Randomized Trial of BCG Vaccine to Protect against Covid-19 in Health Care Workers.

BACKGROUND: The bacille Calmette-Guérin (BCG) vaccine has immunomodulatory "off-target" effects that have been hypothesized to protect against coronavirus disease 2019 (Covid-19). METHODS: In this international, double-blind, placebo-controlled trial, we randomly assigned health care workers to receive the BCG-Denmark vaccine or saline placebo and followed them for 12 months. Symptomatic Covid-19 and severe Covid-19, the primary outcomes, were assessed at 6 months; the primary analyses involved the modified intention-to-treat population, which was restricted to participants with a negative test for severe acute respiratory syndrome coronavirus 2 at baseline. RESULTS: A total of 3988 participants underwent randomization; recruitment ceased before the planned sample size was reached owing to the availability of Covid-19 vaccines. The modified intention-to-treat population included 84.9% of the participants who underwent randomization: 1703 in the BCG group and 1683 in the placebo group. The estimated risk of symptomatic Covid-19 by 6 months was 14.7% in the BCG group and 12.3% in the placebo group (risk difference, 2.4 percentage points; 95% confidence interval [CI], -0.7 to 5.5; P = 0.13). The risk of severe Covid-19 by 6 months was 7.6% in the BCG group and 6.5% in the placebo group (risk difference, 1.1 percentage points; 95% CI, -1.2 to 3.5; P = 0.34); the majority of participants who met the trial definition of severe Covid-19 were not hospitalized but were unable to work for at least 3 consecutive days. In supplementary and sensitivity analyses that used less conservative censoring rules, the risk differences were similar but the confidence intervals were narrower. There were five hospitalizations due to Covid-19 in each group (including one death in the placebo group). The hazard ratio for any Covid-19 episode in the BCG group as compared with the placebo group was 1.23 (95% CI, 0.96 to 1.59). No safety concerns were identified. CONCLUSIONS: Vaccination with BCG-Denmark did not result in a lower risk of Covid-19 among health care workers than placebo. (Funded by the Bill and Melinda Gates Foundation and others; BRACE ClinicalTrials.gov number, NCT04327206.).

NF-κB control of T cell development.

The NF-κB signal transduction pathway is best known as a major regulator of innate and adaptive immune responses, yet there is a growing appreciation of its importance in immune cell development, particularly of T lineage cells. In this Review, we discuss how the temporal regulation of NF-κB controls the stepwise differentiation and antigen-dependent selection of conventional and specialized subsets of T cells in response to T cell receptor and costimulatory, cytokine and growth factor signals.

Inappropriate prescribing contributes to high antibiotic exposure in young children in Australia.

BACKGROUND: Antibiotic exposure increases antimicrobial resistance and has also been associated with long-term harms, including allergies, inflammatory diseases and weight gain. We assessed antibiotic exposure in the first 2 years of life in Australian children, the factors influencing this and its appropriateness. METHODS: Data from 1201 participants in the MIS BAIR randomized controlled trial were used. Multivariable logistic regression was used to identify factors associated with antibiotic exposure. RESULTS: At 1 and 2 years of age, exposure to at least one course of antibiotics was 43% and 67%, with the highest first antibiotic prescription rate between 9 and 18 months. Amoxicillin was the most frequently used antibiotic (59%), followed by cefalexin (7%). The most common diagnoses for which antibiotics were prescribed were respiratory tract infections from 0 to 6 months of age and otitis media from 6 to 12 months. Factors associated with antibiotic exposure from 0 to 12 months of age were delivery by Caesarean section (adjusted odd-ratio (aOR) 1.5, 95%CI 1.1-1.9), birth in winter (aOR 1.7, 95%CI 1.2-2.4), maternal antibiotic exposure during the last trimester of pregnancy (aOR 1.6, 95%CI 1.1-2.3), cessation of breastfeeding by 6 months of age (aOR 1.5, 95%CI 1.1-2.0) and day-care attendance (aOR 1.4, 95%CI 1.1-1.8). Based on parent-reported questionnaires, 27% of infants were treated in the first year of life for conditions unlikely to need antibiotic treatment. CONCLUSION: At least two-thirds of children were prescribed antibiotics in the first 2 years of life, and more than a quarter of these exposures may have been unnecessary.

