Factors determining COVID-19 pneumonia severity in a country with routine BCG vaccination

The impact of countries' bacillus Calmette-Guérin (BCG) vaccination policies on the course of coronavirus disease (COVID-19) outbreak is a curiosity. In this study, the relationship between BCG vaccination status and severity of COVID-19 pneumonia and the factors affecting disease severity were investigated.

A retrospective cross-sectional study was conducted between March and June 2020 in patients diagnosed with COVID-19 pneumonia, confirmed by severe acute respiratory syndrome coronavirus-2 polymerase chain reaction positivity in a nasopharyngeal sample and pulmonary infiltrates in computed chest tomography, in a state hospital in Istanbul, Turkey. Socio-demographic features, body mass index, smoking status, concomitant diseases, income rates and BCG vaccination status of subjects were analyzed.

The study population comprised 123 adults with COVID-19 pneumonia [mean age = 49·7 years, standard deviation = 13·3 years; 82 (66·7%) male]. While the rate of cases vaccinated with BCG is lower (68·5 versus 88·2%, P = 0·026), mean age (54·0 ± 11·5 years versus 38·3 ± 10·7 years; P < 0·001), diabetes (32·6 versus 5·9%, P = 0·002) and low income (84·3 versus 52·9%, P < 0·001) are higher in patients with severe disease compared to those with mild disease. According to multivariate analysis increasing age [odds ratio (OR) = 1·119; 95% confidence interval (CI) = 1·062-1·178, P < 0·001] and low income (OR = 3·209; 95% CI = 1·008-10·222, P = 0·049) are associated with severe disease in COVID-19 pneumonia.

This study reveals that BCG vaccination is not associated with disease severity in COVID-19 pneumonia. Age and low income are the main determinants of severe COVID-19 pneumonia.