Long COVID Risk Declined Over the Pandemic: Daily Dose

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Patient Care brings primary care clinicians a lot of medical news every day—it’s easy to miss an important study. The Daily Dose provides a concise summary of one of the website's leading stories you may not have seen.

On July 18, 2024, we reported on findings from a study published in the New England Journal of Medicine that examined whether the risk and burden of long COVID changed over the course of the pandemic.

The study

Researchers compared health records from the US Department of Veterans Affairs for 441 583 veterans with SARS-CoV-2 infection between March 2020 and January 31, 2022, and 4 748 504 uninfected controls. They looked specifically at the rates of long COVID 1 year after virus infection during 3 phases of the pandemic: pre-delta (before vaccines were available), the domination of the delta variant, and the period of the omicron variant (beginning December 2021).

The findings

The cumulative incidence of long COVID at 1-year post-infection decreased from a high of 10.42 cases per 100 persons among unvaccinated participants during the pre-delta era to a low of 3.50 cases per 100 persons among vaccinated individuals during the later omicron era.

Looking more closely at vaccinated vs unvaccinated individuals by variant era, 10.42 out of 100 developed long COVID 1 year after infection in the early pandemic months, before vaccines were available. With the arrival and tenure of the delta variant (June 19, 2020, through December 18, 2021) slightly fewer unvaccinated people (9.51 out of 100) received a long COVID diagnosis but just slightly more than half that many who were vaccinated (5.34 out of 100), were diagnosed a year after infection resolved. In the omicron era (began December 19, 2021) long COVID was diagnosed in 7.76 out of 100 unvaccinated people but only in 3.5 out of 100 vaccinated individuals.

The cumulative incidence of long COVID at 1 year was lower per 100 people among vaccinated compared with unvaccinated persons (average difference across delta and omicron eras, -4.22 events).

When researchers conducted decompensation analyses of the change in cumulative incidence of long COVID over the study period, they found there were 5.23 fewer long COVID diagnoses per 100 persons 1-year post-infection during the omicron era than during the pre-delta and delta eras combined. They calculated that 28.11% of the decrease could be attributed variant characteristics during each era while the remainder of the difference, 71.89%, was related to the effect of vaccines.

Investigators also emphasized that even with the overall decline, the lowest rate of long COVID among vaccinated individuals— 3.5% — remains a substantial risk.

Authors' comment

"The cumulative incidence of PASC [postacute sequelae of severe acute respiratory syndrome] during the first year after SARS-CoV-2 infection decreased over the course of the pandemic, but the risk of PASC remained substantial even among vaccinated persons who had SARS-CoV-2 infection in the omicron era."

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