BCG to Protect against Covid-19 in Health Care Workers

The mark of success: The role of vaccine-induced skin scar formation for BCG and smallpox vaccine-associated clinical benefits

Skin scar formation following Bacille Calmette-Guérin (BCG) or smallpox (Vaccinia) vaccination is an established marker of successful vaccination and 'vaccine take'. Potent pathogen-specific (tuberculosis; smallpox) and pathogen-agnostic (protection from diseases unrelated to the intentionally targeted pathogen) effects of BCG and smallpox vaccines hold significant translational potential. Yet despite their use for centuries, how scar formation occurs and how local skin-based events relate to systemic effects that allow these two vaccines to deliver powerful health promoting effects has not yet been determined. We review here what is known about the events occurring in the skin and place this knowledge in the context of the overall impact of these two vaccines on human health with a particular focus on maternal-child health.

BCG vaccination is associated with longitudinal changes in systemic eicosanoid levels in elderly individuals: A secondary outcome analysis

We investigated how BCG vaccination affects the levels of certain eicosanoids, namely Leukotriene B4, 15-epimer of LXA4, prostaglandin F2, Lipoxin A4, Prostaglandin E2 and Resolvin D1 in the plasma of healthy elderly individuals (aged 60-80) before vaccination, one month post-vaccination (M1), and six months post-vaccination (M6). This study is part of the clinical trial "BCG Vaccine Study: Reducing COVID-19 Impact on the Elderly in Indian Hotspots," registered in the clinical trial registry (NCT04475302). While some primary outcomes have been previously reported, this analysis delves into the immunological outcomes. Our findings indicate that BCG vaccination leads to reduced plasma levels of 15-epi-LXA4, LXA4, PGE2, and Resolvin D1 at both M1 and M6. In contrast, there is a notable increase in circulating levels of LTB4 at these time points following BCG vaccination. This underscores the immunomodulatory effects of BCG vaccination and hints at its potential to modulate immune responses by dampening inflammatory reactions.

Late in the US pandemic, multi-dose BCG vaccines protect against COVID-19 and infectious diseases

The Bacillus Calmette-Guérin vaccine has many off-target benefits, including protection from diverse infectious diseases. As SARS-CoV-2 evolved, COVID-19 disease became more transmissible and less lethal. In this Phase III double-blinded, placebo-controlled trial conducted late in the pandemic, we tested at-risk US adults with type 1 diabetes if multi-dose BCG protected against COVID-19 and other infectious disease, co-primary outcomes. From April 2021 to November 2022, Tokyo-strain BCG vaccines provided significant protection against COVID-19 disease (p = 0.023) and strong platform protection against all infectious diseases (p < 0.0001). Over the course of the study, commercial COVID-19 vaccines were rolled out, most of which were mRNA-based. In contrast to the protection afforded by BCG, as reported by others, COVID-19 mRNA vaccine alone provided no protection from COVID-19 disease (p = 0.43). BCG vaccination efficacy was unaffected by concurrent COVID-19 vaccinations; COVID-19 vaccines neither helped nor hindered BCG protection.

Bacille Calmette-Guérin vaccination to prevent febrile and respiratory illness in adults (BRACE): secondary outcomes of a randomised controlled phase 3 trial

Background

Bacille Calmette-Guérin (BCG) vaccination has off-target (non-specific) effects that are associated with protection against unrelated infections and decreased all-cause mortality in infants. We aimed to determine whether BCG vaccination prevents febrile and respiratory infections in adults.

Methods

This randomised controlled phase 3 trial was done in 36 healthcare centres in Australia, Brazil, the Netherlands, Spain, and the United Kingdom. Healthcare workers were randomised to receive BCG-Denmark (single 0.1 ml intradermal injection) or no BCG in a 1:1 ratio using a web-based procedure, stratified by stage, site, age, and presence of co-morbidity. The difference in occurrence of febrile or respiratory illness were measured over 12 months (prespecified secondary outcome) using the intention-to-treat (ITT) population. This trial is registered with ClinicalTrials.gov, NCT04327206.

Findings

Between March 30, 2020, and April 1, 2021, 6828 healthcare workers were randomised to BCG-Denmark (n = 3417) or control (n = 3411; no intervention or placebo) groups. The 12-month adjusted estimated risk of ≥1 episode of febrile or respiratory illness was 66.8% in the BCG group (95% CI 65.3%-68.2%), compared with 63.4% in the control group (95% CI 61.8%-65.0%), a difference of +3.4 percentage points (95% CI +1.3% to +5.5%; p 0.002). The adjusted estimated risk of a severe episode (defined as being incapacitated for ≥3 consecutive days or hospitalised) was 19.4% in the BCG group (95% CI 18.0%-20.7%), compared with 18.8% in the control group (95% CI 17.4%-20.2%) a difference of +0.6 percentage points (95% CI -1.3% to +2.5%; p 0.6). Both groups had a similar number of episodes of illness, pneumonia, and hospitalisation. There were three deaths, all in the control group. There were no safety concerns following BCG vaccination.

