According to the Centers for Disease Control and Prevention (CDC)Trusted Source, long COVID is a condition in which COVID-19-related health issues last 4 weeks or more after contracting the virus that causes the disease.
Even those who did not have COVID-19 symptoms immediately after contracting SARS-CoV-2 can develop long COVID. Symptoms may last for several weeks or months.
Research suggests that at least 54%Trusted Source of those who develop COVID-19 experience long COVID. According to a 2021 meta-analysisTrusted Source, the most common outcomes and symptoms among those with long COVID include:
- chest imaging abnormalities for 62.2% of people
- general functional impairments for 44%
- fatigue or muscle weakness for 37.5%
- general pain for 32.4%
- generalized anxiety disorder for 29.6%
- sleep disorders for 27%
- difficulty concentrating for 23.8%
Other symptoms include:
- brain fog
- headache
- skin rashes
- fever
- changes to the sense of smell or taste
- diarrhea
Research is emerging on risk factors for long COVID. To help parse through these studies, MNT has summarized some of the main findings so far. We also spoke with three experts on the best ways to mitigate the risk factors for long COVID.
Risk factors
One studyTrusted Source that followed 309 participants for 2–3 months after contracting SARS-CoV-2 identified four factors that increase a person’s risk of long COVID:
- a higher viral load
- the presence of certain autoantibodies that mistakenly attack the body’s own tissues
- reactivation of the Epstein-Barr virus (EBV)
- having type 2 diabetes
However, the study authors noted that their research might not be conclusive as they could not confirm causation, and their sample size makes it difficult to establish any specific predictors.
Nevertheless, other studies support their findings. One studyTrusted Source found that SARS-CoV-2 may reactivate EBV and, in turn, lead to long COVID symptoms. Around 95%Trusted Source of the world’s population carries this virus, although EBV largely lays dormant and is asymptomatic.
Another study found that older age, being female, and having preexisting health conditions were also linked to long COVID.
“Clinical risk factors are largely related to the severity of illness, duration of hospitalization, age at the time of infection, and preexisting comorbidities, such as lung disease, asthma, diabetes, etc.,” Prof. Elizabeta Mukaetova-Ladinska, a professor of psychiatry of old age at the University of Leicester in the United Kingdom, told Medical News Today.
“Thus, the severity of the SARS-CoV-2 infection can increase the risk for long COVID by nearly fourfold, preexisting lung disease and asthma increase the likelihood [by] six- [and] nearly 10-fold, respectively, whereas age increases the risk by 67%,” she added.
“In addition, female sex and age under 50 years are now also acknowledged as risk factorsTrusted Source for long COVID. The latter is of importance, since [there] appears to be some overlap of symptoms of long COVID with those of perimenopause and menopause,” she explained.
Prof. Mukaetova-Ladinska further explained that lower levels of immunoglobulin (Ig) antibodies IgM and IgG3Trusted Source, when combined with clinical risk factors, may also increase a person’s risk of developing long COVID.
She also said that researchTrusted Source suggests a link between alterations to the gut microbiome and long COVID: “Namely, COVID-19 patients with healthy gut bacteria and a microbiome similar to [that of a healthy person] appear to be less likely to develop long COVID, whereas those COVID patients who develop long COVID have a less diverse and abundant microbiome.”
Vaccination
When asked about likely risk factors for long COVID, Dr. Donald J. Alcendor, an adjunct associate professor of pathology, microbiology, and immunology at Vanderbilt University School of Medicine, told MNT that “[t]he most important risk factor for long COVID is being unvaccinated, getting a primary COVID-19 infection, and having [one or more] underlying health [conditions].”
“Studies show that getting the vaccine will greatly reduce your risk of developing long COVID. It was also shown that being vaccinated with only one dose of the COVID-19 vaccine even after being diagnosed could reduce your risk of developing long COVID.”
– Dr. Donald J. Alcendor
“Finally, people who received at least one dose of any of the three COVID-19 vaccines — Pfizer-BioNTech, Moderna, and Johnson & Johnson — before diagnosis were 7–10 times less likely to have two or more long COVID symptoms compared to unvaccinated people,” he added.
While the study Dr. Alcendor cited has not yet undergone peer review, other research published in peer-reviewed journals supports these claims.
For example, one study published in The Lancet: Infectious Diseases in January 2022 found that two-dose vaccination approximately halved the odds of experiencing COVID-19 symptoms for 28 days or more after the initial illness.
Dr. Alcendor also warned about the risk to children: “We must remember that children — although [this is] rare — can develop long COVID, and individuals who have breakthrough [or] post-immune infections or asymptomatic COVID infections can also develop long COVID. Some individuals who developed long COVID have recovered after being vaccinated.”
A press release from the U.K. Health Security Agency supports his comments. The release highlights a recent review of 15 studies, suggesting that those who have received vaccinations are less likely to experience long COVID than unvaccinated individuals.
