Study of COVID-19 vaccine effectiveness

Abstract

Background: Since the coronavirus infection was declared a public health emergency of international concern in 2020, more than 772 million people have been infected and more than 6.9 million deaths have been recorded. The first COVID-19 case was reported on November 10, 2020, and by 2023 a total of 869,385 cases and 2,128 deaths have been reported. As of March 30, 2023, more than 380 vaccines were developed worldwide, and the World Health Organization has listed 15 vaccines from 11 manufacturers for emergency use and recommended for member states. The primary goal of the coronavirus infection vaccination program is to prevent severity and mortality in the target population. Thus, vaccination outcomes are evaluated with the severity and mortality risk reduction. Despite the high uptake of 4 types of vaccine, immunization effectiveness and outcomes are needed to be studied. Aim: To evaluate COVID-19 vaccination outcomes in Mongolia. Materials and Methods: A follow-up study was conducted from February 23, 2021, to December 31, 2022, within 80 (12th, 24th, and 48th week) weeks of follow-up database. The SPSS 26 software was used to analyze morbidity and mortality 1.5 years data starting from the first dose vaccination obtained from the National Health Development Center, immunization and booster dose information obtained from the Immunization Department of the National Center for Communicable Diseases (NCCD), and polymerase chain reaction (PCR) data was extracted from the Field Epidemiology Training Programme of the NCCD. Five provinces and Ulaanbaatar city’s target population (adults) were included in the study. Results: From the total of 1833 COVID-19 negative study participants, 1709 met the inclusion criteria and 839 (49.1%) confirmed the COVID-19 infection after their first vaccine dose and 107 (12.7%) (6.3% of the total participants) confirmed with the COVID-19 infection after the second dose of the vaccine using the PCR testing, and 281 (16.4%) confirmed cases were hospitalized and 2 (0.71%) (0.12% of the total participants) cases deceased. After 12 weeks of the 2nd dose vaccination, frontline workers were at higher risk than the general population, Bayankhongor province frontline workers than other provinces workers, pregnant women than other target populations, and women than men. Conclusion: Working on the frontline of the pandemic, especially in the red zone, was a risk factor for re-infection. The relative risk of re-infection for women under 39 years of age was 1.1 times higher than the general population.