How does reinfection impact long COVID? Here’s what we know so far.

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"There are some patients that we’ve been following for a year or a year and a half that have not recovered. And that’s where we need more research on therapeutic options for them,” said Dr. Luis Ostrosky, chief of infectious diseases at UTHealth Houston and Memorial Hermann Hospital. (Getty Images)

Experts are urging caution as Americans gather indoors in the late fall and winter months, with COVID-19 cases already on the rise ahead of the Thanksgiving holiday.

Now that most people in the U.S. have been infected at least once with COVID-19, some complacency may be setting in; but even if another round of SARS-CoV-2 infection may start to feel old hat, experts warn that the possibility of long COVID is still a threat Americans should be wary of — even if they’ve managed to avoid long COVID in the past.

What is long COVID?

There is no single agreed-upon definition of long COVID, or any agreed-upon method for defining and diagnosing it.

The Centers for Disease Control and Prevention reported in June that nearly 1 in 5 Americans who had COVID-19 still have symptoms of long COVID, which the CDC defines as symptoms lasting more than three months post-infection that were not present earlier. Long COVID symptoms vary — from respiratory and heart symptoms, to neurological symptoms, to general ailments such as fatigue or muscle aches — and the CDC says that while long COVID is more common in people who suffered a severe bout of COVID-19, even people who experienced mild or asymptomatic cases can suffer from “post-COVID conditions.”

Dr. Luis Ostrosky-Zeichner, chief of infectious diseases at UTHealth Houston and Memorial Hermann Hospital, said there are three types of patients he sees at the hospital’s long COVID clinic: people with lingering damage from a severe case of COVID-19; people with underlying illnesses that were exacerbated by COVID-19; and “what we think of as 'true' long COVID patients, that have multiple symptoms for which we cannot currently find an objective cause.”

Ostrosky said the good news is that most of the last category of long COVID patients improve on their own within four to six months.

“But there are some patients that we’ve been following for a year or a year and a half that have not recovered. And that’s where we need more research on therapeutic options for them,” he said.

What happens if you already have long COVID and get infected with COVID-19 again?

For those battling long COVID, Ostrosky said getting another infection can be a huge blow.

“It’s pretty devastating,” Ostrosky said of some patients he has seen with long COVID who get reinfected with SARS-CoV-2. “They may have been making a lot of headway with this four- to six-month recovery process, and then it’s a huge setback for them. Very demoralizing, very disheartening for them when this happens.”

More research is still needed on how reinfection impacts those already suffering from long COVID, but self-reported cases can provide some insight. In a recent online survey conducted in the United Kingdom, 80% of those who described themselves as still having long COVID symptoms reported that another case of COVID-19 exacerbated their symptoms.

Of those who were in recovery or remission from long COVID, reinfection recurred in about 60% of individuals; of those individuals, 40% said that the second bout of long COVID was just as severe as the first time, 32% said it was less severe and 28% said it was more severe.

“It’s a pretty broad range of experience in terms of the severity of the second bout of long COVID,” Dr. Jessica Justman, an associate professor of epidemiology at Columbia University, who was not involved in the survey, told Yahoo News. “The bottom line was: If you have or previously had long COVID, getting an infection again could make you feel your long COVID has gotten worse or come back. So it’s an additional reason to get vaccinated and take steps to minimize your exposures.”

If you haven’t had long COVID before, how might a second (or third or fourth) COVID-19 infection affect your chances of developing it?

A COVID-19 test with two red bands, indicating an infection.
A recent study using data from the Department of Veterans Affairs’ national health care database found that reinfection increased the risk of long COVID as well as other adverse health outcomes. (Getty Images)

The CDC says that symptoms from reinfection are likely to be less severe than the first infection, but that “some people can experience more severe COVID-19 during reinfection,” and that the assortment of variants circulating may mean that an individual may not have as much immunity from a previous infection as is typically the case.

So even if you didn’t get long COVID the first time, it’s still possible to develop long COVID if you get reinfected with the virus.

