Paxlovid might help shorten and diminish a COVID infection, but the antiviral doesn’t reduce the risk of developing long COVID, a new study shows.

About 16% of COVID patients treated with Paxlovid wound up with long COVID symptoms, compared to 14% of those not given the oral medication, researchers found.

“Our finding that Paxlovid treatment during acute infection is not associated with lower odds of long COVID surprised us, but it is consistent with two other rigorously conducted studies finding no difference in post-COVID conditions between 4 and 6 months after infection,” said lead author Dr. Matthew Durstenfeld, an assistant professor of medicine at the University of California, San Francisco.

Paxlovid is recommended for treating people at high risk for severe COVID infection, to ease symptoms and keep them out of the hospital.

But there’s been some debate regarding whether the drug could prevent long COVID, in which symptoms caused by the initial infection can last for weeks, months or even years.

For this study, Durstenfeld and his colleagues followed up on COVID patients treated between March and August 2022, to see if they had developed long COVID.

Not only did Paxlovid not prevent long COVID, but the researchers found those who took the drug went on to have as many long COVID symptoms as those who didn’t.

The most common long COVID symptoms included fatigue, shortness of breath, confusion, headache and altered taste and smell.

A small percentage of people went on to develop severe long COVID, and again those who received Paxlovid were just as likely as those who didn’t to have long-term severe symptoms.

Researchers also found that more people than expected experienced a “rebound” after taking Paxlovid, with their COVID infection roaring back after it had appeared to go away.

About 21% of people who improved while taking Paxlovid wound up reporting rebound symptoms, and about 26% re-tested positive for COVID after testing negative and completing their treatment.

However, this rebound didn’t appear to make patients more inclined to develop long COVID. About 11% of rebound patients reported long COVID symptoms, compared with 8% of those who didn’t rebound.

“We found a higher proportion with clinical rebound than previously reported, but did not identify an effect of post-treatment rebound on long COVID symptoms,” Durstenfeld said in a university news release.

The new study was published Jan. 4 in the Journal of Medical Virology.