COVID-19 Vaccination and Lethality Reduction: A Prospective Cohort Study in Venezuela

Abstract

Background While rigorous randomized clinical trials have substantiated the efficacy of COVID-19 vaccines in reducing hospitalization and mortality rates, there is a paucity of post-authorization analyses conducted in real-world settings. In Venezuela, the primary vaccines administered are BBIBP-CorV (Sinopharm) and Gam-COVID-Vac (Sputnik-V). However, the performance and effectiveness of these vaccines within this specific population remain to be thoroughly investigated. Methods A prospective cohort study was undertaken from October 5, 2021, to March 31, 2022, across four sentinel hospitals in Venezuela. The outcomes were evaluated at two time points: day 28 and day 48, utilizing the WHO’s COVID-19 Clinical Progression Scale. For the purpose of analysis, patients were classified into two groups: vaccinated and unvaccinated. Results The study included a total of 175 patients, of which 85 (48.6%) were categorized as vaccinated, with the majority (76.5%) having received two doses. The median age of the patients was 68 years, with a slight predominance of females (53.1%), and the majority being unemployed/retired (60.6%). Hypertension (53.1%) and diabetes (18.3%) were the most prevalent comorbidities. The median Charlson index of the patients was 3 points, with no statistically significant differences observed between the groups (p = 0.2). Upon admission, dyspnea was more commonly observed in unvaccinated patients compared to vaccinated patients (76.7% vs. 62.4%, p = 0.039). Almost all laboratory parameters were comparable in both groups, with the exception of the median D-dimer level, which was significantly higher in unvaccinated patients (7.6 vs. 1.4 µg/mL, p = 0.015). A total of 50 patients (28.6%) died of the disease, with a higher proportion of deaths observed in unvaccinated patients compared to vaccinated patients (35.6% vs. 21.2%, p = 0.035). Factors such as advanced age (OR = 1.043, 95%CI = 1.015–1.071, p = 0.002) were associated with increased odds of death, while factors such as vaccination against COVID-19 (OR = 0.428, 95%CI = 0.185–0.99, p = 0.047), high oxygen saturation (OR = 0.964, 95%CI = 0.934–0.995, p = 0.024), and enoxaparin administration (OR = 0.292, 95%CI = 0.093–0.917, p = 0.035) were associated with decreased odds of death. Conclusion In the course of the third and fourth waves of the pandemic, vaccination against COVID-19 was found to be associated with a 57% reduction in lethality among patients treated in four public hospitals in Venezuela.