Supalert Nedsuwan
Chiangrai Prachanukroh Hospital, ThailandTitle: Real World Effectiveness of Inactivated SARS-CoV-2 Vaccine (CoronaVac) against the COVID-19 outbreak in a hospital in northern, Thailand
Abstract
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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