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Experts say even a mild case of COVID-19 can develop into long COVID. Stefan Tomic/Getty Images
  • A new study reports that 75 percent of people with long COVID were not initially hospitalized.
  • Another study estimates that 1 in 5 people between ages 18 and 64 will develop post-COVID conditions with that percentage rising to 1 in 4 for people older than 65.
  • Another study also reports that vaccinations can help reduce the risk of developing long COVID.

About 75 percent of people experiencing long COVID were not hospitalized with their initial COVID-19 illness.

A new analysis suggests that even people with mild or moderate COVID-19 cases that didn’t require hospital admission can still develop long COVID.

“We know that people who get long COVID may have a severe infection, they may be hospitalized or may even have asymptomatic infections. So, it’s not surprising that so many people with long COVID have not been hospitalized, especially if you consider that the vast majority of people with COVID-19 are not hospitalized,” Dr. Dean Blumberg, chief of Pediatric Infectious Diseases at the University of California Davis, told Healthline.

The analysis used data from a registry of private healthcare claims from 78,525 people.

The participants were diagnosed with long COVID between October 2021 and January 2022. The analysis showed a difference between men and women. About 81 percent of the female subjects were not hospitalized compared with 67 percent of males.

Those ages 36 to 50 were most likely to receive a diagnosis of a post-COVID condition, with women being more likely than men.

The most commonly reported long COVID symptoms were abnormalities of breathing, cough and malaise, and fatigue.

The analysis comes as the U.S. Centers for Disease Control and Prevention released a study that found 1 in 5 people between ages 18 and 64 will develop post-COVID conditions, with that number rising to 1 in 4 for those older than 65.

The potentially serious conditions include respiratory conditions, kidney failure, cardiovascular conditions, blood clots, and neurological conditions.

Blumberg says the symptoms of long COVID can vary between people and may be influenced by the symptoms a person experienced in their initial COVID-19 illness.

“Some people have, for example, lung fibrosis, inflammation of the lung that results in decreased breath and oxygen capacity, and that’ll cause more fatigue,” he said. “And other people won’t have that, they’ll have other symptoms such as loss of taste and smell that’s prolonged. And then other people will have a brain fog, a real difficulty concentrating. So it really just depends on the manifestations that are occurring in each individual.”

A recent study based in the United Kingdom found that getting vaccinated after a COVID-19 positive test can reduce the risk of long COVID.

The researchers examined data about 28,000 people between ages 18 and 69 who were given at least one vaccination dose after they had tested positive for COVID-19.

The researchers found that long COVID symptoms were reported in 24 percent of people at least once during the follow-up period of seven months.

A first dose of COVID-19 vaccine was associated with a decrease of 13 percent in the risk of getting long COVID initially, while a second dose was associated with a further 9 percent decrease.

Dr. William Schaffner, an infectious disease expert at Vanderbilt University in Tennessee, says the results of the study are promising.

“We know that people who have recovered from COVID-19 and subsequently get vaccinated had very high levels of antibodies to the virus,” he told Healthline. “That’s a hopeful sign and encourages public health professionals to keep advocating for persuading people to be up to date in their vaccinations, whether or not they have had actual COVID-19 illness in the past.”

When it comes to avoiding long COVID, Schaffner says the best thing to do is avoid getting infected in the first place.

If a positive test does occur, he says it is important to take the time to properly recover.

“Try to prevent yet another infection from occurring, particularly if you’re a person who’s more apt to have serious disease. Keep wearing your mask, avoiding large groups, if at all possible,” Schaffner said.

“Paying attention to your illness, not trying to stretch yourself too much. Listen to your body, and do the degree of exercise and work that you know your body is capable of. But don’t go beyond that,” he added.