• Health
  • COVID-19

You Can Still Get Long COVID If You’re Vaccinated and Boosted

4 minute read

COVID-19 vaccines were designed primarily to prevent severe disease and death—two purposes for which they continue to work very well. But when the shots first rolled out, many people also hoped they would block or even reverse symptoms of Long COVID, such as fatigue, cognitive dysfunction, chronic pain, and neurological issues.

By now, it’s clear that even people who are fully vaccinated and boosted can get Long COVID, and recent research suggests that vaccines aren’t the Long COVID shields people wished for.

Studies have come to very different estimates about the degree of protection vaccines offer against Long COVID. But some of the latest findings point to fairly disappointing protection. In one July report from the U.K.’s Office for National Statistics, more than 4% of vaccinated and boosted adults in the U.K. who were infected by Delta, Omicron BA.1, or BA.2 still had symptoms at least 12 weeks later. A preprint posted online on Sept. 6 (which has not yet been peer-reviewed) suggests the situation isn’t any better in the U.S. Researchers surveyed people from June into July, as the BA.5 variant was taking over. Among those who said they’d had COVID-19 at least a month earlier, roughly 20% had symptoms that lasted at least four weeks, with little difference between vaccinated and unvaccinated people.

That’s not to say vaccines are useless against Long COVID. A research review published in eClinical Medicine in August analyzed a mix of peer-reviewed and preprint studies, six of which looked at whether people who were vaccinated before they got infected had a lower chance of developing Long COVID than unvaccinated people who got sick. All six studies concluded that vaccinated people are at lower risk.

Read More: Should You Mix and Match Omicron Boosters? Here’s What to Know

At first, it appeared that vaccines were pretty protective against Long COVID. Some 2021 research suggested vaccinated people were up to 50% less likely to develop Long COVID after a breakthrough infection, compared to unvaccinated people who got COVID-19. But a large study published in Nature Medicine in May reached a less-encouraging conclusion: it found that vaccinated people were only about 15% less likely to develop Long COVID than their unvaccinated counterparts.

Studies have reached a wide range of estimates because of differences in how they were designed, how long they tracked people, and how they defined Long COVID, says Dr. Ziyad Al-Aly, chief of research and development at the Veterans Affairs St. Louis Health Care System, a clinical epidemiologist at Washington University in St. Louis, and a co-author of the Nature Medicine study. But regardless of the exact numbers, “the common thread is vaccines do offer some protection, but it’s never complete,” he says. “It’s partial.”

That makes sense, Al-Aly explains. The shots weren’t designed with chronic symptoms in mind, but rather to reduce the severity of acute disease, which offers some secondary benefits for Long COVID prevention. Though anyone can develop the condition, people who have severe initial cases of COVID-19 are at highest risk—so the fact that vaccines tend to keep cases milder hopefully means fewer people will develop lasting complications.

Early in vaccine distribution, some anecdotal reports also sparked hope that the shots could improve symptoms among people who already had Long COVID. But it’s still not clear whether that’s true. The authors of the eClinical Medicine research review couldn’t find a strong consensus in the 11 studies they analyzed on this topic: seven found that Long COVID patients’ symptoms improved after vaccination, while four found that they stayed the same or worsened. In rare cases, people have also reported developing Long COVID-like symptoms after getting vaccinated, even if they hadn’t knowingly had the virus.

The new Omicron-specific boosters only raise more questions about vaccination and Long COVID, Al-Aly notes, since researchers haven’t had a chance to study them yet. In the future, he says he hopes researchers will develop vaccines that provide longer-lasting protection against all variants, block viral transmission, and prevent Long COVID. Some of these efforts are underway, as scientists work to develop nasal vaccines that could reduce the risk of infection and shots that could target many different coronaviruses at once.

For now, though, even vaccinated, boosted, and previously infected people aren’t immune to Long COVID. Any infection could lead to lingering complications, which underscores the importance of limiting exposure to the virus as much as possible.

More Must-Reads from TIME

Write to Jamie Ducharme at jamie.ducharme@time.com