Neonatal BCG Vaccination for Prevention of Allergy in Infants: The MIS BAIR Randomised Controlled Trial.

BACKGROUND: The beneficial off-target effects of Bacille Calmette-Guérin (BCG) vaccination potentially include protection against allergy. OBJECTIVE: In the MIS BAIR trial, we aimed to determine whether neonatal BCG vaccination reduces atopic sensitisation and clinical food allergy in infants. METHODS: In this randomised controlled trial, 1272 neonates were allocated to BCG-Denmark vaccine (0.05 mL intradermal dose) or no BCG at birth. Randomisation was stratified by recruitment site, mode of delivery and plurality of birth. The primary outcome was the incidence of atopic sensitisation determined by skin prick test at 1 year of age. Food allergy was determined by 3-monthly online questionnaires and oral food challenges. Data were analysed by intention-to-treat using binary regression. CLINICALTRIALS: gov (NCT01906853). RESULTS: Atopic sensitisation during the first year of life was 22.9% among infants in the BCG group and 18.9% in the control group (adjusted risk difference (aRD) 3.8% (95% CI -1.5 to 9.1) after multiple imputation). Clinical food allergy was similar between infants in the BCG and control groups (9.8% vs. 9.6%; aRD 0.2, 95% CI -3.4 to 3.8). An interaction was observed between the primary outcome and maternal history of BCG vaccination. No interaction was observed for the additional prespecified potential effect modifiers tested (sex, delivery mode, family history of any allergy, season of birth, hepatitis B vaccination at randomisation, BCG scar and age at BCG administration). CONCLUSIONS AND CLINICAL RELEVANCE: Neonatal BCG-Denmark vaccination does not protect against atopic sensitisation or clinical food allergy in the first year of life.

Interpreting the Results of Trials of BCG Vaccination for Protection Against COVID-19.

BCG vaccination has beneficial off-target ("nonspecific") effects on nonmycobacterial infections. On this premise, trials set out to investigate whether BCG provides off-target protection against coronavirus disease 2019 (COVID-19). A literature search identified 11 randomized "BCG COVID-19" trials, with conflicting results. These trials and the differences in their study design are discussed using the PICOT (participants, intervention, control, outcome, and timing) framework to highlight the factors that likely explain their inconsistent findings. These include participant age, sex and comorbid conditions, BCG vaccination strain and dose, outcome measure and duration of follow-up. Understanding how to control these factors to best exploit BCG's off-target effects will be important in designing future trials and intervention strategies.

Bacillus Calmette-Guérin Skin Reaction Predicts Enhanced Mycobacteria-Specific T-Cell Responses in Infants: A Post Hoc Analysis of a Randomized Controlled Trial.

Rationale: Scar formation following bacillus Calmette-Guérin (BCG) vaccination has been associated with lower all-cause mortality; the relation between scar and mycobacteria-specific protection against tuberculosis is debated. Objectives: To evaluate the association between BCG skin reaction and mycobacteria-specific immune responses. Methods: A post hoc analysis was done among 214 infants in Australia randomized to vaccination with one of three BCG vaccine strains (BCG-Denmark, BCG-Japan, or BCG-Russia) given at birth or BCG-Denmark given at 2 months of age. Measurements and Main Results: BCG skin reaction size and characteristics 10 weeks after vaccination were related to the in vitro mycobacteria-specific immune responses measured in stimulated whole blood. The size and characteristics of the skin reaction correlated positively with in vitro immune responses, even after adjusting for BCG vaccine strain and age at vaccination. Specifically, the reaction size and characteristics correlated with the proportion of mycobacteria-specific polyfunctional CD4+ T cells after stimulation with BCG and PPD and, to a lesser extent, after stimulation with Mycobacterium tuberculosis or Mycobacterium ulcerans. A similar correlation was observed with concentrations of IFN-γ, IL-2, tumor necrosis factor, and IL-13 in the supernatant after stimulation with BCG, PPD, and M. tuberculosis and to some degree for the proportions of mycobacteria-specific polyfunctional CD8+ T cells and CD107+ cytotoxic cells. Conclusions: BCG skin reaction correlated with the magnitude of mycobacteria-specific T-cell responses. As T-cell responses play a key role in defense against mycobacteria, the relationship between BCG scar formation and protection against tuberculosis should be revisited. This may also extend to the need for BCG revaccination in scar-negative individuals.Clinical trial registered with www.australianclinicaltrials.gov.au/clinical-trial-registries (ACTRN12608000227392).

