Compiling 15 different studies from around the world, the U.K.’s HSA wrote in a briefing released on Tuesday that not only do vaccines reduce the risk of getting the virus itself, individuals who were vaccinated with one or two doses were less at risk of developing long COVID compared with their unvaccinated counterparts. One study in the HSA briefing even found the chances of getting long COVID were halved for vaccinated people. 

There are currently no evidence-based treatment options for long COVID, with an estimated 2% of the U.K. population reporting post-COVID symptoms ranging from fatigue and shortness of breath to organ inflammation and behavioral changes, lasting for months on end. 

The 15 studies

Eight out of the 15 studies included in the briefing looked at whether vaccines protected against developing long-COVID symptoms, while the remainder studied the effects of a vaccine on someone who already has long COVID.

Of the first eight studies, six found that vaccinated individuals were less likely than unvaccinated people to develop medium- or long-term COVID symptoms. 

One of those studies, published in The Lancet, found that people who received two doses of the Pfizer, AstraZeneca, or Moderna vaccines or one single-dose Janssen vaccine were around half as likely as people who were unvaccinated, or only partially vaccinated, to develop long-COVID symptoms lasting more than 28 days.

But there may be an age caveat. One of the studies that health officials examined found vaccine effectiveness in combating post-COVID symptoms was highest in people age 60 or older, or age 19 to 35 years of age.

Dr. Mary Ramsay, head of immunization at the U.K. HSA, said in a government press release published on Wednesday that “vaccination is the best way to protect yourself from serious symptoms when you get infected and may also help to reduce the longer-term impact.”

Help for long haulers?

Three studies included in the HSA briefing compared long-COVID symptoms before and after vaccination and found that while some people reported an improvement of symptoms after vaccination, others still reported a worsening of symptoms.

“There is also evidence that unvaccinated people with long COVID who were subsequently vaccinated had, on average, reduced long-COVID symptoms (though some people reported worsened symptoms after vaccination),” the HSA briefing concluded. 

It is still unclear what causes long COVID, but some scientists think it may come from the remaining reservoirs of the virus in the body triggering ongoing inflammation. Akiko Iwasaki, professor of immunology at the Yale School of Medicine, said in the Guardian that remnants of SARS-CoV-2 have been discovered in almost every tissue from the brain to the kidneys in people affected by long COVID.

Deborah Dunn-Walters, chair of the British Society for Immunology’s COVID-19 task force and a professor of immunology at the University of Surrey, said in the Science Media Centre, a press office offering commentary on science news: “The immune system is thought to play a role in symptom development in a significant number of [long-COVID] cases, likely as a result of an over-reactive and/or slightly misdirected immune response during the acute COVID infection.”

More studies are needed on the HSA findings, said Dunn-Walters, but they give us insight into tackling long COVID and ”re-emphasize the importance of everyone, no matter their age, getting vaccinated against COVID-19.”