It’s a question few people know the answer to, even after three years of the pandemic and more than 100 million Covid cases in the United States: When someone is infected today, what is their risk of developing long covid?
“Even the medical community isn’t clear on any of this. The data is emerging so quickly and the estimates are varied,” said Dr. Rainu Kaushal, chair of the department of population health sciences at Weill Cornell Medicine.
In the absence of definitive data on the long-term risk of Covid, seven researchers investigating the prevalence of the disease in the United States offered NBC News their best guesses. Most said it’s fair to assume the current risk for vaccinated people is 10% or less, and some thought the odds were smaller – 5% or less.
Even reinfections carry a prolonged Covid risk, they added.
“You can have a long Covid the second time, the third time. This reinfection is absolutely consecutive, and you pretty much do Russian roulette again,” said Dr. Ziyad Al-Aly, head of research and development at the veterans. Affairs St. Louis Health Care System and Clinical Epidemiologist at Washington University in St. Louis.
Since the start of the pandemic, nearly 38 million adults in the United States have reported post-Covid symptoms that have lasted three months or more, according to an NBC News analysis of data from a household survey conducted by the Census Bureau. Survey results showed that in February around 11% of adults who had had Covid before had long Covid.
These figures combine vaccinated and unvaccinated cases, although the risk profiles differ: Researchers interviewed estimated that for unvaccinated people, the risk of long Covid is around 15% to 20%.
The United States still sees more than 225,000 new Covid cases every week, according to the Centers for Disease Control and Prevention, as long as Covid is a pervasive threat.
“Out of 100 people you see, 95 or 96 people will be fine. But you might be one of those unlucky four, and I personally don’t want to take a chance,” Al-Aly said.
The risk of long Covid seems to be decreasing
Long Covid is most often defined as symptoms that last for at least three months after a coronavirus infection, although symptoms are wide ranging and vary in severity and duration. Many patients report fatigue, brain fog, shortness of breath, heart palpitations, and muscle, joint, or chest pain.
Overall, the rate of long Covid has declined since the Census Bureau began including questions about it in its household survey in June 2022. At that time, 19% of respondents who had had Covid have reported current symptoms that had lasted three months or more. .
But Sharon Saydah, a senior CDC epidemiologist who leads the agency’s post-Covid conditions team, said the survey is “not a good way to judge individual risk” given that it includes new long Covid cases and those that have lasted since earlier in the pandemic.
Experts have offered a few likely explanations for the downward trend in long Covid cases: the use of vaccines and treatments, and the nature of the omicron variant.
A series of studies have shown that even receiving a single shot of Covid lowers a person’s risk of long-term symptoms, and the risk further decreases with each additional shot. The antiviral Paxlovid also appears to reduce long-lasting Covid risks, according to a study awaiting peer review.
“We now have more things that can help lower your risk,” said Dr. Michael Gottlieb, an emergency physician and researcher at Rush University Medical Center.
Studies have also shown a drop in long-term Covid rates after the rise of the omicron variant, although researchers disagree on whether the variant itself is associated with fewer health problems. long-term health than its predecessors.
“Existing data suggests that the risk of long Covid in the post-omicron era may be less, but it is confounded by the increase in vaccination rates occurring over essentially the same period,” said Dr Stuart Katz , principal investigator at the National Institutes of Health’s RECOVER initiative, which studies the long-term effects of Covid.
Factors that influence a person’s risk of long Covid include their age, gender, medical history and the severity of their illness. According to a review in the journal Nature, women and people with type 2 diabetes or ADHD may be at high risk.
Kaushal said she saw persistent heart and kidney problems in older men who had severe Covid, as well as trouble sleeping and shortness of breath in younger women.
New long-lasting Covid cases could become less severe, on average
There is some hope that new cases of long Covid will be milder than those that developed earlier in the pandemic, due to the same factors driving rates down.
“The incidence, severity and duration seem to be decreasing,” Kaushal said.
Dr. Sun Yoo, director of the outpatient Covid monitoring program at UCLA Health, said she still sees debilitating cases of long Covid, but “generally I see fewer of them and milder versions.”
Katz noted, however, that the large number of omicron infections may partly explain why doctors are seeing more patients with milder symptoms.
And some vaccinated people still face lingering, life-altering health issues after contracting Covid.
“I see these patients – some of them literally can’t even read an email. They have such deep brain fog that it significantly impairs their cognitive abilities,” Al-Aly said.
Studies give range of long Covid rates
Quantifying the risk of long Covid is difficult for many reasons, and Saydah said it’s also difficult to compare rates to other post-viral illnesses because other viruses haven’t caused this level of illness. widespread over a short period.
Long Covid studies have defined the condition distinctly and assessed different types of patients.
“Everyone comes up with different approaches,” said Dr. Roy Perlis, who directs the Center for Quantitative Health at Massachusetts General Hospital. “There’s the health records approach. There’s the survey approach. … All of these tell us different things. None of them are perfect.”
One of the largest studies on the subject, from the Al-Aly team in St. Louis, suggested that the overall risk of long Covid was 4% to 7% in the first year of the pandemic. .
“My hunch now is it’s lower than that,” he said.
This study looked at the health records of more than 181,000 VA patients who contracted Covid through March 2021, then compared that group to nearly 4.4 million veterans who weren’t tested. positive.
But relying on health records can lead to underestimates because such studies only include patients who sought medical care and were tested for Covid.
To account for this, Yoo and his team at UCLA directly observed more than 1,000 Covid patients who were at high risk of severe illness or hospitalized in the first year of the pandemic. Their study found that 30% had symptoms that persisted for up to 90 days after their diagnosis or discharge from hospital.
She speculated that the overall risk for people vaccinated today could be around 5-10%.
Kaushal, too, said “common sense is that we are closer to 5%”.
Saydah said those estimates “seem reasonable” given CDC data, which pegs the rate of long Covid at 20% from March 2020 to November 2021. Now, she explained, “studies show that vaccination reduces your risk by 20% to 50%.”
The RECOVER Initiative’s observational study recruited more than 18,000 people, so it may eventually yield clearer estimates of long-Covid risk, according to Katz. Interim results expected later this year could also shed light on the most common symptoms of the disease.