Vaccination Dramatically Lowers Long Covid Risk [View all]

At least 200 million people worldwide have struggled with long COVID: a slew of symptoms that can persist for months or even years after an infection with SARS-CoV-2, the virus that causes COVID. But research suggests that that number would likely be much higher if not for vaccines.

A growing consensus is emerging that receiving multiple doses of the COVID vaccine before an initial infection can dramatically reduce the risk of long-term symptoms. Although the studies disagree on the exact amount of protection, they show a clear trend: the more shots in your arm before your first bout with COVID, the less likely you are to get long COVID. One meta-analysis of 24 studies published in October, for example, found that people who’d had three doses of the COVID vaccine were 68.7 percent less likely to develop long COVID compared with those who were unvaccinated. “This is really impressive,” says Alexandre Marra, a medical researcher at the Albert Einstein Israelite Hospital in Brazil and the lead author of the study. “Booster doses make a difference in long COVID.”

It is also a welcome departure from earlier studies, which suggested that vaccines provided only a modest defense against long COVID. In 2022 Marra’s team published a meta-analysis of six studies that found that a single dose of the COVID vaccine reduced the likelihood of long COVID by 30 percent. Now, that protection appears to be much greater.

A study published in November in the BMJ found that a single COVID vaccine dose reduced the risk of long COVID by 21 percent, two doses reduced it by 59 percent and three or more doses reduced it by 73 percent. Vaccine effectiveness clearly climbed with each successive dose. “I was surprised that we saw such a clear dose response,” says Fredrik Nyberg, an epidemiologist at the University of Gothenburg in Sweden and one of the co-authors of the study. “The more doses you had in your body before your first infection, the better.” That lines up with the findings of several new studies, which similarly show this ladderlike benefit. Marra’s October 2023 meta-analysis found that two doses reduced long COVID likelihood by 36.9 percent and three doses reduced it by 68.7 percent. And in a study published last year in the Journal of the American Medical Association, other researchers found that the prevalence of long COVID in health care workers dropped from 41.8 percent in unvaccinated participants to 30 percent in those with a single dose, 17.4 percent with two doses and 16 percent with three doses.

https://www.scientificamerican.com/article/vaccination-dramatically-lowers-long-covid-risk/