Vaccination prior to COVID-19 infection is associated with lower risk for long COVID and reduced symptom severity by 90 days post infection, according to results of a study published in Open Forum Infectious Diseases.
Researchers conducted a prospective, community-based cohort study from October 2020 to December 2022 to assess the protective effect of COVID-19 vaccination against long COVID. The researchers defined long COVID as the presence of ongoing symptoms by 90 days postinfection. Data were sourced from patient surveys and blood samples collected bimonthly, and diagnosis of SARS-CoV-2 infection was determined through molecular and rapid antigen testing. Patients who tested positive completed illness surveys at 30 days post infection and every 30 days thereafter until symptom resolution.
The researchers stratified patients into groups by vaccination status and history of COVID-19 infection and then compared the severity and presence of self-reported acute and long-term symptoms via Poisson and linear regression models.
A total of 1370 patients with COVID-19 infection completed illness surveys and were included in the analysis, of whom the mean age was 44.3 (range, 20-82) years, and the majority were women (84%).
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As the virus mutates and the population immune history evolves it will be important to monitor changes in long COVID patterns.
By 90 days post infection, 8% of vaccinated and 27% of unvaccinated patients reported long COVID symptoms. Vaccinated patients were significantly less likely to have any ongoing symptoms at days 30 (relative risk [RR], 0.63; 95% CI, 0.52-0.76) and 90 (RR, 0.31; 95% CI, 0.22-0.42). In addition, vaccinated patients were significantly less likely to have 5 or more ongoing symptoms at days 30 (RR, 0.37; 95% CI, 0.24-0.58) and 90 (RR, 0.34; 95% CI, 0.15-0.79).
During acute and postacute phases of infection, vaccinated patients reported lower maximum symptom severity scores compared with unvaccinated patients.
Further analysis showed that vaccinated patients more commonly reported acute upper respiratory symptoms, including sore throat (RR, 1.72; 95% CI, 1.42-2.09), nasal congestion (RR, 1.50; 95% CI, 1.27-1.77), and cough (RR, 1.44; 95% CI, 1.22-1.71). However, the severity of these symptoms did not differ between the groups.
Difficulty breathing was less commonly reported by vaccinated patients at days 30 (RR, 0.28; 95% CI, 0.18-0.44) and 90 (RR, 0.25; 95% CI, 0.12-0.55). Other symptoms less commonly reported by vaccinated patients were muscle or body aches, fatigue, chills, sleep issues, loss of smell/taste, headache, gastrointestinal events, and cognitive dysfunction.
For patients infected with COVID-19 in the pre-Omicron period, the rate of any symptoms at 90 days following infection was lower among vaccinated vs unvaccinated patients (18% vs 28%). Vaccinated patients also had lower mean and maximum symptom severity scores at 90 days post infection during this period.
In an analysis of only vaccinated patients, those infected with COVID-19 during vs before the Omicron period reported lower rates of symptoms at 90 days postinfection (6% vs 18%). Of note, loss of smell/taste among vaccinated patients was substantially less severe and less common at 90 days for those infected during the Omicron period (RR, 0.05; 95% CI, 0.02-0.11)
The researchers observed that second episodes of COVID-19 infection among vaccinated patients were neither less severe nor less likely to result in long COVID.
Study limitations include the inability to examine rare and severe long COVID outcomes due to insufficient power, potential recall bias, and insufficient follow-up time to detect a large number of second infections among vaccinated patients.
According to the researchers, “As the virus mutates and the population immune history evolves it will be important to monitor changes in long COVID patterns.”
Disclosure: One study author reported affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
