COVID-19 vaccination slashed the risk of experiencing prolonged symptoms by about 27% in fully vaccinated adults who were later infected, estimates a European Centre for Disease Prevention and Control (ECDC) systematic review of 12 studies.

The researchers identified 11 studies on whether COVID-19 vaccination lowers the risk of long COVID, or post-COVID condition (PCC) and 1 study designed to determine whether vaccination reduces both the risk and duration of persistent symptoms. Published after October 2021, the studies used the World Health Organization (WHO) definition of long COVID and were conducted in Europe and similar regions.

The WHO defines long COVID as symptoms 3 months after SARS-CoV-2 infection that last for at least 2 months.

No conclusions about kids, immune-compromised adults

Six studies of adults overall found that full vaccination before infection significantly reduced the odds of developing long COVID compared with no vaccination. 

“These studies represented a range of recruitment settings (including both community and hospital settings), time period of infection (and consequently SARS-CoV-2 variant), as well as acute COVID-19 disease severity,” the study authors wrote. “In addition, two of the three studies which did not find that vaccination reduced PCC had small sample sizes, particularly where symptoms were assessed in sub-group analyses.” 

The researchers also conducted a meta-analysis using four comparable studies on whether COVID-19 vaccination lowers the risk of long COVID to quantify the pooled effect of vaccines. 

A random-effects model estimated the pooled adjusted odds ratio at 0.73, suggesting that full COVID-19 vaccination before infection could reduce the risk of long COVID by 27% relative to no vaccination in adults. But there weren’t enough well-designed studies to determine whether vaccination lowers the odds of long COVID for children or immunocompromised adults.

Findings align with previous reviews

The researchers didn’t identify any longitudinal studies that examined the persistence of COVID-19 symptoms in a defined long-COVID cohort at multiple time points, but one small study of hospitalized adults indicated that vaccination may reduce the duration of major physical symptoms but not major neuropsychologic symptoms at 12 and 18 months after hospital release.