Real World Effectiveness of Inactivated SARS-CoV-2 Vaccine (CoronaVac) against the COVID-19 outbreak in a hospital in northern, Thailand
Keywords:COVID-19, Vaccine, Effectiveness, Outbreak, Hospital
Amidst the pandemic of Coronavirus Disease 2019 (COVID-19), vaccination is one of key measures for controlling epidemic. This study aimed to evaluate real world vaccine effectiveness (VE) of two doses of, an inactivated SARS-CoV-2 vaccine, CoronaVac, in preventing the COVID-19 infection and pneumonia during the outbreak. A retrospective cohort study was conducted. The cohort included hospital personnel working in the wards with COVID-19 cases or providing services to the COVID-19 cases during the outbreak. All participants were tested for the genetic materials (RNA) of SARS-CoV-2 in upper respiratory specimens using RT-PCR technique during June 18 – July 1, 2021 and had vaccination information from the national vaccination database of the Ministry of Public Health Immunization Center. Data analyses performed multiple logistic regression analysis for calculating aAdjusted Odds Ratios and 95% Confidence Intervals (95% CI). Vaccine effectiveness (VE) percentages were calculated, using the unvaccinated as a comparison group. The results showed that, among 431 cohort participants, 40(9.2%) were infected with COVID-19 and 336(78.0%) received the CoronaVac for at least 14 days before the outbreak started or getting infected. Effectiveness of the CoronaVac (receiving two doses for at least 14 days), adjusted for history of close contact with COVID-19 case and working in the ward with high attack rate was 89.9% (95%CI = 74.9-95.9). Unadjusted effectiveness in preventing pneumonia was 83.9% (95% CI = 16.2-96.9). The findings from this study indicated that the effectiveness of CoronaVac which was widely used in Thailand in the first half of 2021, in preventing COVID-19 infection (Alpha variant B.1.1.7) and pneumonia during that period. The vaccine seemed to play an important role in reducing morbidity and mortality among the vaccinated population
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