Rapid Protective Effects of Early BCG on Neonatal Mortality Among Low Birth Weight Boys: Observations From Randomized Trials

The influence of neonatal BCG vaccination on in vitro cytokine responses to Plasmodium falciparum

BACKGROUND

Bacillus Calmette-Guérin (BCG) vaccination has off-target protective effects against infections unrelated to tuberculosis. Among these, murine and human studies suggest that BCG vaccination may protect against malaria. We investigated whether BCG vaccination influences neonatal in vitro cytokine responses to Plasmodium falciparum. Blood samples were collected from 108 participants in the Melbourne Infant Study BCG for Allergy and Infection Reduction (MIS BAIR) randomised controlled trial (Clinical trials registration NCT01906853, registered July 2013), seven days after randomisation to neonatal BCG (n = 66) or no BCG vaccination (BCG-naïve, n = 42). In vitro cytokine responses were measured following stimulation with P. falciparum-infected erythrocytes (PfIE) or E. coli.

RESULTS

No difference in the measured cytokines were observed between BCG-vaccinated and BCG-naïve neonates following stimulation with PfIE or E. coli. However, age at which blood was sampled was independently associated with altered cytokine responses to PfIE. Being male was also independently associated with increased TNF-a responses to both PfIE and E. coli.

CONCLUSION

These findings do not support a role for BCG vaccination in influencing in vitro neonatal cytokine responses to P. falciparum. Older neonates are more likely to develop P. falciparum-induced IFN-γ and IFN-γ-inducible chemokine responses implicated in early protection against malaria and malaria pathogenesis.

Effects of Neonatal BCG-Japan Versus BCG-Russia Vaccination on Overall Mortality and Morbidity: Randomized Controlled Trial From Guinea-Bissau (BCGSTRAIN II)

Background

Vaccination with the Danish strain of bacille Calmette-Guérin (BCG) has been associated with pronounced reductions in all-cause neonatal mortality and morbidity. Developing a skin reaction postvaccination is associated with markedly reduced mortality risk. It is unknown whether the beneficial nonspecific effects are maintained across different BCG strains.

Methods

This was an open-label randomized controlled trial in Guinea-Bissau, comparing BCG-Japan (n = 8754) versus BCG-Russia (n = 8752) for all-cause hospital admission risk by 6 weeks of age (primary outcome) and 6 months of age. Additional secondary outcomes were in-hospital case-fatality risk (CFR), all-cause mortality, and BCG skin reaction prevalence. Participants were followed through telephone calls at 6 weeks and 6 months, with a subgroup also visited at home. We assessed admission and mortality risk in Cox models providing incidence rate ratios (IRRs) and mortality rate ratios. CFR and skin reactions were assessed by binomial regression providing risk ratios. Analyses were done overall and stratified by sex.

Results

BCG strain was not associated with admission risk, the BCG-Japan/BCG-Russia IRR being 0.92 (95% confidence interval [CI], .81-1.05) by 6 weeks and 0.92 (95% CI, .82-1.02) by 6 months. By 6 months of age, there were significantly fewer BCG-Japan infants with no skin reaction (1%) than for BCG-Russia (2%), the risk ratio being 0.36 (95% CI, .16-.81). BCG-Japan skin reactions were also larger.

Conclusions

Both vaccines induced a skin reaction in almost all participants. The BCG strains had comparable effects on morbidity and mortality, but BCG-Japan was associated with more and larger skin reactions that are indicators of lower mortality risk.

Clinical Trials Registration

NCT03400878.

