Introduction
The epidemic caused by the
severe acute respiratory syndrome
coronavirus-2 (SARS-CoV-2) in Wuhan, China in December 2019 was
identified in February 2020 by World Health Organization (WHO) as
corona virus disease 2019
(COVID-19).1,2 SARS-CoV-2 infection may appear
asymptomatic or may present as mild upper respiratory tract disease,
however viral pneumonia may also lead to respiratory
failure.3 While the treatment research against
coronavirus pandemic continues all over the world, the group of patients
with high probability of severe disease is tried to be determined.
COVID-19 mortality and morbidity rates differ disproportionately between
countries to the level of measures and restrictions taken by them.
It is possible that the
sociocultural or lifestyle differences of citizens and the differences
in the health policies of countries make surprising differences in
COVID-19 epidemiology in different countries. Accordingly, factors
underlying the severe epidemic in some countries are tried to be
clarified. It has recently been suggested that countries’ Bacillus
Calmette-Guérin (BCG) vaccination policies can affect the epidemiology
of COVID-19.4 This hypothesis is mainly based on the
fact that countries such as Italy, who do not have a BCG-vaccination
policy, are severely affected by the COVID-19 outbreak despite
implementing high-level of social isolation measures, whereas countries
with immunization policy, such as Japan, were slightly affected by the
outbreak, even though they did not take high level of
measures.4
In the present study, the severity of COVID-19 pneumonia in BCG
vaccinated and unvaccinated people is compared and factors associated
with the severity of the disease is investigated in a country that has
been running national BCG vaccination program for nearly 70 years.