Prevention of infant eczema by neonatal Bacillus Calmette-Guérin vaccination: The MIS BAIR randomized controlled trial.

BACKGROUND: Bacille Calmette-Guérin (BCG) vaccine could play a role in counteracting the rising prevalence of atopic diseases, through its beneficial off-target effects. We aimed to determine whether neonatal BCG vaccination reduces the incidence of eczema in infants. METHODS: Randomized controlled trial with 1272 infants allocated to receive BCG-Denmark or no BCG at birth. The primary outcome was the 12-month incidence of eczema based on 3-monthly questionnaires. Eczema was also assessed at a 12-month clinic visit. ClinicalTrial.gov: NCT01906853. RESULTS: The 12-month eczema incidence was 32.2% in the BCG group compared with 36.6% in the control group (adjusted risk difference (aRD) -4.3%, 95% CI -9.9% to 1.3%, multiple imputation model). In addition, comparing infants in the BCG group with the control group, 15.7% vs. 19.2% had eczema lesions at the 12-month visit (aRD -3.5%, 95% CI -8.0% to 1.0%); 35.7% vs. 39.0% reported using topical steroids (aRD -3.3, 95% CI -9.2 to 2.7); and 7.3% vs. 10.2% had severe eczema scores (aRD -3.0%, 95% CI -8.8% to 2.7%). In 344 high-risk infants (two atopic parents), the 12-month eczema incidence was 35.3% in the BCG group compared with 46.8% in the control group (aRD -11.5%, 95% CI -21.9% to -1.2%; number needed to treat 8.7, 95% CI 4.6 to 83.3). CONCLUSION: There is insufficient evidence to recommend neonatal BCG vaccination in all infants for the prevention of eczema in the first year of life; however, a modest beneficial effect was observed among high-risk infants. A single dose of BCG-Denmark soon after birth could reduce the incidence of eczema in infants with two atopic parents.

Neonatal Bacille Calmette-Guérin Vaccination and Infections in the First Year of Life: The MIS BAIR Randomized Controlled Trial.

BACKGROUND: Bacille Calmette-Guérin (BCG) vaccination has beneficial off-target effects that may include protecting against non-mycobacterial infectious diseases. We aimed to determine whether neonatal BCG vaccination reduces lower respiratory tract infections (LRTI) in infants in the Melbourne Infant Study: BCG for Allergy and Infection Reduction (MIS BAIR) trial. METHODS: In this investigator-blinded trial, neonates in Australia were randomized to receive BCG-Denmark vaccination or no BCG at birth. Episodes of LRTI were determined by symptoms reported in parent-completed, 3-month questionnaires over the first year of life. Data were analyzed by intention-to-treat using binary regression. RESULTS: A total of 1272 neonates were randomized to the BCG vaccination (n = 637) or control (n = 635) group. The proportion of participants with an episode of LRTI in the first year of life among BCG-vaccinated infants was 54.8% compared to 58.0% in the control group, resulting in a risk difference of -3.2 (95% confidence interval, -9.0 to 2.6) after multiple imputation. There was no interaction observed between the primary outcome and sex, maternal BCG, or the other prespecified effect modifiers. CONCLUSIONS: Based on the findings of this trial, there is insufficient evidence to support the use of neonatal BCG vaccination to prevent LRTI in the first year of life in high-income settings.

Constitutive type I interferon modulates homeostatic balance through tonic signaling.

Interferons (IFNs) were discovered as cytokines induced during and protecting from viral infection. They have been documented to play essential roles in numerous physiological processes beyond antiviral and antimicrobial defense, including immunomodulation, cell cycle regulation, cell survival, and cell differentiation. Recent data have also uncovered a potentially darker side to IFN, including roles in inflammatory diseases, such as autoimmunity and diabetes. IFN can have effects in the absence of acute infection, highlighting a physiologic role for constitutive IFN. Type I IFNs are constitutively produced at vanishingly low quantities and yet exert profound effects, mediated in part through modulation of signaling intermediates required for responses to diverse cytokines. We review evidence for a yin-yang of IFN function through its role in modulating crosstalk between multiple cytokines by both feedforward and feedback regulation of common signaling intermediates and postulate a homeostatic role for IFN through tonic signaling in the absence of acute infection.