Does Early Childhood BCG Vaccination Improve Survival to Midlife in a Population With a Low Tuberculosis Prevalence? Quasi-experimental Evidence on Nonspecific Effects From 32 Swedish Birth Cohorts

The Bacillus Calmette-Guérin (BCG) vaccine for tuberculosis (TB) is widely used globally. Many high-income countries discontinued nationwide vaccination policies starting in the 1980s as the TB prevalence decreased. However, there is continued scientific interest in whether the general childhood immunity boost conferred by the BCG vaccination impacts adult health and mortality in low-TB contexts (known as nonspecific effects). While recent studies have found evidence of an association between BCG vaccination and survival to ages 34-45, it is unclear whether these associations are causal or driven by the unobserved characteristics of those who chose to voluntarily vaccinate. We use the abrupt discontinuation of mandatory BCG vaccination in Sweden in 1975 as a natural experiment to estimate the causal nonspecific effect of the BCG vaccine on cohort survival to midlife. Applying two complementary study designs, we find no evidence that survival to age 40 was affected by the discontinuation of childhood BCG vaccination. The results are consistent among both males and females and are robust to several sensitivity tests. Overall, despite prior correlational studies suggesting large nonspecific effects, we do not find any population-level evidence for a nonspecific effect of the BCG vaccine discontinuation on survival to age 40 in Sweden.

Association of vaccination status with the clinicobiochemical profile, hospital stay, and mortality in COVID-19: A case-control study

Background and Aims

The effectiveness of coronavirus disease 2019 (COVID-19) vaccines in reducing symptoms, disease advancement, complications, and mortality in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been well-established. This case-control study aimed to compare different blood parameters, and prognostic and survival outcomes of COVID-19 patients based on vaccination status.

Methods

We performed a case-control study that included hospitalized patients with COVID-19 at Tribhuvan University Teaching Hospital, Kathmandu, Nepal. Individuals who received vaccination were designated as cases and unvaccinated individuals as controls. Demographics, co-morbidity, clinical data, laboratory data, and disease outcomes were recorded for both groups. Multivariate, Cox, and linear regression were used for analysing blood parameters, hospital admission, survival, and hospital stay, respectively, between cases and controls.

Results

Out of 100 participants enrolled, 46 were vaccinated, and 54 weren't. At admission, ferritin and erythrocyte sedimentation rate (ESR) were significantly lower in cases. At discharge, cases showed a higher monocyte than controls. Ferritin, ESR, and d-imer showed excellent performance in determining the severity of symptoms. Significant correlation and regression of ferritin and ESR with the length of hospital stay was observed. Length of hospital stay was significantly lower in cases than in controls. No significant differences between cases and controls were observed in mortality.

Conclusion

COVID-19 vaccines effectively reduced hospitalization duration. Ferritin and ESR were significantly lower in vaccinated individuals and showed the best utility in monitoring the disease.

Erratum: Factors influencing scar formation following Bacille Calmette-Guérin (BCG) vaccination

[This corrects the article DOI: 10.1016/j.heliyon.2023.e15241.].

Sarcoidosis rates in BCG-vaccinated and unvaccinated young adults: A natural experiment using Danish registers

OBJECTIVES

Sarcoidosis may have an infectious trigger, including Mycobacterium spp. The Bacille Calmette-Guérin (BCG) vaccine provides partial protection against tuberculosis and induces trained immunity. We examined the incidence rate (IR) of sarcoidosis in Danish individuals born during high BCG vaccine uptake (born before 1976) compared with individuals born during low BCG vaccine uptake (born in or after 1976).

METHODS

We performed a quasi-randomized registry-based incidence study using data from the Danish Civil Registration System and the Danish National Patient Registry between 1995 and 2016. We included individuals aged 25-35 years old and born between 1970 and 1981. Using Poisson regression models, we calculated the incidence rate ratio (IRR) of sarcoidosis in individuals born during low BCG vaccine uptake versus high BCG vaccine uptake, adjusting for age and calendar year (separately for men and women).

RESULTS

The IR of sarcoidosis was increased for individuals born during low BCG vaccine uptake compared with individuals born during high BCG vaccine uptake, which was largely attributed to men. The IRR of sarcoidosis for men born during low BCG vaccine uptake versus high BCG vaccine uptake was 1.22 (95% confidence interval [CI] 1.02-1.45). In women, the IRR was 1.08 (95% CI 0.88-1.31).

CONCLUSION

In this quasi-experimental study that minimizes confounding, the time period with high BCG vaccine uptake was associated with a lower incidence rate of sarcoidosis in men, with a similar effect seen in women that did not reach significance. Our findings support a potential protective effect of BCG vaccination against the development of sarcoidosis. Future interventional studies for high-risk individuals could be considered.