“Past performance doesn’t predict future performance. You might have had a really mild case before, but you don’t have anything assured whether the next case is going to be as mild or if it's going to be more severe,” Ostrosky said.

“There’s also so much we don’t know about what kind of damage accumulates with repeat infections. So don’t let your guard down.”

A study published last week using data from the Department of Veterans Affairs’ national health care database found that reinfection increased the risk of long COVID, as well as other adverse health outcomes, including a twofold increased risk of death and a threefold increased risk of hospitalization compared to those who were not reinfected.

“Without ambiguity, our research showed that getting an infection a second, third or fourth time contributes to additional health risks in the acute phase, meaning the first 30 days after infection, and in the months beyond, meaning the long COVID phase,” senior author Dr. Ziyad Al-Aly, a clinical epidemiologist at the Washington University School of Medicine said in a press release.

The study found that reinfection compounded risks of long COVID regardless of whether participants were unvaccinated, vaccinated or boosted. In general, though, the impact of vaccination status on long COVID outcomes is still murky. Another study by the same authors found that those who received the COVID vaccine were only 15% less likely to develop long COVID than those who were unvaccinated, but the CDC says that people who aren’t vaccinated may be at higher risk of developing “post-COVID conditions” than those who are vaccinated. Other studies have shown that those who received two doses of the COVID vaccine cut their risk of developing long COVID in half.

“For people that feel that ‘I’m not going to die from COVID, it’s OK to get multiple infections,’ this should really be an eye-opening study that shows us that there’s still a lot to learn about the long-term consequences of multiple episodes of this infection,” Ostrosky said.

Justman pointed out that while the study provides additional reasons to take extra care and stay up to date on vaccinations, the retrospective nature of the study means that some outcomes could have been missed. Because data on the participants was collected retroactively instead of following them in real time, the study might have missed some participants who were reinfected with SARS-CoV-2 but were asymptomatic, or who tested positive for a mild case and didn’t seek treatment. If such cases had been properly counted, Justman said, that may have decreased the risks posed by reinfection.

“They did see [what’s known as] a dose-response relationship,” Justman said. “Individuals who had three COVID infections had a higher risk of these outcomes than people who had two infections, and those with two infections had a higher risk than people who had just one. And whenever you see that kind of dose-response relationship, it tells you that what you’re looking at might be real.”

What happens next?

"It’s still important to take advantage of all the vaccines that you can possibly avail of, i.e. flu vaccine, COVID boosters. And if you’re in a crowded indoor place, think very carefully about your COVID exposure, and try to see if you can wear a mask if at all possible," Dr. Jessica Justman, an associate professor of epidemiology at Columbia University said. (Getty Images)
"It’s still important to take advantage of all the vaccines that you can possibly avail of, i.e. flu vaccine, COVID boosters. And if you’re in a crowded indoor place, think very carefully about your COVID exposure, and try to see if you can wear a mask if at all possible," Dr. Jessica Justman, an associate professor of epidemiology at Columbia University said. (Getty Images)

While information on long COVID and reinfection — and long COVID in general — is limited, a number of studies are underway that could soon offer some answers. The National Institutes of Health is working on a study called Researching COVID to Enhance Recovery (RECOVER) to learn more about the long-term effects of COVID-19. The CDC is also conducting a number of studies with partners, including with Nova Southeastern University for a project called "COVID-19: Understanding the Post-Viral Phase (COVID-UPP)," on patients who continue to have symptoms more than three months after infection.

“There’s going to be lots of information coming out, so it’s kind of a ‘Watch this space,’” Justman said. “It’s definitely a work in progress, but I think what we’ve learned so far would reinforce those same messages that everybody in public health keeps repeating over and over — which it feels like the public maybe doesn’t want to hear it anymore. It’s still important to take advantage of all the vaccines that you can possibly avail [yourself] of, i.e. flu vaccine, COVID boosters. And if you’re in a crowded indoor place, think very carefully about your COVID exposure, and try to see if you can wear a mask if at all possible.”