Understanding Long Covid

We know more now than before, and it’s still alarming

Dr. Tom Frieden
9 min readDec 19, 2022
A young woman sitting on a bed holds her hands to her temples as if in pain.
Photo Credit: Resolve to Save Lives

Author Note: This piece is written largely based on and because of the extensive research conducted by Andrew Gall and the Prevent Epidemics team at Resolve to Save Lives.

I raised the risks of long Covid back in July 2020, and in July 2022 highlighted the difficult battle many people — often called “long-haulers” — continue to experience months and even years after a SARS-CoV-2 infection. Many long-haulers continue to speak out, raising awareness and advocating for better understanding and treatment of this chronic illness, including actress Alyssa Milano, the NHL’s Brandon Sutter, Clemson defensive end Justin Foster, and Senator Tim Kaine of Virginia. Now, almost three years into the pandemic, we have more information about what causes long Covid, its clusters of symptoms, how to prevent it, who is most at risk — but still far too little to offer those who are struggling.

What is long Covid?

A person is considered to have long Covid — sometimes called Post-Acute Sequelae of SARS-CoV-2 Infection (PASC) or Post Covid-19 Condition (PCC) — if 12 weeks after being infected they continue to have symptoms or develop new symptoms that can’t be explained by an alternative diagnosis. Long Covid is a term that covers multiple symptoms, conditions, and complications thought to occur after or because of a Covid infection.

The SARS-CoV-2 virus can damage blood vessels throughout the body. This is often seen in the form of blood clots, inflammation, and stiffened arteries. Covid also appears to damage nerves, linger in organ tissues, and impair the immune system, making people vulnerable to other viruses and bacteria either already in their bodies or that they encounter later on. This is why people experiencing long Covid report symptoms in so many areas of the body, including the brain, lungs, heart, reproductive organs, kidneys, and legs.

What are the impacts of long Covid?

Physical exhaustion, “brain fog,” and shortness of breath are the three most common symptoms of long Covid, but far from the only ones. A study involving 3,672 patients from the United States, Canada, the UK, and the EU found 203 symptoms unique to long Covid, often appearing in clusters. Symptoms tend to cluster based on sequence of onset and by age group — for example, stomach issues for those under 21 and neurological disturbances for those aged 21–45 — but every age group is affected and none is immune.

One particularly concerning symptom is called Post-Exertional Malaise (PEM). According to that same study, 89% of long Covid patients experienced disabling physical exhaustion or brain fog after minor physical or mental exertion. 68% of those who experienced PEM said that their symptoms lasted for days, hindering their ability to go to work or otherwise return to life as normal.

In addition to this array of symptoms, evidence points to long-term and life-threatening complications caused by long Covid related to the heart, brain and other organs, and the immune system. One disabling manifestation with increasingly clear documentation of relation to SARS-CoV-2 infection is Postural Orthostatic Tachycardia Syndrome (POTS), with patients becoming lightheaded with low blood pressure and rapid pulse when they stand up.

Who’s at risk?

Anyone can get long Covid — including people who are young, healthy, or who initially had a mild or even asymptomatic infection. Resolve to Save Lives, the organization I lead, launched a campaign called “Voices of Long Covid” that features the heart-wrenching stories of three young long-haulers.

Although no one is free from the risk of long Covid, research has revealed that some people are more likely to develop severe symptoms and complications — including people who are medically vulnerable, unvaccinated or who experienced a severe infection that required hospitalization. Those who are older tend to have more pre-infection comorbidities that place them at higher risk in general, as do people who have high BMI, sedentary lifestyle, or history of smoking and drinking.

Many of the socio-economic factors that increase risk for getting infected with Covid — such as low socioeconomic status and lack of access to healthcare — also appear to increase risk of developing long Covid. Being a health care worker or essential worker may increase risk for developing long Covid due to the increased risk of exposure to Covid positive individuals.

Risk might differ between men and women. One study found women to be 1.22x more likely to develop long Covid and experience a wider range of symptoms, including ears-nose-throat, respiratory, musculoskeletal, gastrointestinal, and neurological. Men, though at lower risk than women overall, were found to be at higher risk of developing end-stage kidney disease, heart damage, and diabetes.

Different hypotheses for this include hormonal differences between men and women, naturally increased immune responses among women of reproductive age that dysregulate after a Covid infection, and because long Covid is an autoimmune disorder, a type of illness which tends to be more common in women. It could also be that more women seek care for long Covid symptoms than men.

A large study from the U.S. Department of Veteran Affairs found that the risk for developing long Covid and other complications increases each time someone gets Covid. Though the cohort of veterans is not demographically representative of the overall U.S. population, it does coincide with increasing evidence that organ damage from SARS-CoV-2 infection can be cumulative, meaning that re-infection may also be a risk factor. Until we know more, it’s best to avoid getting reinfected with Covid to the extent possible, even for people who have successfully recovered from a past infection and have no lingering symptoms.

How common is long Covid?

There remains a wide range of estimates of how likely a Covid infection is to cause long-term symptoms. Some analyses suggest that the rate is as low as 1% for those with an uncomplicated Covid infection, and as high as one third or more of those who were hospitalized for Covid. Because Covid infection is so common — approximately two-thirds of people in the United States have been infected at least once — even a low rate of long Covid following infection translates into a large number of people suffering.

