Effectiveness of COVID-19 Vaccines in Mahabad, Iran: A Cohort Study.

The COVID-19 pandemic has demonstrated the seriousness of infectious diseases , underscoring the critical role of vaccination in preventing such outbreaks. The aim of study was to examine the effectiveness of the vaccines against COVID-19 in city of Mahabad in the northwestern region of Iran. This retrospective cohort study compared 1077 vaccinated employees of the Mahabad city health department ( the exposed group) with 1338 unvaccinated employees from other departments (the unexposed group). Demographic details, vaccination dates, types, and outcomes were extracted from the local health system. Data on cases came from the disease unit, and hospitalization came from the Medical Care Monitoring Center (MCMC). Attributable fractions for the exposed group and relative risks with 95% confidence intervals were calculated for each vaccine dose, stratified by sex, age group, and exposure level. Data analysis was conducted using STATA16, with a p-value < 0.05 was considered statistically significant. The overall efficacy of COVID-19 vaccines in preventing the disease is 51%, with 26% effectiveness in preventing hospitalization. When stratified by vaccine type, AstraZeneca exhibits an 81% efficacy (95% CI: 0.61-0.91) in preventing infection. This is followed by Sputnik at 41% efficacy (95% CI: 0.086-0.62) and Sinopharm-Baharat at 10% efficacy (95% CI: 0.50-0.46). Similarly, AstraZeneca demonstrates a 79% efficacy (95% CI: 0.083-0.95), Sputnik demonstrates 29% efficacy (95% CI: 0.77-0.71), and Sinopharm-Bharat at 44% efficacy (95% CI: 0.63-0.81) in preventing hopitalization. Notably the efficacy of preventing both disease and hospitalization is higher in men than women. The AstraZeneca vaccine is the most effective at preventing both disease and hospitalization, followed by Sputnik. Analyzing vaccine effectiveness across age groups reveals the lowest efficacy in individuals below 30 years old, and the highest efficacy individuals above 51 years. Despite challenges of selecting and administering vaccines in a timely manner in Iran, our findings demonstrate that three doses of COVID-19 vaccines are over 75% effective at preventing hospitalization and death, underscoring the vital role of vaccination as a primary preventive measure against infectious disease outbreaks. These results highlight the importance of proactive preparation and investment in robust vaccination programs for effective epidemic control.