Clinical outcomes in vaccinated and unvaccinated patients with COVID-19: a population-based analysis

OBJECTIVE: Real-life data for vaccination against COVID-19 are sorely needed. This was a population-based analysis aiming at investigating the hospitalization risk for COVID-19 of 98,982 subjects and compare features of vaccinated and unvaccinated patients. PATIENTS AND METHODS: Hospitalized patients with COVID-19 between 01/07/2021 and 11/02/2022 were included in the study. RESULTS: 582 patients were included in the analysis [males: 58.6% (n=341), vaccinated patients: 28.5% (n=166), unvaccinated patients: 71.5% (n=416)]. Median age of vaccinated patients was significantly higher compared to median age of unvaccinated [74.0 (95% CI: 72.0-77.0) vs. 59.0 (95% CI: 57.0-62.0), p=0.0001]. Mean latency time (+/- SD) from the second dose to hospitalization was 5.7 +/- 2.6 months. Between 01/07/2021 and 01/12/2021, unvaccinated subjects had higher risk for hospitalization compared to vaccinated [HR: 2.82, 95% CI: 2.30-3.45, p < 0.0001]. Between 02/12/2021 and 11/02/2022, unvaccinated subjects presented with higher risk for hospitalization than subjects that had received booster dose [HR: 2.07, 95% CI: 1.44-2.98, p=0.005], but not than subjects that got two doses. Median value of hospitalization days was higher in unvaccinated patients compared to vaccinated [7.0 (95% CI: 7.0-8.0) vs. 6.0 (95% CI: 5.0-7.0), p=0.02]. Finally, age-adjusted analysis showed that hospitalized unvaccinated patients presented with significantly higher mortality risk compared to hospitalized vaccinated patients [HR: 2.59, 95% CI: 1.69-3.98, p < 0.0001]. CONCLUSIONS: Vaccination against COVID-19 remains the best way to contain the pandemic. There is an amenable need for booster dose during the omicron era.