Factors influencing scar formation following Bacille Calmette-Guérin (BCG) vaccination

The prevalence of scar formation following Bacille Calmette-Guérin (BCG) vaccination varies globally. The beneficial off-target effects of BCG are proposed to be stronger amongst children who develop a BCG scar. Within an international randomised trial ('BCG vaccination to reduce the impact of coronavirus disease 2019 (COVID-19) in healthcare workers'; BRACE Trial), this nested prospective cohort study assessed the prevalence of and factors influencing scar formation, as well as participant perception of BCG scarring 12 months following vaccination . Amongst 3071 BCG-recipients, 2341 (76%) developed a BCG scar. Scar prevalence was lowest in Spain and highest in UK. Absence of post-injection wheal (OR 0.4, 95%CI 0.2-0.9), BCG revaccination (OR 1.7, 95%CI 1.3-2.0), female sex (OR 2.0, 95%CI 1.7-2.4), older age (OR 0.4, 95%CI 0.4-0.5) and study country (Brazil OR 1.6, 95%CI 1.3-2.0) influenced BCG scar prevalence. Of the 2341 participants with a BCG scar, 1806 (77%) did not mind having the scar. Participants more likely to not mind were those in Brazil, males and those with a prior BCG vaccination history. The majority (96%) did not regret having the vaccine. Both vaccination-related (amenable to optimisation) and individual-related factors affected BCG scar prevalence 12 months following BCG vaccination of adults, with implications for maximising the effectiveness of BCG vaccination.

Training vs. Tolerance: The Yin/Yang of the Innate Immune System

For almost nearly a century, memory functions have been attributed only to acquired immune cells. Lately, this paradigm has been challenged by an increasing number of studies revealing that innate immune cells are capable of exhibiting memory-like features resulting in increased responsiveness to subsequent challenges, a process known as trained immunity (known also as innate memory). In contrast, the refractory state of endotoxin tolerance has been defined as an immunosuppressive state of myeloid cells portrayed by a significant reduction in the inflammatory capacity. Both training as well tolerance as adaptive features are reported to be accompanied by epigenetic and metabolic alterations occurring in cells. While training conveys proper protection against secondary infections, the induction of endotoxin tolerance promotes repairing mechanisms in the cells. Consequently, the inappropriate induction of these adaptive cues may trigger maladaptive effects, promoting an increased susceptibility to secondary infections—tolerance, or contribute to the progression of the inflammatory disorder—trained immunity. This review aims at the discussion of these opposing manners of innate immune and non-immune cells, describing the molecular, metabolic and epigenetic mechanisms involved and interpreting the clinical implications in various inflammatory pathologies.

Sex and Gender Differences in Tuberculosis Pathogenesis and Treatment Outcomes

Tuberculosis remains a daunting public health concern in many countries of the world. A consistent observation in the global epidemiology of tuberculosis is an excess of cases of active pulmonary tuberculosis among males compared with females. Data from both humans and animals also suggest that males are more susceptible than females to develop active pulmonary disease. Similarly, male sex has been associated with poor treatment outcomes. Despite this growing body of evidence, little is known about the mechanisms driving sex bias in tuberculosis disease. Two dominant hypotheses have been proposed to explain the predominance of active pulmonary tuberculosis among males. The first is based on the contribution of biological factors, such as sex hormones and genetic factors, on host immunity during tuberculosis. The second is focused on non-biological factors such as smoking, professional exposure, and health-seeking behaviors, known to be influenced by gender. In this chapter, we review the literature regarding these two prevailing hypotheses by presenting human but also experimental animal studies. In addition, we presented studies aiming at examining the impact of sex and gender on other clinical forms of tuberculosis such as latent tuberculosis infection and extrapulmonary tuberculosis, which both appear to have their own specificities in relation to sex. We also highlighted potential intersections between sex and gender in the context of tuberculosis and shared future directions that could guide in elucidating mechanisms of sex-based differences in tuberculosis pathogenesis and treatment outcomes.

