A clue to this extraordinary possibility comes from tens of thousands of responses to US Census Bureau questionnaires, which show a declining percentage of COVID survivors reporting prolonged COVID symptoms. Survivors of COVID.
Last June, the Census Bureau, in partnership with the National Center for Health Statistics, added questions about the long-running COVID-19 “Household Pulse Survey,” a mostly monthly online survey that began in April 2020 to assess the impact of the pandemic.
The study defines long-term COVID as symptoms that last at least three months after being infected with the coronavirus. About 200 symptoms have been identified, the most common of which are deep fatigue, palpitations, neurological complications, and indigestion.
An average of 58,794 COVID survivors nationwide responded to each of the nine long-form COVID surveys offered by the Census Bureau to date. The Chronicle’s analysis revealed a significant trend: in each study, a steadily smaller number of people reported long-term symptoms of COVID.
In June, 18.9% of respondents said they were “currently” experiencing a long-term illness with COVID. By the end of the year, it had dropped to 11.3 percent and by February to 10.8 percent.
In California, the percentage of people reporting current symptoms rose slightly in July and October, but otherwise mirrored the national trend, falling from 16.2 percent in June to 10.3 percent in February.
“Brilliant,” said Dr. Steven Deeks, a longtime COVID researcher at UCSF who is not involved in the research. “These trends appear to be consistent with our and other anecdotal experiences.”
Research shows that people can have long-lasting COVID, whether their initial infection was severe or mild. Researchers point to three probable causes: pieces of the virus remaining hidden in the body, continuous inflammation caused by the coronavirus, and autoimmunity – when the body’s own immune system is activated. These, in turn, can wreak havoc on the body months or even years later.
But is the “virus’s ability to cause prolonged COVID-19” waning? asked Deeks. “That’s really the question posed by this data.”
It is possible that the results of the survey indicate that some people are recovering from a long period of COVID. A large Israeli study published in January found that most COVID patients with mild infections saw their lingering symptoms disappear within a year of getting sick.
Deeks and two other long-term COVID experts at Stanford University and UC Davis said the apparent decline in long-term COVID may be due to vaccinations and the evolution of the coronavirus variants that cause COVID.
Dr. Christian Sandrock, who co-founded the long-term COVID clinic at UC Davis, said he has seen a decrease in long-term COVID referrals to the clinic.
One reason, he said, could be the omicron and its progeny. “Just as omikron has more cold symptoms and fewer serious illnesses and hospitalizations” than earlier variants, it also appears to produce fewer long-term symptoms, he said.
A new study by Swiss researchers, to be presented at the European Congress of Clinical Microbiology and Infectious Diseases in April, found that people infected with the omicron variant were less likely to report prolonged COVID symptoms than people infected with the original delta strain. These findings support the results of previous studies suggesting that omicron is less likely to cause long-term COVID-19 than previous variants.
Sandrock also acknowledged the COVID vaccine.
For example, a recent study published in the British Medical Journal found that the COVID vaccine reduces the likelihood, severity, and duration of a long-term illness with COVID.
Dr. Linda Geng, director of Stanford Medicine’s long-standing COVID clinic, agreed that vaccines and newer variants may be responsible for the results of the census study.
However, he said self-reported data, such as census surveys, have limitations because people may define prolonged COVID differently.
Geng said he continues to see a lot of new patients at his long-running COVID clinic.
“Even if the number is lower, the overall magnitude of the problem could still be significant if high numbers of infections persist,” he said. “The only guarantee against long-term COVID is that you won’t get COVID.”
According to federal data, US coronavirus cases have dropped by 40% in the past month. But still around 170,000 people get the disease every week.
And among those still suffering from prolonged COVID, there is tremendous frustration with the lack of viable treatments.
Some evidence has emerged that Paxlovid, an oral antiviral drug used to treat COVID-19, may help reduce the risk of long-term illness with COVID.
A November study of 56,000 COVID patients found that more than 9,000 who took Paxlovid within the first five days of infection had a 25% lower risk of long-term COVID symptoms. But the data from one study is inconclusive.
In a webinar last month, the White House’s director of the COVID-19 response, Dr. Ashish Jha, told Bob Wachter, UCSF’s chief medical officer, that the data showing that treatments like Paxlovide can reduce the risk of long-term COVID disease are “very illustrative.”
“I wouldn’t bet on it,” he said, although he noted that “clinically it makes sense.”
Stanford researchers hope for clearer evidence. They are looking for candidates for a clinical trial to see if Paxlovid can treat long-term COVID when people already have it.
Reach Aidin Vaziri: avaziri@sfchronicle.com; Nanette Asimov: nasimov@sfchronicle.com, Twitter: @NanetteAsimov