People fully vaccinated against Covid-19 are nearly 50% less likely to develop long Covid from a breakthrough infection than unvaccinated people, according to a recent study published in The Lancet Infectious Diseases.

Recovery clinics for Covid-19 long-haulers

Study details and key findings

For the study, researchers analyzed data submitted by more than 1.2 million adults in the United Kingdom through the Covid Symptom Study phone app from December 2020 to early July 2021, which includes a period of time in which the delta variant was dominant in the country.

Three vaccines have been authorized in the U.K.—the Pfizer-BioNTech vaccine, the Moderna vaccine, and the Oxford-AstraZeneca vaccine—all of which are two-dose regimens.

Of the almost 1 million fully vaccinated people in the study, just 0.2% reported a breakthrough infection. Those who reported a breakthrough infection were around twice as likely to have an asymptomatic case of Covid-19 as those who were unvaccinated and infected. And those experiencing breakthrough infections were 73% less likely to be hospitalized than the unvaccinated.

The researchers also found that the fully vaccinated were 49% less likely to experience long-term symptoms lasting at least four weeks post-infection than the unvaccinated.

However, the study's authors acknowledged the limitations of this research, which include self-reported data and the fact that long Covid has wide-ranging symptoms that vary in severity. Additionally, while the researchers analyzed data over a period that included the delta variant, the study did not distinguish the risk of long Covid after a breakthrough infection by variant.

Building upon prior research

The study's findings are similar to a smaller study from Israel in July that found that 19% of the 39 fully vaccinated health care workers who got breakthrough infections still had symptoms six weeks later.

But at the time, there was little early research on how often breakthrough infections lead to long Covid, and the authors of the study cautioned that the sample size of breakthrough infections was small. The study also looked at data from before the delta variant became dominant in the country.

"This is really, I think, the first study showing that long Covid is reduced by double vaccination, and it's reduced significantly," Claire Steves, a geriatrician at King's College London and lead author of the Lancet study, said.

"We don't have a treatment yet for long Covid," Steves added, but getting vaccinated "is a prevention strategy that everybody can engage in."

Long Covid turning into chronic fatigue for many patients

Meanwhile, another new study has found that many patients with long Covid are struggling with chronic fatigue, MedPage Today reports.

Of the 239 individuals who were in online support groups for long Covid, 85% said they still had severe fatigue when they were surveyed 11 weeks after the onset of their symptoms, according to Maarten Van Herck, a PhD student at the University of Hasselt in the Netherlands, who recently spoke at the virtual annual meeting of the European Respiratory Society.

By week 24, the proportion of individuals reporting severe fatigue was 79%, and the majority of them had consulted at least one medical professional and at least one specialist without benefit. Only 4% of those with severe fatigue at week 11 and 13% at week 24 had received formal rehabilitation therapy.

"A large share [of long Covid patients] is progressing toward chronic fatigue," Van Herck said, adding that "it remains unclear whether and to what extent fatigue will resolve spontaneously" moving forward.

The study found that around 11% of the participants reported overall poor health at week 24, down from 26% in week 11. However, more than 25% of the participants at week 24 rated their health status as an average of 56 on a 100-point visual analog scale, and their responses to a quality of life survey put them in less than the fifth percentile compared to the general population.

Notably, there are limitations associated with this self-reported data, particularly as it was drawn from online support groups, which may not be representative of all long COVID patients, MedPage Today reports. (Joseph, STAT News, 9/1; Anthes, New York Times, 9/1; Gever, MedPage Today, 9/7)