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.

We studied the introduction rate after a negative challenge to mixed tree nut biscuit. This is a retrospective review of patients who underwent and passed mixed tree nut biscuit challenges performed at Princess Margaret Hospital (PMH) between 2016 and 2018. Follow-up phone calls were made to families to ascertain if the tree nuts included in the tree nut biscuit were still included in the child’s diet 1 to 3 years following negative oral food challenge (OFC). A total of 162 children underwent mixed tree nut biscuit challenge between 2016 and 2018 at Princess Margaret Hospital, Perth, Western Australia. A total of 141 (87%) passed mixed tree nut biscuit challenge. Of the 133 children that were contacted (8 children could not be contacted), 104 children still included some or all of the challenge nuts in the child’s diet; with 24 children completely eliminating the challenge nuts (18%), 5 children eliminated some of the challenge nuts (3.5%). We found a high introduction rate (82%); however, some families may require more support to maintain the tree nuts in the child’s diet following a negative OFC.

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