Neonatal BCG Vaccination Reduces Interferon-γ Responsiveness to Heterologous Pathogens in Infants From a Randomized Controlled Trial.

BACKGROUND: BCG vaccination has beneficial nonspecific (heterologous) effects that protect against nonmycobacterial infections. We have previously reported that BCG vaccination at birth alters in vitro cytokine responses to heterologous stimulants in the neonatal period. This study investigated heterologous responses in 167 infants in the same trial 7 months after randomization. METHODS: A whole-blood assay was used to interrogate in vitro cytokine responses to heterologous stimulants (killed pathogens) and Toll-like receptor (TLR) ligands. RESULTS: Compared to BCG-naive infants, BCG-vaccinated infants had increased production of interferon gamma (IFN-γ) and monokine induced by gamma interferon (MIG) (CXCL9) in response to mycobacterial stimulation and decreased production of IFN-γ in response to heterologous stimulation and TLR ligands. Reduced IFN-γ responses were attributable to a decrease in the proportion of infants who mounted a detectable IFN-γ response. BCG-vaccinated infants also had increased production of MIG (CXCL9) and interleukin-8 (IL-8), and decreased production of IL-10, macrophage inflammatory protein-1α (MIP-1α), and MIP-1ß, the pattern of which varied by stimulant. IL-1Ra responses following TLR1/2 (Pam3CYSK4) stimulation were increased in BCG-vaccinated infants. Both sex and maternal BCG vaccination status influenced the effect of neonatal BCG vaccination. CONCLUSIONS: BCG vaccination leads to changes in IFN-γ responsiveness to heterologous stimulation. BCG-induced changes in other cytokine responses to heterologous stimulation vary by pathogen.

Association between the intestinal microbiota and allergic sensitization, eczema, and asthma: A systematic review.

The intestinal microbiota plays an important role in development of the immune system and regulation of immune responses. This review summarizes the association between the intestinal microbiota and the development of allergic sensitization, eczema, and asthma in neonates and children. Overall, a greater relative abundance of Bacteroidaceae, Clostridiaceae, and Enterobacteriaceae and a lower relative abundance of Bifidobacteriaceae and Lactobacillaceae is associated with the development of allergic sensitization, eczema, or asthma. Reduced bacterial diversity can be associated with the development of allergic disease. The association between the composition of the intestinal microbiota and the development of allergic disease or asthma is less consistent in older children than in neonates, suggesting that early-life microbial exposure plays a more important role. Inconsistencies in the results reported from different studies might partly be explained by heterogeneity in design, study populations, diagnostic criteria, microbiota analysis methods, and reporting on different taxonomic levels. Larger studies that better account for antenatal and postnatal factors will further help determine specific microbial intestinal signatures associated with increased risk of allergy and asthma. This will enable the early identification of infants at high risk and facilitate novel strategies and interventions to prevent and treat these conditions, including modifying the intestinal microbiota early in life.

Neonatal BCG Vaccination Influences Cytokine Responses to Toll-like Receptor Ligands and Heterologous Antigens.

Background: BCG vaccination is associated with a reduction in all-cause infant mortality in high-mortality settings. The underlying mechanisms remain uncertain, but long-term modulation of the innate immune response (trained immunity) may be involved. Methods: Whole-blood specimens, collected 7 days after randomization from 212 neonates enrolled in a randomized trial of neonatal BCG vaccination, were stimulated with killed pathogens and Toll-like receptor (TLR) ligands to interrogate cytokine responses. Results: BCG-vaccinated infants had increased production of interleukin 6 (IL-6) in unstimulated samples and decreased production of interleukin 1 receptor antagonist, IL-6, and IL-10 and the chemokines macrophage inflammatory protein 1α (MIP-1α), MIP-1ß, and monocyte chemoattractant protein 1 (MCP-1) following stimulation with peptidoglycan (TLR2) and R848 (TLR7/8). BCG-vaccinated infants also had decreased MCP-1 responses following stimulation with heterologous pathogens. Sex and maternal BCG vaccination status interacted with neonatal BCG vaccination. Conclusions: Neonatal BCG vaccination influences cytokine responses to TLR ligands and heterologous pathogens. This effect is characterized by decreased antiinflammatory cytokine and chemokine responses in the context of higher levels of IL-6 in unstimulated samples. This supports the hypothesis that BCG vaccination modulates the innate immune system. Further research is warranted to determine whether there is an association between these findings and the beneficial nonspecific (heterologous) effects of BCG vaccine on all-cause mortality.