Sex-Differential and Non-specific Effects of Vaccines Over the Life Course

Biological sex and age have profound effects on immune responses throughout the lifespan and impact vaccine acceptance, responses, and outcomes. Mounting evidence from epidemiological, clinical, and animal model studies show that males and females respond differentially to vaccination throughout the lifespan. Within age groups, females tend to produce greater vaccine-induced immune responses than males, with sex differences apparent across all age groups, but are most pronounced among reproductive aged individuals. Females report more adverse effects following vaccination than males. Females, especially among children under 5 years of age, also experience more non-specific effects of vaccination. Despite these known sex- and age-specific differences in vaccine-induced immune responses and outcomes, sex and age are often ignored in vaccine research. Herein, we review the known sex differences in the immunogenicity, effectiveness, reactogenicity, and non-specific effects of vaccination over the lifespan. Ways in which these data can be leveraged to improve vaccine research are described.

Neonatal Bacillus Calmette-Guérin Vaccination to Prevent Early-Life Eczema: A Systematic Review and Meta-analysis

ABSTRACT

Increasing evidence suggests that early-life bacillus Calmette-Guérin (BCG) vaccine could prevent atopic eczema through its beneficial off-target effects. In this meta-analysis, 3 randomized control trials with similar methods were included and enabled robust estimations with low heterogeneity, involving a total of 5655 children randomized to early-life BCG Denmark (n = 2832) or no BCG (n = 2823). Meta-analyses suggest a beneficial effect of BCG to prevent eczema (risk ratio [RR], 0.89; 95% confidence interval [CI], 0.82-0.98). In subgroup analyses, BCG was more beneficial in boys (RR, 0.84; 95% CI, 0.74-0.95) and in children born to 2 atopic parents (RR, 0.81; 95% CI, 0.68-0.97). The NNT to prevent one case of eczema among children of 1 or 2 atopic parent was 20 (95% CI, 12-50). Bacillus Calmette-Guérin Denmark leads to an 11% reduction in the risk of eczema in early life. A greater effect was observed with increasing predisposition. Given its well-established safety profile, neonatal BCG vaccination should be considered for children of atopic parents.

Infant BCG vaccination and risk of pulmonary and extrapulmonary tuberculosis throughout the life course: a systematic review and individual participant data meta-analysis

BACKGROUND

BCG vaccines are given to more than 100 million children every year, but there is considerable debate regarding the effectiveness of BCG vaccination in preventing tuberculosis and death, particularly among older children and adults. We therefore aimed to investigate the age-specific impact of infant BCG vaccination on tuberculosis (pulmonary and extrapulmonary) development and mortality.

METHODS

In this systematic review and individual participant data meta-analysis, we searched MEDLINE, Web of Science, BIOSIS, and Embase without language restrictions for case-contact cohort studies of tuberculosis contacts published between Jan 1, 1998, and April 7, 2018. Search terms included "mycobacterium tuberculosis", "TB", "tuberculosis", and "contact". We excluded cohort studies that did not provide information on BCG vaccination or were done in countries that did not recommend BCG vaccination at birth. Individual-level participant data for a prespecified list of variables, including the characteristics of the exposed participant (contact), the index case, and the environment, were requested from authors of all eligible studies. Our primary outcome was a composite of prevalent (diagnosed at or within 90 days of baseline) and incident (diagnosed more than 90 days after baseline) tuberculosis in contacts exposed to tuberculosis. Secondary outcomes were pulmonary tuberculosis, extrapulmonary tuberculosis, and mortality. We derived adjusted odds ratios (aORs) using mixed-effects, binary, multivariable logistic regression analyses with study-level random effects, adjusting for the variable of interest, baseline age, sex, previous tuberculosis, and whether data were collected prospectively or retrospectively. We stratified our results by contact age and Mycobacterium tuberculosis infection status. This study is registered with PROSPERO, CRD42020180512.

