Covid-19 severity and neonatal bcg vaccination among young population in Taiwan

Background: Data have not been reported to explore the relation between COVID-19 severity and BCG vaccination status at the individual patient level. Methods: Taiwan has a na-tionwide neonatal BCG vaccination program that was launched in 1965. The Taiwan Centers for Disease Control established a web-based National Immunization Information System (NISS) in 2003 and included all citizens’ BCG vaccination records in NISS for those born after 1985. We identified COVID-19 Taiwanese patients born after 1985 between 21 January and 19 March 2021. Study participants were further classified into ages 4–24 years (birth year 1996–2016) and 25–33 years (birth year 1986–1995). We described their clinical syndrome defined by the World Health Organization and examined the relation between the COVID-19 severity and BCG vaccination status. Results: In the 4–24 age group, among 138 BCG vaccinated individuals, 80.4% were asymptomatic or had mild disease, while 17.4% had moderate disease, 1.5% had severe disease, and 0.7% had acute respiratory distress syndrome but none of them died. In contrast, all 6 BCG unvaccinated individuals in this age group experienced mild illness. In the 25–33 age group, moderate disease occurred in 14.2% and severe disease occurred in 0.9% of the 106 patients without neonatal BCG vaccination records, as compared to 19.2% had moderate disease and none had severe or critical disease of the 78 patients with neonatal BCG vaccination records. Conclusions: Our finding indicated that BCG immunization might not relate to COVID-19 severity in the young population.