It’s a question few people know how to answer, even after three years of the pandemic and more than 100 million cases of Covid in the US: When someone gets infected today, what is the risk of developing long covid?
“Even the medical community is unclear about all of this. The data is emerging so quickly and estimates vary,” said Dr. Rainu Kaushal, chair of the division of population health sciences at Weill Cornell Medicine.
In the absence of definitive data on the long-term risk of Covid, seven researchers who have investigated the prevalence of the condition in the US offered NBC News their best guesses. Most said it was fair to assume the current risk to vaccinated people was 10% or less, and some thought the odds were lower – 5% or lower.
Even reinfections carry a risk of long-term Covid, they added.
“You can get long Covid the second time, the third time. This re-infection is absolutely consequential and you’re pretty much playing Russian roulette again,” said Dr. Ziyad Al-Aly, head of research and development at Veterans Affairs St. Louis Health Care System and a clinical epidemiologist at Washington University in St. Louis.
Since the start of the pandemic, nearly 38 million U.S. adults have reported post-coronavirus symptoms lasting three months or more, according to an NBC News analysis of Census Bureau household survey data. The survey results showed that as of February, about 11% of adults who had ever had Covid had long-term Covid.
These figures combine vaccinated and unvaccinated cases together, although the risk profiles differ: The researchers interviewed estimated that for unvaccinated people, the risk for long-term Covid is about 15% to 20%.
The US continues to record more than 225,000 new cases of Covid each week, according to the Centers for Disease Control and Prevention, so long that Covid is an ever-present 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 that chance,” Al-Aly said.
The risk of long-term Covid appears to be shrinking
Long-term Covid is most often defined as symptoms lasting at least three months after being infected with the coronavirus, although symptoms are wide-ranging and vary in severity and duration. Many patients report fatigue, brain fog, shortness of breath, palpitations, and muscle, joint, or chest pain.
Overall, the rate of long-term Covid has been declining since the Census Bureau began including questions about it in its June 2022 household survey. At that time, 19% of respondents who had Covid reported current symptoms that had lasted three months or more.
But Sharon Saydah, a senior epidemiologist at the CDC who leads the agency’s post-Covid conditions team, said the survey is “not a good way to judge individual risk” since it includes new long-term Covid cases and those that have last from earlier. in the pandemic.
Experts offered a few possible explanations for the downward trend in long-term Covid cases: vaccine and treatment uptake and the nature of the omicron variant.
A number of studies have shown that even getting a single Covid vaccine reduces a person’s chances of long-term symptoms, and that the risk decreases further with each additional vaccine. The antiviral Paxlovid also appears to reduce the chances of long-term Covid, according to a study awaiting peer review.
“Now we have more things that can help you reduce 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 micron variant, although researchers disagree on whether the variant itself is associated with fewer long-term health problems than its predecessors.
“Existing data suggest that the risk of long-term Covid in the post-micron era may be lower, but it is confounded by the increase in vaccination rates occurring over essentially the same time period,” said Dr. Stuart Katz, principal investigator with the RECOVER initiative at National Institute of Health, which studies the long-term effects of Covid.
Factors that affect a person’s risk of long-term Covid include age, gender, health 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 increased risk.
Kaushal said she sees persistent heart and kidney problems in older men who have had severe Covid, as well as sleep disorders and shortness of breath in younger women.
New long-term Covid cases may become less severe, on average
There is some hope that new cases of long-term Covid are milder than those that developed earlier in the pandemic, due to the same factors causing rates to decline.
“Its frequency, severity and duration seem to be decreasing,” Kaushal said.
Dr. Sun Yoo, director of the Ambulatory Covid Surveillance Program at UCLA Health, said she still sees debilitating cases of long-term Covid, but “in general, I see less of it and less severe versions of it.”
Katz noted, however, that the sheer number of microbe infections may partly explain why doctors are seeing more patients with milder symptoms.
And some vaccinees still face persistent, life-changing health problems after the onset of Covid.
“I see these patients — some of them literally can’t even read an email. They have brain fog that’s so deep, it significantly reduces their cognitive abilities,” Al-Aly said.
Studies give a range of long term Covid rates
Quantifying the risk of long-term Covid is difficult for many reasons, and Saydah said it is also difficult to compare rates with other post-viral diseases, as other viruses have not caused this level of widespread disease in a short period of time.
Long-term studies of Covid have defined the condition in different ways and evaluated different types of patients.
“Everyone has 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 research approach. . . . They all tell us different things. None of them are perfect.”
One of the largest studies on the subject, by Al-Aly’s team in St. Louis, showed that the overall risk of long-term Covid was 4% to 7% during the first year of the pandemic.
“My hunch now is that 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 and then compared that group with nearly 4.4 million veterans who did not test positive.
However, relying on health records can lead to underestimations, as such studies only include patients who have sought medical care and been tested for Covid.
To explain this, Yoo and her team at UCLA directly observed more than 1,000 Covid patients who were at high risk of severe illness or were hospitalized during the first year of the pandemic. Their study found that 30% had lingering symptoms up to 90 days after diagnosis or hospital discharge.
He speculated that the overall risk for vaccinated people today could be about 5% to 10%.
Kaushal, too, said that “the gut feeling is that we are closer to 5%.
Saydah said those estimates “seem reasonable” given CDC data, which puts the rate of long-term Covid at 20% from March 2020 to November 2021. Now, she explained, “studies show that vaccination reduces 20% to 50% risk.”
The RECOVER initiative’s observational study has enrolled more than 18,000 people, so it could eventually provide clearer estimates of long-term Covid risk, according to Katz. Interim findings expected later this year may also shed light on more common symptoms of the condition.