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Forget what you thought you knew about catching COVID-19 more than once. SARS-CoV-2, the virus that causes COVID-19, keeps evolving – and so has information about your risk of being reinfected.

"Two years ago, we thought if you had COVID once that you would never get it again," said Dr. Preeti Malani, an infectious disease physician at the University of Michigan in Ann Arbor. But especially with the variants that have become dominant in the U.S. this summer, that thinking no longer holds.

When it emerged last November, the omicron variant of SARS-CoV-2 showed an ability to reinfect people who'd had earlier versions of the virus. This summer, according to the Centers for Disease Control and Prevention, the omicron subvariants BA.4 and BA.5 are , with BA.5 accounting for the majority of COVID cases. Both appear to be even more adept than other omicron subvariants at evading the body's defenses against infection.

Even having had an earlier version of omicron does not seem to protect against symptomatic infection from the BA.4 and BA.5 subvariants, Malani said. The subvariants also can infect vaccinated people.

"I have friends who have had COVID three times," said Malani, who has co-written an ongoing about the virus for JAMA. "One of my kids had it twice." And Malani herself recently tested positive for the first time, despite being up-to-date on her vaccinations.

The good news is that despite spreading more easily, the subvariants do not appear to cause more severe disease. And vaccination still protects against severe illness, especially hospitalizations and death.

But heart and stroke patients might need to step up their precautions.

Dr. Deepak L. Bhatt, executive director of interventional cardiovascular programs at Brigham and Women's Hospital in Boston, said it's hard to know exactly how a pandemic is unfolding in real time, and more research is needed on COVID-19 and the heart to provide definitive answers about the risks.

But conditions such as stroke, heart failure and coronary artery disease are among those that can lead to severe illness from COVID-19, the . And in the past month, Bhatt has seen "a number of patients" with severe cardiovascular, cardiopulmonary or neurological disease die from problems related to the coronavirus.

"It's not that they specifically died from COVID," said Bhatt, who is also a professor at Harvard Medical School. "But COVID tipped them over."

Some suggests what multiple bouts of COVID-19 might mean for heart and brain health. Researchers at Washington University School of Medicine in St. Louis, using data from the Department of Veterans Affairs, found that reinfection raised people's risks of cardiovascular and other complications when compared with people who had one infection. The risk grew with the number of infections.

The work has not been peer-reviewed, but Bhatt called its conclusions "believable" and said it made sense that with a major infection of any sort, getting infected a second time would mean more chances for problems.

The best protection against reinfection remains getting vaccinated and keeping up with boosters.

"There's still a lot of people that aren't vaccinated and were just thinking, 'Well, I'll get natural immunity, or I'll just wait it out,'" Bhatt said. "But those strategies won't work."

Vaccination helps even as the coronavirus evolves, Malani said. "It still protects against severe infection. And we shouldn't lose sight of that."

Updated vaccines tailored to omicron are expected to be available this year. Meanwhile, taking practical steps to avoid COVID-19 might be prudent, particularly for people who are traveling.

For Malani, a week ahead of a big vacation that required a negative COVID test, she urged her family to be cautious. "I said to everyone: 'Listen, I think we all need to be really extra careful. Because if one of us gets COVID, none of us are going on this trip.'"

Social connections are important, she said, but gatherings should be outdoors, or at least in well-ventilated areas. And people who are not feeling well should stay home.

The CDC says anyone who tests positive should stay home for at least five days and isolate from others. And while many guidelines about when to wear a mask have been relaxed, Bhatt encourages people to mask up in crowded indoor settings, "even if people around them aren't." Research shows it helps stop the virus's spread.

Malani acknowledged it can be confusing when advice shifts on something such as the risk of reinfection. "This isn't because the scientists and public health officials are asleep at the wheel," she said. It's what happens when experts learn more. So people should follow advice from reliable sources.

"The reason we care about this is because the vulnerable people can die, and our health care system can get overwhelmed with sick people," she said. "And we've seen that happen."

Editor's note: Because of the rapidly evolving events surrounding the coronavirus, the facts and advice presented in this story may have changed since publication. Visit Heart.org for the latest coverage, and check with the Centers for Disease Control and Prevention and local health officials for the most recent guidance.

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