Vaccination Status and Outcome of Hospitalized Patients with Coronavirus Disease 2019 Before and After the Spread of Omicron Variant: An Observational Study from İzmir, Turkey.

Objective: Despite the efforts in vaccination against coronavirus disease 2019 (COVID-19), breakthrough infections occur and the need for hospitalization continues. We aimed to determine the relationship between severe acute respiratory syndrome coronavirus 2 vaccination and the severity of COVID-19 and mortality among hospitalized patients with COVID-19.

Material and methods: This cross-sectional study was conducted between September 2021 and February 2022 in a university hos- pital in Turkey. Hospitalized patients with COVID-19 (both in clinics and in intensive care units), ≥18 years old, and who had no previous COVID-19 were included in the study. The demographic characteristics, clinical data, vaccination status, and outcome of the patients were analyzed retrospectively and the relationship between vaccination status and mortality was determined statistically.

Results: Of the 674 patients, 180 (26.7%) had no vaccination, 282 (41.8%) had incomplete vaccination, and 212 (31.5%) were fully vaccinated according to the updated vaccination recommendations. While 44.0% of the patients were fully vaccinated before the occur- rence of omicron variant, 15.9% of the patients were fully vaccinated during the wave of the omicron variant. The patients with no vaccination were younger and had fewer comorbidities. The overall mortality was 31.8%. Under 50 years old, all the patients with fully vaccination survived and the patients with no vaccination or incomplete vaccination had higher (10.1%) mortality. During the omicron period, mortality was lower in fully vaccinated pateints.

Conclusion: Immunization with and booster doses of BNT162b2 should be encouraged to protect both healthy and vulnerable populations.