Last updated on August 27th, 2024 at 08:10 pm
A summer wave of Covid-19 infections is sweeping the country. A new study, published at just the right moment, examines the risk of long Covid and how those odds have shifted over time.
The study showed that as auspicious as it seems, the chances of getting long Covid have diminished since the beginning of the pandemic but are still considerable, especially for people who remain unvaccinated.
An analysis by the federal Agency for Healthcare Research and Quality estimated that about 7% of American adults-or approximately 18 million people-have experienced long Covid. Long Covid has cost the nation $3.7 trillion, approximately 17% of the pre-Covid gross domestic product, according to an estimate made last year by Harvard economist David Cutler.
This new study, published in the New England Journal of Medicine, confirms the grim fact that the human and financial toll of long Covid is set to grow. Advanced machine learning was used by researchers who analyzed millions of medical records from the Department of Veterans Affairs.
The Washington University at St. Louis and the VA Health System reviewed patients who developed Covid-19 during three distinct pandemic periods: before vaccines were available, during the surge of the Delta variant, and after Omicron variants became predominant. They assessed whether the risk of long Covid symptoms had changed-and accounted for vaccination status. They were considered vaccinated if they had received at least the initial series of vaccines and unvaccinated if not.
The study included more than 441,000 people who caught Covid-19 between March 2020 and January 2022 and who survived for at least 30 days post-infection. Their records were compared to those of more than 4.7 million people who did not catch Covid but who visited the VA for other reasons during the same period.
Results have shown that in the first year of the pandemic, when the original strain of the virus was in circulation with very little immunity among the population, 1 in every 10 with Covid-19 developed symptoms of long Covid. If these symptoms were new and started between 30 days and a year after infection, they would be considered, in their types, to be part of 10 disease areas.
Vaccines halved the risk of long Covid during the summer 2021 wave brought about by the Delta variant, but the risk was still high among unvaccinated persons, with almost 10 percent experiencing continued symptoms.
During the Omicron wave, which started right after Thanksgiving 2021, 3.5% of vaccinated and 7.7% of unvaccinated people developed long Covid.
Several notable limitations are identified with this study. Most treated at the VA are White men; thus, the population under study is less representative of the population in general, and the findings cannot be generalized to the whole population. For example, a recent study found that close to 1 in 10 who develop Covid-19 for the first time during pregnancy may go on to develop long Covid, a higher incidence than the general population.
The new study doesn’t differentiate between those who got just the primary series of Covid-19 vaccines and those who got boosters. It doesn’t account for immunity from past infection or reinfection, though the senior study author Dr. Ziyad Al-Aly, chief of research and development at the Veterans Affairs St. Louis Health Care System, plans to study in follow-up research.
Dr. Al-Aly said he believed that vaccines accounted for nearly three-quarters of the reduced risk of long Covid since the pandemic’s early days. He added that though the causes of long Covid were not well understood, there was evidence to suggest that people with the condition continued to harbor active virus in their body long after the initial infection. “Vaccines help the immune system suppress the viral load and clear the virus faster,” he said.
Dr. Hector Bonilla, co-director of Stanford’s Post-Acute Covid-19 Syndrome Clinic, said vaccination, nonetheless, cuts long Covid risk. He watched as new patients with lingering symptoms fell off a cliff when vaccines first became available. These days, though, his clinic has a steady stream of new patients, some of whom develop long Covid after multiple infections.
Dr. Bonilla said vaccination remains an important factor to prevent long Covid symptoms. “Vaccination is still a very important piece to prevent long Covid symptoms,” he said.
The study estimated that approximately 3 in 100 vaccinated people who catch Covid-19 now will end up with long Covid, which is an improvement but still a significant number out in the world living with disability and in ill health.
Experts not involved in the study agree that 3.5% is still a high risk of long Covid. “Large numbers of new infections and reinfections are still translating into a huge number of persons with long Covid,” said Dr. Daniel Griffin, infectious disease specialist at Columbia University who treats long Covid patients.
