Study: Vaccination After COVID May Reduce Long COVID Risk

There is overwhelming evidence that COVID-19 vaccines are extremely effective at reducing the risk of hospitalization and death from the disease. However, much remains to be understood about the mechanism of long COVID and how it responds to vaccines.

The authors of a new study published in the BMJ went over the data of more than 28,000 participants from the COVID-19 Infection Survey to observe if there are any associations between COVID-19 vaccination and the likelihood of long COVID symptoms. They found that getting vaccinated after contracting COVID-19 lessens the odds of developing long COVID, at least in the first few months after vaccination.

The study only had a median follow-up of 141 days from the first vaccination and 67 days from the second one, meaning further research and a longer follow-up are needed to conclusively establish a cause-and-effect connection.

How Does the Vaccine Reduce Long COVID Risk?

The study found that the odds of developing long COVID symptoms that persisted for at least 12 weeks decreased by around 12.8% after getting one dose of a COVID-19 vaccine. Getting a second vaccine dose is associated with a further 8.8% decrease in long COVID risk.

“At this time, it is not clear what the mechanism of long COVID is, nor of why the vaccine might reduce risk,” Priya Duggal, PhD, epidemiologist at the Johns Hopkins Bloomberg School of Public Health and co-lead of the Johns Hopkins COVID Long Study, told Verywell. “However, if the vaccine increases antibody levels in those previously infected—as a booster—it may help to eliminate any residual viral particles, or potentially viral reservoirs.”

It’s possible that getting vaccinated may also reduce the symptoms of unvaccinated individuals who already have long COVID.

Some patients with long COVID experience immune system malfunctions following a COVID infection, and the COVID vaccine may “reset” the immune response to behave in a more functional way, Mark Loafman, MD, MPH, family physician at Cook County Health, told Verywell.

According to the study authors, more studies are needed to understand the biological mechanisms of long COVID risk or symptom improvement after vaccination.

“There appears to be a persistent level of viral antigen in some patients with long COVID. This can trigger symptoms from an autoimmune antibody response to that viral antigen,” Loafman, who was not associated with the study, said. “The antibody generated by the vaccine helps clear the viral antigen, helping reduce the autoimmune antibody symptoms.” 

Can Boosters Minimize Long COVID Risk Among Fully Vaccinated Individuals? 

The BMJ study focused on unvaccinated populations and the impact of COVID-19 vaccines after infection, which raises the question of whether booster doses can minimize long COVID risk for fully vaccinated people as well.

“This is something that people have considered,” Duggal said. “It would be important for us to look at this in available data, if there is a reduction in symptoms after a booster.” Ideally, people who got infected after one or two vaccine doses—but before their third or fourth dose—would be observed, she added.

Presumably, booster shots may reduce long COVID risk among fully vaccinated people in the same way that initial vaccine doses minimize risk on unvaccinated individuals, Loafman said. In fact, several large studies suggest this is the case.

It’s normal for antibody levels to fall significantly after a few months of vaccination, and the body preserves the memory (or ability) to make more antibodies if or when a new exposure occurs. However, it takes days to weeks for that to occur, and the virus can replicate to a larger degree during that time, he added.

“A booster dose quickly raises the antibody levels back up to a level that severely limits the virus's ability to replicate, which also decreases the inflammatory response,” Loafman said. “All these factors mean fewer symptoms.”

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