Efficacy of COVID-19 Vaccination on the Symptoms of Patients with Long COVID: a Target Trial Emulation Using Data from the ComPaRe E-Cohort in France

We used data from 910 adult patients included the ComPaRe long COVID cohort to emulate a target trial evaluating the effect of vaccination on the symptoms of patients who already had long COVID. We used propensity score matching to compare the outcomes, at 120 days, of patients who received a first COVID-19 vaccine injection (n=455) and those who did not (n=455). Vaccination reduced the number of long COVID symptoms (mean difference: -1.8, 95% CI -3.0 to -0.5), the proportion of patients with an unacceptable symptom state (risk difference -7.5%, 95% CI -14.4 to -0.5), and doubled the remission rate (16.6% vs 7.5%, HR: 1.97, 95% CI 1.23 to 3.15). In the vaccination group, two (0.4%) patients reported serious adverse events leading to hospitalisation. Vaccination lowered the severity and life impact of long COVID, at 120 days, among patients with persistent symptoms.