The Relationship between COVID-19 Severity and Bacillus Calmette-Guérin (BCG)/ Mycobacterium tuberculosis exposure history in healthcare workers: a multi-center study

Abstract

The COVID-19 pandemic has brought countries’ health services into sharp focus. It was drawn to our group’s attention that healthcare workers (HCWs) had a lower mortality rate against higher COVID-19 incidence compared to the general population in Turkey. Since risk of exposure to tuberculosis bacillus among healthcare workers are higher than the population, we aimed to investigate if there is a relationship between BCG and Mycobacterium tuberculosis exposure history with COVID-19 severity in infected HCWs. This study was conducted with 465 infected HCWs from thirty-three hospitals to assess the relationship between COVID-19 severity (according to their hospitalization status and the presence of radiological pneumonia) and BCG and Mycobacterium tuberculosis exposure history. HCWs who required hospital admission had significantly higher rates of chronic diseases, radiological pneumonia, and longer working hours in the clinics. Higher rates of history of contact and care to tuberculosis patients, history of tuberculosis, and BCG vaccine were observed in hospitalized HCWs. HCWs who had radiological pneumonia had a significantly increased ratio of history of care to tuberculosis patients and a higher family history of tuberculosis. The findings from our study suggest that the lower mortality rate despite the more severe disease course seen in infected HCWs might be due to frequent exposure to tuberculosis bacillus and the mortality-reducing effects of the BCG vaccine.

Is the course of COVID‐19 associated with tuberculin skin test diameter? A retrospective study

“…In a study investigating the effect of TB contact and BCG vaccination on the course of COVID‐19 in healthcare workers, it was found that the rate of BCG vaccination was higher in those with a history of COVID‐19‐related hospitalization, in contrast to many studies in the literature and our results. In the same study, higher mean TST results were found in outpatients compared to inpatients, although there was no significant difference 30 . We observed that patients with positive TST results were significantly more likely to have mild COVID‐19 disease compared to those with negative TST, too.…”

“…In the same study, higher mean TST results were found in outpatients compared to inpatients, although there was no significant difference. 30 We observed that patients with positive TST results were significantly more likely to have mild COVID-19 disease compared to those with negative TST, too.…”

impact of Bacillus Calmette-Guérin (BCG) vaccination on the course of COVID-19

“…Other study basing on surveys (n = 1,233) suggested that intake of BCG in childhood may increase risk of COVID-19 infection [33]. A Turkish multi-centre study suggests that exposition to M. tuberculosis (infected patient or vaccine) results with more severe course, but lower mortality to COVID-19 in healthcare workers [34]. An Italian survey-based research showed no significant difference in COVID-19 prevalence among physicians vaccinated by BCG [35].…”

Prospects on Repurposing a Live Attenuated Vaccine for the Control of Unrelated Infections

“…These fall into two categories ( 1 ): the effect of childhood BCG vaccination on COVID-19 and ( 2 ) the effect of re-vaccination on COVID-19 in adults. BCG vaccination in childhood was associated with decreased SARS-CoV-2 prevalence or mortality among health care workers ( 44 , 45 ); however, in clinical studies, the protective effect of re-vaccination with BCG in adults was controversial. One randomized clinical trial showed that BCG vaccination in the elderly was correlated with lower incidence of SARS-CoV-2 infection ( 46 ).…”