FINDINGS

We identified 14 927 original records from our database searches. We included participant-level data from 26 cohort studies done in 17 countries in our meta-analysis. Among 68 552 participants, 1782 (2·6%) developed tuberculosis (1309 [2·6%] of 49 686 BCG-vaccinated participants vs 473 [2·5%] of 18 866 unvaccinated participants). The overall effectiveness of BCG vaccination against all tuberculosis was 18% (aOR 0·82, 95% CI 0·74-0·91). When stratified by age, BCG vaccination only significantly protected against all tuberculosis in children younger than 5 years (aOR 0·63, 95% CI 0·49-0·81). Among contacts with a positive tuberculin skin test or IFNγ release assay, BCG vaccination significantly protected against tuberculosis among all participants (aOR 0·81, 95% CI 0·69-0·96), participants younger than 5 years (0·68, 0·47-0·97), and participants aged 5-9 years (0·62, 0·38-0·99). There was no protective effect among those with negative tests, unless they were younger than 5 years (0·54, 0·32-0·90). 14 cohorts reported on whether tuberculosis was pulmonary or extrapulmonary (n=57 421). BCG vaccination significantly protected against pulmonary tuberculosis among all participants (916 [2·2%] in 41 119 vaccinated participants vs 334 [2·1%] in 16 161 unvaccinated participants; aOR 0·81, 0·70-0·94) but not against extrapulmonary tuberculosis (106 [0·3%] in 40 318 vaccinated participants vs 38 [0·2%] in 15 865 unvaccinated participants; 0·96, 0·65-1·41). In the four studies with mortality data, BCG vaccination was significantly protective against death (0·25, 0·13-0·49).

INTERPRETATION

Our results suggest that BCG vaccination at birth is effective at preventing tuberculosis in young children but is ineffective in adolescents and adults. Immunoprotection therefore needs to be boosted in older populations.

FUNDING

National Institutes of Health.

A place for neutrophils in the beneficial pathogen-agnostic effects of the BCG vaccine

The BCG vaccine has long been recognized for reducing the risk to suffer from infectious diseases unrelated to its target disease, tuberculosis. Evidence from human trials demonstrate substantial reductions in all-cause mortality, especially in the first week of life. Observational studies have identified an association between BCG vaccination and reduced risk of respiratory infectious disease and clinical malaria later in childhood. The mechanistic basis for these pathogen-agnostic benefits, also known as beneficial non-specific effects (NSE) of BCG have been attributed to trained immunity, or epigenetic reprogramming of hematopoietic cells that give rise to innate immune cells responding more efficiently to a broad range of pathogens. Furthermore, within trained immunity, the focus so far has been on enhanced monocyte function. However, polymorphonuclear cells, namely neutrophils, are not only major constituents of the hematopoietic compartment but functionally as well as numerically represent a prominent component of the immune system. The beneficial NSEs of the BCG vaccine on newborn sepsis was recently demonstrated to be driven by a BCG-mediated numeric increase of neutrophils (emergency granulopoiesis (EG)). And experimental evidence in animal models suggest that BCG can modulate neutrophil function as well. Together, these findings suggest that neutrophils are crucial to at least the immediate beneficial NSE of the BCG vaccine. Efforts to uncover the full gamut of mechanisms underpinning the broad beneficial effects of BCG should therefore include neutrophils at the forefront.

Innate Immune Memory and the Host Response to Infection

Unlike the adaptive immune system, the innate immune system has classically been characterized as being devoid of memory functions. However, recent research shows that innate myeloid and lymphoid cells have the ability to retain memory of prior pathogen exposure and become primed to elicit a robust, broad-spectrum response to subsequent infection. This phenomenon has been termed innate immune memory or trained immunity. Innate immune memory is induced via activation of pattern recognition receptors and the actions of cytokines on hematopoietic progenitors and stem cells in bone marrow and innate leukocytes in the periphery. The trained phenotype is induced and sustained via epigenetic modifications that reprogram transcriptional patterns and metabolism. These modifications augment antimicrobial functions, such as leukocyte expansion, chemotaxis, phagocytosis, and microbial killing, to facilitate an augmented host response to infection. Alternatively, innate immune memory may contribute to the pathogenesis of chronic diseases, such as atherosclerosis and Alzheimer's disease.

