Severity of COVID-19 in bacillus Calmette-Guérin vaccinated population

Considering the cross-protection reported for bacillus Calmette-Guérin (BCG) vaccination on viral respiratory infections, it has been proposed that it could reduce the severity of coronavirus disease 2019 (COVID-19). The objective of the current study is to investigate the association between the severity of COVID-19 with prior BCG vaccination in adult patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Adult patients (18 years or above) with positive SARS-CoV-2 polymerase chain reaction admitted in July 2020 were included in this cross-sectional study. Patients were classified into non-severe, severe, and critical diseases. History of prior BCG vaccination and the presence of a BCG vaccination scar were recorded.

Out of 103 patients, 64 patients with prior history of BCG vaccinations were compared with 39 patients without BCG vaccination in childhood. The median age was 55 years and 64 years in BCG vaccinated & non-BCG vaccinated patients (p-value=0.002). There was male predominance in both groups and frequent comorbid illnesses were hypertension and diabetes mellitus. Severe COVID-19 was found in 91 patients (88.3%) followed by non-severe disease and critical diseases i.e., 7 (6.8%) and 5 (4.9%) patients, respectively. No association of prior BCG vaccination with disease severity of COVID-19 was found in this study and mortality was 8.7%. Out of nine patients who expired only 2 (22.2%) had a prior history of BCG vaccination (p-value=0.01). Secondary infections were present in 26 patients and the majority had pneumonia.

The BCG vaccine has no impact on the severity of COVID-19 but could have a protective role with a low mortality rate in already infected patients.