COVID-19 Vaccination Uptake and Effectiveness for Hospitalized Cases Among Healthcare Workers in Tertiary Hospital

Background/Objectives: Healthcare workers (HCWs) faced elevated risks during the coronavirus disease 2019 (COVID-19) pandemic. Vaccination among HCWs was a key strategy to mitigate severe outcomes and maintain healthcare system functionality during the crisis. The aim of this study was to assess the distribution, severity, and clinical factors associated with COVID-19 among HCWs in a tertiary hospital across eight pandemic waves and evaluate the effectiveness of vaccination in reducing severe outcomes. Methods: A cross-sectional study analyzed data from HCWs at a high-specialty hospital in Mexico City from March 2020 to February 2024. Sociodemographic, clinical, and vaccination data were collected and analyzed via bivariate and multivariable logistic regression to identify the factors associated with infection and severity. Results: A total of 7049 cases were analyzed, and 2838 (40.26%) were confirmed COVID-19 cases. Severe outcomes, including hospitalizations and deaths, were most common during the early waves, with 83.3% of severe cases occurring among unvaccinated individuals. Vaccination significantly reduced infection risk, with individuals receiving two or more doses showing a lower likelihood of infection (OR 0.67; 95% CI 0.51-0.89; p = 0.005). Older age; comorbidities such as hypertension and obesity; and symptoms such as fever were associated with increased severity. Compared with earlier coverage, enhanced vaccination coverage significantly lowered the hospitalization risk during the later waves (OR 11.11; 95% CI 1.2-110.2; p = 0.040). Conclusions: Vaccination effectively reduced severe COVID-19 outcomes among HCWs, demonstrating its critical role in mitigating the disease burden despite the high risk of exposure. Strategies such as targeted vaccination campaigns and continuous surveillance are essential to protect HCWs and ensure healthcare system resilience.