COVID-19 Disease Incidence and Severity in Previously Infected Unvaccinated Compared with Previously Uninfected Vaccinated Persons

Using the VA COVID-19 National Database, we created matched pairs of previously uninfected vaccinated (≥2 doses of an mRNA vaccine) and previously infected unvaccinated individuals. The incidence rate (per 1000 person-days) of breakthrough infection among vaccinated individuals (0.30, 95% CI 0.29-0.32) was similar to reinfection rate among unvaccinated individuals (0.31, 95% CI 0.30-0.32; p=0.5). The incidence rate of hospitalization/death was higher after reinfection (7.31, 95% CI 6.66-8.03) compared with rate after breakthrough infection (4.69, 95% CI 4.06-5.42; P<0.0001). Conclusion: The incidence of hospitalization/death is significantly higher after reinfection among unvaccinated individuals compared with breakthrough infection after vaccination.