(CNN) — People who are vaccinated or who take Paxlovid during a Covid-19 infection have a lower risk of developing long Covid, new research shows.

The US Centers for Disease Control and Prevention defines long Covid as new, returning or ongoing health issues more than four weeks after an initial infection. According to the CDC, 1 in 5 Covid-19 survivors ages 18 to 64 and 1 in 4 survivors 65 or older have an ongoing health issue that might be attributable to Covid-19 infection.

A study published Thursday in JAMA Internal Medicine analyzed data from 41 studies, including more 860,000 people around the world. Of the four studies with vaccination information of nearly 250,000 people, those who had been vaccinated against Covid-19 had almost half the risk of long Covid than people who weren’t vaccinated.

“These findings are important because they enable us to better understand who may develop long Covid and also advocate for the benefit of vaccination,” said Dr. Eleana Ntatsaki, a rheumatologist at Ipswich Hospital in England and co-author of the study.

Dr. Linda Geng, co-director of Stanford University’s Post-Acute Covid-19 Syndrome Clinic, says the findings are encouraging and add to mounting evidence that vaccines can reduce the risk of long Covid.

“That is probably one of the best tools that we have, to get vaccinated to help reduce severe acute illness but helping hopefully also to prevent and protect against developing long Covid,” said Geng, who was not involved in the research.

Women, people who smoke, those who are overweight and adults over 40 are more likely to have long Covid, the study found.

Hospitalization during a Covid-19 infection as well as underlying health problems including asthma, COPD, diabetes, coronary heart disease, a weakened immune system, anxiety and depression are also associated with increased risk of the condition.

Previous research has found that long Covid is associated with nearly twice the risk of heart and lung problems or death.

The study authors say these findings will help providers better understand long Covid and serve those living with the condition.

“We can have a better strategy for optimizing any modifiable risk factors, with public health promotion campaigns, encouraging smoking cessation, vaccination and healthy weight management in the target population,” Ntatsaki said.

Another study published Thursday in JAMA Internal Medicine found that using the antiviral medication Paxlovid within five days of a positive Covid-19 test was associated with a lower risk of long Covid in all age groups, regardless of vaccination status or history of infection.

Paxlovid was linked with a 26% lower risk of long Covid, a 47% lower risk of death and a 24% lower risk of hospitalization 30 days after an initial infection.

“This is really a sizable risk reduction that we think is important,” said Dr. Ziyad Al-Aly, chief of research and development at the VA St. Louis Health Care System and co-author of the study.

Al-Aly notes that the study included only people taking Paxlovid under its emergency use authorization, which includes adults over 60 or those who have an underlying medical condition, so the findings do not apply to everyone.

However, the findings support the use of Paxlovid use in high-risk people, as much focus has been on preventing hospitalization and death during the initial infection, Al-Aly says.

“When thinking about whether to use Paxlovid or not, we should be thinking about effectiveness in the acute phase but also effectiveness in reducing the long-term complications from Covid infection.”

Experts hope the research encourages further studies on prevention and management of long Covid, as there is currently no specific treatment for the condition.

“I do want to remind everybody that, for example, in our own clinical practice, we still see people who are having long Covid despite having been vaccinated and despite having antiviral therapy during acute Covid. So, while these might be promising and help reduce risk, it doesn’t take it away completely,” Geng said. “There’s currently really no guarantee against long Covid except to not get Covid.”

Vaccination, Paxlovid decrease risk of long Covid, studies show