been vaccinated without a prior infection. Their antibodies also had a better ability to recognize variants.

Yet a third study, recently published in the journal Science Immunology, found a similar phenomenon, including among those who got infected after first being vaccinated. The researchers, led by a team at Oregon Health & Science University, found that people with breakthrough cases, as well as those infected before they were vaccinated, generated antibodies at least 10 times more potent than those who received vaccinations alone.

While antibodies decay over weeks, the immune system’s memory B cells and T cells offer a robust backup to serious illness, and have already shown an adaptability to future variants. T cells and B cells that have encountered viruses are said to have “immune memory” because the cells offer more durable protection.

“There has not been a lot of focus on immune memory, yet that is critically important for any vaccine,” said Dan Barouch, professor of medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and co-lead of the vaccine research working group Massachusetts Consortium on Pathogen Readiness. “It’s maybe the most important thing to know how the vaccine protects six to 12 months after the vaccine.”

In a recent study published in Nature, led by Barouch, researchers looked at individuals eight months after they had been given two doses of Pfizer or one shot of Johnson & Johnson. It found their T cells were responsive to Omicron despite its mutations, and despite declining antibody levels. In a preprint paper also led by Barouch, which looked at individuals who experienced breakthrough infections in Provincetown, T cell responses also spiked following an infection in vaccinated people.

But here, too, it’s less clear how long the protection from antibodies or T cells lasts. Barouch said people who have been vaccinated and had a breakthrough infection still need to be cautious.

“We’re dealing with a pandemic that is unclear and uncertain, and people should adhere to public heath guidelines regardless,” he said.

Dr. Rajesh Gandhi, an infectious disease physician at Massachusetts General Hospital, also said there is a lot of variability among those who got infected, including the severity of their illness and the strength of their immune response, further clouding how long someone can expect to be protected.

Gandhi is still advising his patients to get a booster shot, even those who were vaccinated in the first round and experienced a breakthrough infection.

“If you had prior infection or vaccination, in general, the vaccinations are translating to milder disease, less hospitalization and death,” Gandhi said, noting exceptions for the elderly and those who are immunocompromised.

At the very least, people who have likely been infected with Omicron have substantial protection from Omicron, Wesemann said. If another variant circulates that looks similar to Omicron, the immune response may be robust. Early indications are that the latest variant, BA.2, might have a genetic sequence that closely resembles Omicron. However, future mutations may be a different story altogether.

“For Omicron, it’s like there is a weird magic it has. It goes in between our immune system and gets us,” Wesemann said. “But the vaccine-induced T cells and antibody cells are making it better. It’s not obvious to us when sick how sicker we could have been without them.”

Even some with these higher levels of protection can’t seem to shake some anxiety as they resume normal activities. Meaghan Hilton, from Lakeville, ventured to an indoor water park with her children and husband in January after they all recovered from COVID. Yet being among the crowd felt scary, even though the infection came after she and her husband were vaccinated and boosted, she said.

“You start thinking, what if? What if we didn’t get it bad enough?” Hilton said.

Marlishia Aho, of Boston, who has also been vaccinated and boosted, said she is open to bringing her toddler to the Children’s Museum or playdates now that her entire family had COVID in January. Yet she is still wearing masks and limiting indoor activities.

“I may be more open to taking him to indoor places now that he’s gotten COVID,” she said. “But I recognize that it’s still a pandemic and we still want to reduce risk.”