But what about long Covid?

MIT Medical answers your COVID-19 questions. Got a question about COVID-19? Send it to us at CovidQ@mit.edu, and we’ll do our best to provide an answer.

As pandemic restrictions ease, I’m wondering about long Covid. Up until now, reports of young, otherwise healthy people being debilitated by fatigue, brain fog, and memory problems after mild COVID-19 cases have made me very happy to keep wearing a mask. But I’m not hearing much about long Covid as mask mandates disappear. Is there a medical reason for that? I don’t want to be a hermit, but I also don’t want to be mentally or physically unable to participate in the MIT community because of a Covid case.

Scientists and clinicians have long known that certain acute viral or bacterial infections can have long-term consequences for a small number of individuals. A 1988 article in Critical Reviews in Neurobiology, for example, examined research related to “post-viral fatigue syndrome.” Other viral and bacterial infections have been known to cause damage to the heart or spinal cord.

Long Covid, which medical-type folks have started referring to as “post-acute sequelae of COVID-19” or PASC, likely represents some of the same biological mechanisms as these previously known aftereffects of other illnesses. It may affect a far higher percentage of recovered individuals, however — anywhere from 10–30 percent by some estimates — and could be a public health concern for years to come.

Long Covid is more than the usual fatigue that can last for a few weeks after recovering from an illness. According to the World Health Organization (WHO), symptoms of long Covid are present three months after an individual’s initial COVID-19 symptoms, last at least two months, and cannot be explained by an alternative diagnosis. People with long Covid may experience chronic exhaustion, shortness of breath, cardiovascular disease, and/or cognitive or neurologic symptoms ranging from “brain fog” and memory problems to sensory disturbances, depression, or even psychosis. While conventional lab tests rarely reveal abnormalities that would account for these symptoms, researchers using more sensitive measures have found evidence of anomalies in the immune systems, brains, lungs, and circulatory systems of individuals with long Covid.

You are not the only one with questions about your risk of long Covid. Even as the Omicron variant made “breakthrough infections” more common, most of us have felt generally well protected as vaccinated individuals in a highly vaccinated community. While a COVID-19 illness might be extremely unpleasant, we knew we were unlikely to end up hospitalized or worse. But the concern about long Covid remained. In some cases, the specter of ending up with a mysterious and debilitating chronic illness has become even more worrisome than the possibility of becoming infected with the virus itself.

Now a pair of recent preprint studies appear to show that vaccination is protective against long Covid as well.

Both groups of researchers — one in the UK, one in Israel — asked individuals who had recovered from a confirmed COVID-19 illness to report on symptoms they were experiencing more than 12 weeks after their initial diagnosis. They compared the responses of unvaccinated individuals with those who had received two doses of a COVID-19 vaccine at least two weeks before they became ill.

Both studies found that unvaccinated individuals were significantly more likely to report long Covid symptoms than individuals who became infected after receiving two doses of a vaccine. In the UK study, which matched vaccinated and unvaccinated groups on socio-demographic characteristics like age, sex, and place of residence, vaccination was associated with a “41 percent decrease in the odds of developing long Covid symptoms 12 weeks later, relative to not being vaccinated when infected.” In the Israeli study, individuals who had received two doses of the Pfizer mRNA vaccine were anywhere from 54 to 68 percent less likely than unvaccinated individuals to report any of the most commonly reported long Covid symptoms, despite being older and more likely to have pre-existing, chronic health conditions.

But the Israeli study went one step further. They also compared double-vaccinated individuals who had recovered from COVID-19 with a group of people who had never contracted the virus. After all, lots of people in the general population complain of fatigue, headaches, muscle pain, or difficulty concentrating — not just people who were previously ill with COVID-19. And this comparison was even more striking: Vaccinated individuals who had experienced breakthrough infections were no more likely to report any of these symptoms than individuals who had never been infected with the SARS-CoV-2 virus.

These results make sense to Medical Director Cecilia Stuopis, who notes that researchers have found evidence of genetic material from the virus in far-flung parts of the body many months after infection. “Symptoms of long Covid may be caused by inflammation in areas of the body that continue to harbor these viral remnants,” she explains. “But when a vaccinated individual is infected by the virus, it triggers an adaptive immune response. Specialized immune cells and antibodies quickly jump into action to attack and destroy the invader. In most cases, this means that the virus gets no further than the upper respiratory system before it is cleared from the body completely.”

Neither study included individuals likely to have been infected with the Omicron variant nor people who had received booster doses, but Stuopis doesn’t consider these caveats to be major shortcomings. “Omicron appears more likely than earlier variants to remain confined to the upper airways,” she notes. “And we can assume that boosted individuals would be even better protected against long Covid than those who had received only two doses of vaccine.”

Finally, Stuopis reminds you that masks remain a great option to protect yourself, even if they are not mandated. “You don’t need to choose between going maskless and being a hermit,” she says emphatically. “Many members of our community will choose to continue wearing masks in certain situations, and those choices will be respected. MIT will continue to make high-quality masks available on campus and encourage their use.”