Background and objectives Because of its beneficial off‐target effects against non‐mycobacterial infectious diseases, bacillus Calmette–Guérin (BCG) vaccination might be an accessible early intervention to boost protection against novel pathogens. Multiple epidemiological studies and randomised controlled trials (RCTs) are investigating the protective effect of BCG against coronavirus disease 2019 (COVID‐19). Using samples from participants in a placebo‐controlled RCT aiming to determine whether BCG vaccination reduces the incidence and severity of COVID‐19, we investigated the immunomodulatory effects of BCG on in vitro immune responses to SARS‐CoV‐2. Methods This study used peripheral blood taken from participants in the multicentre RCT and BCG vaccination to reduce the impact of COVID‐19 on healthcare workers (BRACE trial). The whole blood taken from BRACE trial participants was stimulated with γ‐irradiated SARS‐CoV‐2‐infected or mock‐infected Vero cell supernatant. Cytokine responses were measured by multiplex cytokine analysis, and single‐cell immunophenotyping was made by flow cytometry. Results BCG vaccination, but not placebo vaccination, reduced SARS‐CoV‐2‐induced secretion of cytokines known to be associated with severe COVID‐19, including IL‐6, TNF‐α and IL‐10. In addition, BCG vaccination promoted an effector memory phenotype in both CD4+ and CD8+ T cells, and an activation of eosinophils in response to SARS‐CoV‐2. Conclusions The immunomodulatory signature of BCG’s off‐target effects on SARS‐CoV‐2 is consistent with a protective immune response against severe COVID‐19.

Introduction The aim of this study was to evaluate the suitability of using cone‐beam computed tomography (CBCT) obtained with a mobile C‐arm X‐ray fluoroscopy unit as a single modality for planning of high‐dose‐rate (HDR) prostate brachytherapy treatments. Methods The feasibility of using CBCT images obtained using a Siemens Arcadis Orbic 3D mobile C‐arm was evaluated. A retrospective clinical study was undertaken of six participants undergoing HDR prostate brachytherapy. Plans generated using images from a Toshiba Aquilion One LB CT were compared with those generated using CBCT images. After rigid spatial registration, the plans were compared based on various parameters such as dose‐volume histograms, overlap quantities and metrics, and dose constraints. Results Provided they were within the limited field of view, the brachytherapy catheters and fiducial markers were clearly visible in the CBCT images and thus, localisable and identifiable in the treatment planning process. The Siemens CBCT underestimated CT numbers leading to poorer tissue contrast which exacerbated the difficulties in delineation of the target tumour and the surrounding organs at risk. Between CT‐ and CBCT‐based plans, the mean difference of CTV‐D90 was 1.58 Gy, CTV‐V100 was 12.13%, rectum‐V80 was 0.06% and urethra‐V120 was −0.70%. Conclusion It was not feasible to solely utilise the Siemens Arcadis Orbic 3D for HDR prostate brachytherapy treatment planning due to suboptimal organ delineation. However, the methods in this study could be used to evaluate other mobile CBCT imaging devices for feasibility in HDR brachytherapy treatment planning since the results indicated that it may not be necessary to have standard quality CT images for treatment planning.

Globally, health-care workers (HCWs) have experienced a disproportionate burden of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection that causes coronavirus disease 2019 (COVID-19), reflecting their increased risk of exposure. 1 In Victoria, 20 502 people (as of 29 April 2021) have been infected with SARS-CoV-2, of which 17% of cases are HCWs. 2,3