Introduction
Recent studies suggest that the rates of “long COVID” may be declining. Although these studies were not designed to assess the cause of this trend, scientists suspect that the decrease is a result of increased immunity against the SARS-CoV-2 virus (the virus that causes “COVID”), the emergence of milder strains of the pathogen, and improved treatments. It is a welcome relief, but the decline does not help the millions of people already suffering from “long COVID.” Furthermore, experts warn that the risks are still not negligible. Without a clear explanation for the downward trend, it is unclear whether it will continue or not.
Community Immunity and Viral Strains
To begin with, greater community immunity—whether from infection, vaccination, or both—may have provided protection against persistent symptoms. There is no doubt that vaccines have offered strong defense against the virus over the past three years. Multiple studies suggest that vaccination also reduces the chances of developing “long COVID”—especially for those who stay up to date with their shots. For example, a study of cancer patients showed that the risks of developing “long COVID” were higher before vaccines were available and that participants who received a booster dose were less likely to develop “long COVID” than those who only received a partial dose. Additionally, a study published just last week found that three or more doses of a COVID vaccine reduce the risk of developing “long COVID” by 73 percent, compared to 21 percent after just one dose. While research is still inconclusive regarding whether repeat infections provide protection, a single infection combined with vaccination—also known as hybrid immunity—likely reduces future infections and illnesses.
Treatments
Treatments may also have contributed to the decline in “long COVID” cases. Antiviral medications can now help control the virus early in the infection, thereby reducing the severity of acute symptoms and their long-term effects. In March 2023, a study involving more than 280,000 veterans with “COVID” showed that those who received Paxlovid within the first five days of symptoms were about 25 percent less likely to develop “long COVID” compared to the control group. Another recent study found that overweight individuals who took another drug called metformin, which also has antiviral properties, were 41 percent less likely to develop “long COVID” compared to those who received a placebo. Cardiologist Erika Spatz from Yale University, who did not participate in the metformin study, was so impressed by the results that she now prescribes it to any COVID patients concerned about “long COVID.”
Research Challenges
However, doctors largely do not widely prescribe these medications, which likely means they are not the primary reason behind the community-wide decline of “long COVID.” It would be challenging to disentangle the other two hypotheses—population-level immunity and intrinsic changes in the virus. Ziyad Ali, a clinical epidemiologist at Washington University in St. Louis, who has led several “long COVID” studies and was the lead author of the metformin paper, would like to see an investigation covering the entire pandemic—following patients who experienced “long COVID” after infection with each variant and documenting their vaccination, infection, and antiviral use history to extract the actual cause behind this change. He points out that such a study would not be easy, especially as testing and tracking of “COVID” have slowed recently, meaning that “long COVID” patients might be undercounted. But Ali insists that such a study is feasible. It is also critical if we want to know whether “long COVID” will continue to decline.
The Future
Many argue that if community immunity is the main factor, cases of “long COVID” may continue to decline, provided that vaccination rates do not deteriorate further. Ali says, “We cannot say that vaccination reduces the risk of ‘long COVID’ by a certain percentage and then abandon it—as it seems to be the case—and expect ‘long COVID’ to continue decreasing.”
However, if the variant is more important, the future of “long COVID” will be a result of evolutionary opportunity. The virus will continue to mutate, and the next variant may be more dangerous than Omicron, potentially increasing rates of “long COVID,” not to mention deaths and hospitalizations. However, Akiko Iwasaki, an immunologist at Yale School of Medicine, says there is hope. If you are vaccinated, you may be able to withstand a more severe variant. “That’s my hope,” Iwasaki says. “Currently, there is nothing contradicting that hope. But we cannot be too comfortable. We cannot assume that future variants will be very mild.”
Ongoing Risks
Even if we are lucky, many experts argue that the diminishing risks still exist. Nicole Ford, a senior health scientist at the Centers for Disease Control and Prevention who led the agency’s investigation into “long COVID” earlier this year, points out that by the end of the study period in June 2023, approximately one in ten adults who had previously reported a COVID infection were still experiencing ongoing symptoms. Among these, one in four had difficulty performing daily activities—a concerning finding given the ongoing lack of treatment and that some patients have not fully recovered. “The lesson that can be drawn from this study is that ‘long COVID’ is common,” Ford says. “It can affect anyone completely.”
Shannon Hall is an award-winning science journalist based in the Rocky Mountains. She specializes in writing articles about astronomy, geology, and the environment.
Source: https://www.scientificamerican.com/article/long-covid-rates-appear-to-be-decreasing/
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