Medical complaints after 3 vs 2 doses SARS-CoV-2 mRNA vaccination

Aims To examine whether individuals vaccinated with three doses of mRNA SARS-CoV-2 vaccines have an altered incidence of medical complaints compared to individuals not vaccinated with three doses. Methods Using longitudinal exact 1:1 matching on days since 2nd dose, calendar month and a set of covariates, we obtained a matched sample with 138 581 individuals aged 18-70 years that had the 3 rd dose at 20-30 weeks after the 2 nd dose and an equally large control group that did not. Main outcomes were medical records of common complaints seen in primary care for up to 90 days after the treatment. Results Depending on type of complaint, the estimated 90-day cumulative incidence varied between 70 and 5000 per 100 000 individuals. Among individuals aged 18-44 years, the number of medical complaints was lower for individuals with three doses: Fatigue: 662, 95% confidence interval=473-850, shortness of breath: 160 (90-230) and brain fog: 65 (22-108) fewer per 100 000 vaccinated. No decrease in incidence was observed for musculoskeletal pain, cough or heart palpitations. When individuals where censored from the analysis from the date of positive SARS-CoV-2 test, these absolute differences were smaller. Similar analyses gave higher estimates among individuals aged 45-70 years, yet more ambiguous results when censored at positive test. Conclusion Individuals vaccinated with dose 3 had reduced incidence of complaints compared to matched controls with only 2 doses. Analyses with vs without censoring at positive test implied that this reduction might be explained by a reduced COVID-19 incidence among the 3-dose-vaccinated.