CDC estimates that 1 in 7 adults in the U.S. have experienced long Covid symptoms at some point since the pandemic began (signifying incidence), and 1 in 14 adults are currently experiencing long Covid (signifying prevalence) — a quarter of whom experience significant activity limitations. This survey suggests that long Covid is twice as common in females as in males, and is most prevalent among Hispanics and White, Non-Hispanic people.

Studies from Scotland and China indicate that recovery from long Covid can be slow and partial. After 18–24 months, half of long Covid patients report being fully recovered, 30–40% of patients report partial recovery, while approximately 10–20% report no recovery and even experience new-onset of symptoms.

Ongoing research

Several ongoing studies are dedicated to demystifying long Covid and supporting those experiencing long-term health impacts. RECOVER, an initiative created by the National Institutes of Health (NIH), is recruiting for studies in several cities across the United States. The Centers for Disease Control and Prevention (CDC) is leading the Innovative Support for Patients with SARS-CoV-2 Infections (INSPIRE) Study to better understand long-term health effects. And the United Nations and WHO have partnered with Long COVID Europe, a clearinghouse for information and resources. This August 2022 article in Health Affairs offers detailed information about studies and federal resource and support programs.

So, what can we do?

If you think you have long Covid, it’s important to seek support. This can be from your primary care doctor as well as other resources, such as a long Covid clinic. A list of long Covid clinics around the country can be found here. A gradual resumption of activities, to the extent possible, has been better tolerated than attempts to quickly resume full activities, which can result in setbacks.

Stay up-to-date with Covid vaccination. Not only does this help reduce the chance of Covid infection, it also reduces the risk of developing long Covid if you do get Covid, and can help reduce the severity of long Covid symptoms. Because the virus has adapted and vaccine protection against infection wanes over time, people may be susceptible to infection if it’s been 4–6 months since their last shot, or since a recovery from Covid.

A bivalent booster, which targets both the original SARS-CoV-2 strain and the Omicron variant, can help restore some of that protection. A literature review posted this month suggests that the booster provides even people who have previously been infected with Covid or who are currently experiencing long Covid symptoms with a low but statistically significant decrease in post-Covid symptoms for the variants circulating between December 2019 and April 2022 — which includes both Delta and Omicron.

Paxlovid reduces severity of Covid in those who are older or medically vulnerable, and could also reduce the risk of long Covid, though more research is needed. CDC recently released an MMWR report about Paxlovid and how it helps decrease hospitalizations for older adults with mild-to-moderate Covid. Another study found that chances of getting a clot in one of the large veins in your leg, called a deep vein thrombosis (DVT), is reduced by 70%, and developing long Covid is reduced by 26% when treated with Paxlovid.

Paxlovid helps whether you’re vaccinated or not. However, results are best if Paxlovid is given within the first 5 days of diagnosis. Some people who take Paxlovid will rebound and the Covid infection will return. This happens most often in those with underlying medical conditions but should be considered possible for anyone who takes the medication. This may mean staying home or masking for several more days after feeling better or testing negative, and close monitoring for several more weeks after that. Importantly, even those who do not take Paxlovid can have long infection courses or can rebound: There is clear evidence that those who are at high risk — the elderly and those who are medically vulnerable — definitely benefit from Paxlovid, despite the risk of rebound.

Testing is another strategy to help prevent the spread of infection to family, friends, and the community. Home tests can be helpful, and if a test comes back positive it is extremely likely that person has Covid. If two tests taken 24 hours apart come back negative, the person is probably not infectious. Home tests are widely available in the United States, sold in many grocery stores and drugstore pharmacies. The White House announced last week that you can order another round of free rapid, at-home tests this winter.

Masking works very well to prevent a person with Covid from spreading it, as well as to prevent the wearer from catching it from someone else. The more concerned people are about their risk of getting Covid, the better their mask game should be. CDC created a helpful graphic that describes how different masks stack up. An N95 is most effective at preventing infection, with KN95s being the next best option. Both are better than a surgical mask or a cloth mask, which are better than nothing.

Graphic showing the odds of a positive Covid test based on no mask, cloth mask (56% reduction), surgical (66%) and N95 or KN95 (83%).
Photo Credit: CDC

Because Covid is a respiratory virus spread predominantly in the air, masking when around lots of people, especially indoors, is important. Monitoring Covid spread in your area will help determine how likely you are to encounter it. We at Resolve to Save Lives partnered with The New York Times to produce an interactive online guide to help people understand and navigate their Covid risk across the United States. You can continue to receive up-to-date information here.

Improved Ventilation is also key to reducing Covid transmission. Proper ventilation with outside air can help reduce indoor concentrations of airborne contaminants, including viruses. This can be as simple as opening windows if the weather permits, or as complex as addressing air flow and installing HEPA filters.


Ultimately, the safest bet is to do our best to avoid getting Covid. You can’t get long Covid if you don’t get Covid. And although we know more now than we did last year, there is still a lot we don’t know. No age group is completely protected from long Covid, some people are more at risk than others, and long Covid can be debilitating even for young people who were otherwise fit or healthy. Each of us must assess the risk we face from Covid and take steps to avoid infection based on what activities we’re comfortable with and how hard Covid is raining where we are. And whether it’s Covid or not, if you’re sick stay home. The only thing we should spread is holiday cheer.



Dr. Tom Frieden

President and CEO, Resolve to Save Lives | Former CDC Director and NYC Health Commissioner | Focused on saving lives. twitter.com/drtomfrieden