COVID-19 patients vaccinated against the novel coronavirus were less likely to have symptoms of post-COVID condition (PCC), or long COVID, according to a new study in Nature Communications.
The study was based on outcomes seen among patients in eight large healthcare systems in the United States who had positive SARS-CoV-2 tests between March 2021 and February 2022.
The authors of the study defined PCC as a new diagnosis in one of 13 PCC categories 30 days to 6 months following a positive SARS-CoV-2 test.
The authors matched 161,531 vaccinated COVID-19 patients to unvaccinated patients using electronic health records. Of the vaccinated patients, 96.7% had two doses of COVID-19 vaccine, and among both vaccinated and unvaccinated patients, less than 1% of included COVID-19 cases had evidence of SARS-CoV-2 re-infection.
Most patients contracted virus during Omicron
"Most patients with SARS-CoV-2 were identified in December 2021 and January 2022, approximately reflecting the time period during which Omicron was the dominant circulating variant and COVID-19 vaccination coverage was high in the US," the authors said.
Most patients with SARS-CoV-2 were identified in December 2021 and January 2022, approximately reflecting the time period during which Omicron was the dominant circulating variant.
The average age of COVID-19 patients was 37.1 years, and 37.1% were White, while 36.2% were Hispanic.
During an average 151-day follow-up period, the authors found the risk of PCC was significantly lower for vaccinated than for unvaccinated patients for 9 of the 13 outcomes studied.
Vaccination was associated with a greater than 10% lower risk of sensory (relative risk [RR], 0.90), circulatory (RR, 0.88), blood and hematologic (RR, 0.79), skin and subcutaneous (RR, 0.69), and non-specific COVID-related disorders (RR, 0.53).
Vaccinated patients, however, were at a slightly increased risk of mental illness compared with unvaccinated patients over the study period (RR, 1.06).
US has most clinical long-COVID studies
In other long-COVID research news, a study in the International Journal of Infectious Diseases describes new estimates of long-COVID incidence and clinical study trends in a number of regions.
Overall, the incidence of long COVID was 31% in North America, 44% in Europe, and 51% in Asia.
The authors said the proportion of long-COVID studies investigating potential treatments increased from 45.7% (95% confidence interval [CI], 31.3% to 60.1%) in 2020 to 64.9% (95% CI, 57.3% to 72.5%) in 2023, with an average annual percentage change of 15.7%.
A total of 312 studies were found to be testing potential therapies for long COVID. Of these, the United States conducted 18.6% of clinical studies on long COVID between 2020 and 2023, followed by India (17.6%), and Spain (6.4%).
"In contrast, more long COVID studies are needed for European long COVID population,” the authors said.