The NF-κB transcription factor RelA is required for the tolerogenic function of Foxp3(+) regulatory T cells.

The properties of CD4(+) regulatory T cell (Treg) subsets are dictated by distinct patterns of gene expression determined by FOXP3 and different combinations of various transcription factors. Here we show the NF-κB transcription factor RelA is constitutively active in naïve and effector Tregs. The conditional inactivation of Rela in murine FOXP3(+) cells induces a rapid onset, multi-focal autoimmune disease that depends on RelA being expressed in conventional T cells. In addition to promoting Treg lineage stability, RelA determines the size of the effector Treg population, a function influenced by the presence or absence of RelA in conventional T cells. These findings showing that RelA controls Treg stability and promotes the competitive fitness of effector Tregs highlight the importance of RelA activity in peripheral Treg induced tolerance.

The Effect of Bacille Calmette-Guérin Vaccination on the Composition of the Intestinal Microbiome in Neonates From the MIS BAIR Trial.

INTRODUCTION: The early-life intestinal microbiome plays an important role in the development and regulation of the immune system. It is unknown whether the administration of vaccines influences the composition of the intestinal microbiome. OBJECTIVE: To investigate whether Bacille Calmette-Guérin (BCG) vaccine given in the first few days of life influences the abundance of bacterial taxa and metabolic pathways in the intestinal microbiome at 1 week of age. METHODS: Healthy, term-born neonates were randomized at birth to receive BCG or no vaccine within the first few days of life. Stool samples were collected at 1 week of age from 335 neonates and analyzed using shotgun metagenomic sequencing and functional analyses. RESULTS: The composition of the intestinal microbiome was different between neonates born by cesarean section (CS) and those born vaginally. Differences in the composition between BCG-vaccinated and BCG-naïve neonates were only minimal. CS-born BCG-vaccinated neonates had a higher abundance of Staphylococcus lugdunensis compared with CS-born BCG-naïve neonates. The latter had a higher abundance of Streptococcus infantis and Trabulsiella guamensis . Vaginally-born BCG-vaccinated neonates had a higher abundance of Clostridiaceae and Streptococcus parasanguinis compared with vaginally-born BCG-naïve neonates, and a lower abundance of Veillonella atypica and Butyricimonas faecalis. Metabolic pathways that were differently abundant between BCG-vaccinated and BCG-naïve neonates were mainly those involved in sugar degradation and nucleotide/nucleoside biosynthesis. CONCLUSION: BCG given in the first few days of life has little effect on the composition of the intestinal microbiome at 1 week of age but does influence the abundance of certain metabolic pathways.

Specific and off-target immune responses following COVID-19 vaccination with ChAdOx1-S and BNT162b2 vaccines-an exploratory sub-study of the BRACE trial.

BACKGROUND: The COVID-19 pandemic led to the rapid development and deployment of several highly effective vaccines against SARS-CoV-2. Recent studies suggest that these vaccines may also have off-target effects on the immune system. We sought to determine and compare the off-target effects of the adenovirus vector ChAdOx1-S (Oxford-AstraZeneca) and modified mRNA BNT162b2 (Pfizer-BioNTech) vaccines on immune responses to unrelated pathogens. METHODS: Prospective sub-study within the BRACE trial. Blood samples were collected from 284 healthcare workers before and 28 days after ChAdOx1-S or BNT162b2 vaccination. SARS-CoV-2-specific antibodies were measured using ELISA, and whole blood cytokine responses to specific (SARS-CoV-2) and unrelated pathogen stimulation were measured by multiplex bead array. FINDINGS: Both vaccines induced robust SARS-CoV-2 specific antibody and cytokine responses. ChAdOx1-S vaccination increased cytokine responses to heat-killed (HK) Candida albicans and HK Staphylococcus aureus and decreased cytokine responses to HK Escherichia coli and BCG. BNT162b2 vaccination decreased cytokine response to HK E. coli and had variable effects on cytokine responses to BCG and resiquimod (R848). After the second vaccine dose, BNT162b2 recipients had greater specific and off-target cytokine responses than ChAdOx1-S recipients. INTERPRETATION: ChAdOx1-S and BNT162b2 vaccines alter cytokine responses to unrelated pathogens, indicative of potential off-target effects. The specific and off-target effects of these vaccines differ in their magnitude and breadth. The clinical relevance of these findings is uncertain and needs further study. FUNDING: Bill & Melinda Gates Foundation, National Health and Medical Research Council, Swiss National Science Foundation and the Melbourne Children's. BRACE trial funding is detailed in acknowledgements.