Interpretation

In contrast to the beneficial off-target effects reported following neonatal BCG in infants, a small increased risk of symptomatic febrile or respiratory illness was observed in the 12 months following BCG vaccination in adults. There was no evidence of a difference in the risk of severe disease.

Funding

Bill & Melinda Gates Foundation, Minderoo Foundation, Sarah and Lachlan Murdoch, the Royal Children's Hospital Foundation, Health Services Union NSW, the Peter Sowerby Foundation, SA Health, the Insurance Advisernet Foundation, the NAB Foundation, the Calvert-Jones Foundation, the Modara Pines Charitable Foundation, the UHG Foundation Pty Ltd, Epworth Healthcare, the National Health and Medical Research Council, the Swiss National Science Foundation and individual donors.

The association between BCG scars and self-reported chronic diseases: A cross-sectional observational study within an RCT of Danish health care workers

INTRODUCTION

The live-attenuated vaccines Bacillus Calmette-Guérin (BCG) and Vaccinia have been associated with beneficial non-specific effects. We assessed the prevalence of BCG and Vaccinia vaccine scars in a cohort of Danish health care workers and investigated the association between the presence of vaccine scars and self-reported chronic diseases.

METHODS

Cross-sectional study utilizing baseline data collected during 2020-2021 at enrollment in a BCG trial aiming to assess the effect of BCG vaccination on absenteeism and infectious disease morbidity during the SARS-COV-2 pandemic. In Denmark, Vaccinia was discontinued in 1977, and BCG was phased out in the early 1980s. We used logistic regression analysis (adjusted for sex, birth year, and smoking status) to estimate the association between scar status and chronic diseases, providing adjusted Odds Ratios (aORs) with 95 % Confidence Intervals, for participants born before 1977, and born from 1965 to 1976.

RESULTS

The cohort consisted of 1218 participants (206 males; 1012 females) with a median age of 47 years (Q1-Q3: 36-56). Among participants born 1965-1976 (n = 403), who experienced the phase-outs, having BCG and/or Vaccinia scar(s) vs. having no vaccine scars yielded an aOR of 0.51 (0.29-0.90) of self-reported chronic disease; an effect primarily driven by BCG. In the same birth cohort, having vaccine scar(s) was most strongly associated with a lower prevalence of chronic respiratory and allergic diseases; the aORs being 0.39 (0.16-0.97) and 0.39 (0.16-0.91), respectively.

CONCLUSION

Having a BCG scar was associated with a lower prevalence of self-reported chronic disease.

Using BCG Vaccine to Enhance Nonspecific Protection of Health Care Workers During the COVID-19 Pandemic: A Randomized Controlled Trial

BACKGROUND

The BCG (Bacillus Calmette-Guérin) vaccine can induce nonspecific protection against unrelated infections. We aimed to test the effect of BCG on absenteeism and health of Danish health care workers (HCWs) during the coronavirus disease 2019 (COVID-19) pandemic.

METHODS

A single-blinded randomized controlled trial included 1221 HCWs from 9 Danish hospitals. Participants were randomized 1:1 to standard dose BCG or placebo. Primary outcome was days of unplanned absenteeism. Main secondary outcomes were incidence of COVID-19, all-cause hospitalization, and infectious disease episodes.

RESULTS

There was no significant effect of BCG on unplanned absenteeism. Mean number of days absent per 1000 workdays was 20 in the BCG group and 17 in the placebo group (risk ratio, 1.23; 95% credibility interval, 0.98-1.53). BCG had no effect on incidence of COVID-19 or all-cause hospitalization overall. In secondary analyses BCG revaccination was associated with higher COVID-19 incidence (hazard ratio [HR], 2.47; 95% confidence interval [CI], 1.07-5.71), but also reduced risk of hospitalization (HR, 0.28; 95% CI, .09-.86). The incidence of infectious disease episodes was similar between randomization groups (HR, 1.09; 95% CI, .96-1.24).

CONCLUSIONS

In this relatively healthy cohort of HCWs, there was no overall effect of BCG on any of the study outcomes.

CLINICAL TRIALS REGISTRATION

NCT0437329 and EU Clinical Trials Register (EudraCT number 2020-001888-90).