The incidence of long COVID dropped from 10.42 to 3.50 events per 100 persons from the pre-delta to omicron eras, with vaccines playing a crucial role in this reduction, according to a recent study.
The study, published in The New England Journal of Medicine, documented a decline in the incidence of postacute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (PASC), also known as long COVID, across the pre-delta, delta, and omicron eras. The analysis included data from 441,583 veterans with SARS-CoV-2 infection and 4,748,504 noninfected controls from the U.S. Department of Veterans Affairs' health records.
The cumulative incidence of PASC among unvaccinated patients was 10.42 events per 100 persons (95% confidence interval [CI], 10.22-10.64) during the pre-delta era, 9.51 events (95% CI, 9.26-9.75) during the delta era, and 7.76 events (95% CI, 7.57-7.98) during the omicron era. Among vaccinated patients, the incidence was 5.34 events per 100 persons (95% CI, 5.10-5.58) during the delta era and 3.50 events (95% CI, 3.31-3.71) during the omicron era. The study indicated that COVID-19 vaccination reduced the incidence of PASC, with a difference of 4.26 events per 100 persons (95% CI, 4.49-4.05) between vaccinated and unvaccinated individuals during the omicron era.
The incidence of PASC decreased by 2.66 events per 100 persons (95% CI, −2.93 to −2.36) from the pre-delta era to the omicron era, and by 1.75 events per 100 persons (95% CI, −2.08 to −1.42) from the delta era to the omicron era. At 1 year, the cumulative incidence of PASC was lower in vaccinated individuals compared to unvaccinated individuals, with a difference of 4.18 events per 100 persons (95% CI, −4.47 to −3.88) during the delta era and 4.26 events per 100 persons (95% CI, −4.49 to −4.05) during the omicron era.
Decomposition analyses indicated a reduction of 5.23 PASC events per 100 persons (95% CI, 4.97 to 5.47) at 1 year during the omicron era compared to the combined pre-delta and delta eras. Of this reduction, 71.89% of the decrease (95% CI, 69.50% to 74.43%) was attributed to vaccination, and 28.11% (95% CI, 25.57% to 30.50%) was related to era-specific factors, including changes in the virus and other temporal effects.
Analyses by disease category indicated a reduced risk of sequelae in most categories, though the omicron era saw an increased risk of gastrointestinal, metabolic, and musculoskeletal disorders compared to the combined pre-delta and delta eras. For vaccinated individuals, almost all disease categories had a lower cumulative incidence of PASC, with none showing a higher incidence during the omicron era compared to the delta era. However, the incidence of PASC remains notable even among vaccinated individuals in the omicron era, concluded the study's authors.
Full disclosures can be found in the published study.