Factors influencing adverse events following COVID-19 vaccination.

Various novel platform technologies have been used for the development of COVID-19 vaccines. In this nested cohort study among healthcare workers in Australia and Brazil who received three different COVID-19-specific vaccines, we (a) evaluated the incidence of adverse events following immunization (AEFI); (b) compared AEFI by vaccine type, dose and country; (c) identified factors influencing the incidence of AEFI; and (d) assessed the association between reactogenicity and vaccine anti-spike IgG antibody responses. Of 1302 participants who received homologous 2-dose regimens of ChAdOx1-S (Oxford-AstraZeneca), BNT162b2 (Pfizer-BioNTech) or CoronaVac (Sinovac), 1219 (94%) completed vaccine reaction questionnaires. Following the first vaccine dose, the incidence of any systemic reaction was higher in ChAdOx1-S recipients (374/806, 46%) compared with BNT162b2 (55/151, 36%; p = 0.02) or CoronaVac (26/262, 10%; p < 0.001) recipients. After the second vaccine dose, the incidence of any systemic reaction was higher in BNT162b2 recipients (66/151, 44%) compared with ChAdOx1-S (164/806, 20%; p < 0.001) or CoronaVac (23/262, 9%; p < 0.001) recipients. AEFI risk was higher in younger participants, females, participants in Australia, and varied by vaccine type and dose. Prior COVID-19 did not impact the risk of AEFI. Participants in Australia compared with Brazil reported a higher incidence of any local reaction (170/231, 74% vs 222/726, 31%, p < 0.001) and any systemic reaction (171/231, 74% vs 328/726, 45%, p < 0.001), regardless of vaccine type. Following a primary course of ChAdOx1-S or CoronaVac vaccination, participants who did not report AEFI seroconverted at a similar rate to those who reported local or systemic reactions. In conclusion, we found that the incidence of AEFI was influenced by participant age and COVID-19 vaccine type, and differed between participants in Australia and Brazil.

Accelerated Bacille Calmette-Guérin reactions: More than meets the eye.

An accelerated local injection site reaction following Bacille Calmette-Guérin (BCG) vaccination has been associated with underlying active tuberculosis (TB) in high TB-prevalence settings. The clinical significance of this accelerated BCG reaction in individuals without TB symptoms, particularly in low TB-prevalence countries, is unclear. Using safety surveillance data and baseline interferon-gamma release assays (IGRA) within an international randomised trial of BCG vaccination in healthcare workers (the BRACE trial), we aimed to determine the incidence, and investigate for clinical implications, of an accelerated BCG reaction in asymptomatic adults in low and high TB-prevalence settings. An accelerated BCG reaction occurred in 755/1984 (38 %) of BCG-vaccinees. Although more frequently painful, tender, erythematous and/or swollen within the first fourteen days of vaccination, compared with non-accelerated reactions, the majority of injection site reactions were mild and did not meet criteria for an adverse event. Prior mycobacterial exposure, through prior BCG vaccination (OR 2.46, 95%CI 1.93-3.13, p < 0.001) or latent TB infection (OR 4.17, 95%CI 1.16-14.93, p = 0.03), and female sex (OR 1.27, 95%CI 1.03-1.57, p = 0.02), were key determinants for the occurrence of an accelerated BCG reaction. The development of an accelerated local reaction to BCG vaccination in an individual without prior history of BCG vaccination, should prompt consideration of further investigations for potential underlying TB infection.