COVID-19 Vaccine Effectiveness on the Severity of Disease: A Case-control Study in Southeastern Iran

Considering the importance of the effectiveness of vaccination in terms of reducing the severity of COVID-19 and mortality, knowledge of the effect of the vaccine on the severity of COVID-19 in communities is essential. Therefore, the purpose of this study was to evaluate the effect of the COVID-19 vaccine on the severity of COVID-19 in southeastern Iran (Bam region). A case-control study of a total of 2,082 adults aged >18 years was conducted to evaluate the association between hospitalization due to COVID-19 and previous vaccination with existing vaccines (including Sinopharm, AstraZeneca, and CovIran Barkat) in the country. Multinomial logistic regression was used, and relative risk (RR) and 95% confidence intervals (CIs) were calculated After controlling for potential confounders, multinomial logistic regression revealed that COVID-19 vaccination reduced the likelihood of hospitalization for males and females in temporary wards (RRmen=0.22 vs. RRwomen=0.34), general wards (RRmen=0.25 vs RRwomen=0.31), and intensive care units (RRmen=0.47 vs RRwomen=0.77) (p < 0.001). The relative risk of hospitalization in all wards decreased for men and women who received Sinopharm or AstraZeneca and for women who received the Barkat vaccine, but only a significant difference was detected in the reduction in patients who received the Sinopharm vaccine (p < 0.001). The results showed that vaccination is related to reducing the severity of the disease in the hospital. Therefore, efforts to increase the vaccinated population can reduce the severity of COVID-19 and might reduce the need for intensive care in hospitals.