Post-Covid-19-vaccination adverse events and healthcare utilization among individuals with or without previous SARS-CoV-2 infection

Background Post-marketing pharmacovigilance data are scant on the safety of Covid-19 vaccines among people with previous SARS-CoV-2 infection compared with ordinary vaccine recipients. We compared the post-vaccination adverse events of special interests (AESI), accident and emergency room (A&E) visit, and hospitalization between these two groups. Methods We conducted a retrospective cohort study using a territory-wide public healthcare database with population-based vaccination records in Hong Kong. Results In total, 3922 vaccine recipients with previous SARS-CoV-2 infection and 1,137,583 vaccine recipients without previous SARS-CoV-2 infection were included. No significant association was observed between previous SARS-CoV-2 infection and AESI or hospitalization. Previous SARS-CoV-2 infection was significantly associated with a lower risk of A&E visit (CoronaVac: hazard ratios [HR] = 0.56, 95% confidence intervals [CI]: 0.32-0.99; Comirnaty: HR = 0.62, 95% CI: 0.47-0.82). Conclusion No safety signal of Covid-19 vaccination was detected from the comparison between vaccine recipients with previous SARS-CoV-2 infection and those without infection.

Automated summary

This study compared post-vaccination adverse events, accident and emergency room visits, and hospitalization between vaccine recipients with previous SARS-CoV-2 infection and those without infection. The results showed no significant association between previous infection and adverse events or hospitalization. However, previous SARS-CoV-2 infection was significantly associated with a lower risk of A&E visit.