Single-cell RNA sequencing reveals induction of distinct trained immunity programs in human monocytes

Trained immunity refers to the long-lasting memory traits of innate immunity. Recent studies have shown that trained immunity is orchestrated by sustained changes in epigenetic marks and metabolic pathways, leading to an altered transcriptional response towards a second challenge. However, the potential heterogeneity of trained immunity induction in innate immune cells has not been explored. In this study, we demonstrate cellular transcriptional programs to four different inducers of trained immunity in monocyte populations at single-cell resolution. Specifically, we identified three monocyte subpopulations upon the induction of trained immunity, and replicated these findings in an in vivo study. In addition, we found gene signatures consistent with these functional programs in ulcerative colitis, sepsis and COVID-19 patients, suggesting the impact of trained immunity programs in immune-mediated diseases.

Does maternal BCG prime for enhanced beneficial effects of neonatal BCG in the offspring?

OBJECTIVES

Bacille Calmette-Guérin (BCG) vaccination lowers the risk of severe infection; we tested whether effects are modulated by maternal BCG in a large cohort of BCG-vaccinated newborns from Guinea-Bissau.

METHODS

Maternal BCG scar status were inspected at enrolment in a BCG trial conducted from 2014-17 in Bissau, Guinea-Bissau. We tested associations with background factors for potential confounding; maternal age affected effect estimates >5% and accordingly, all analyses were adjusted for maternal age. Hospitalization data was collected prospectively and assessed in Cox-models providing adjusted Incidence Rate Ratios (aIRRs). In-hospital risk of death (case-fatality) risk was assessed using binomial regression providing adjusted Risk Ratios (aRRs).

RESULTS

60% (6,309/10,598) of mothers had a scar. The maternal-scar/no-scar admission aIRR was 0.96 (0.81-1.14) from 0-6 weeks and 1.12 (0.97-1.28) for 6 weeks-3 years. The 6-week in-hospital case-fatality infection aRR was 0.59 (0.34-1.05); 0.40 (0.17-0.91) for males and 0.86 (0.38-1.94) for females. Protection was especially evident against sepsis, the overall 6-week aRR=0.49 (0.26-0.91); no effect was observed for non-infectious deaths or after 6 weeks of age. Effects were similar across BCG strains and multivariate models adjusted for socioeconomic status did not affect estimates.

CONCLUSION

Among BCG-vaccinated newborns, there was a trend for fewer in-hospital deaths from infection associated with maternal BCG priming, especially for males. Providing BCG to adults without a vaccination scar might enhance their offspring's capacity to handle severe infections.

Bacillus Calmette-Guerin 's beneficial impact on glucose metabolism: evidence for broad based applications

Bacillus Calmette-Guerin (BCG) vaccinations improve glycemic control in juvenile-onset Type I diabetes (T1D), an effect driven by restored sugar transport through aerobic glycolysis. In a pilot clinical trial, T1D, but not latent autoimmune diabetes of adults (LADA), exhibited lower blood sugars after multidose BCG. Using a glucose transport assay, monocytes from T1D subjects showed a large stimulation index with BCG exposures; LADA subjects showed minimal BCG-induced sugar responsiveness. Monocytes from T1D, type 2 diabetes (T2D), and non-diabetic controls (NDC) were all responsive in vitro to BCG by augmented sugar utilization. Adults with prior neonatal BCG vaccination show accelerated glucose transport decades later. Finally, in vivo experiments with the NOD mouse (a T1D model) and obese db/db mice (a T2D model) confirm BCG's blood-sugar-lowering and accelerated glucose metabolism with sufficient dosing. Our results suggest that BCG's benefits for glucose metabolism may be broadly applicable to T1D and T2D, but less to LADA.

•

A pilot trial of BCG vaccinations to T1D showed reduced blood sugars but not in LADA

•

Monocytes from T1D and to some degree T2D display stimulated glucose transport

•

BCG vaccinations at birth show accelerated glucose transport decades later

•

In vivo mouse models of both T1D and T2D demonstrate BCG-induced blood sugar lowering

Evaluation of non-specific effects of human rotavirus vaccination in medical risk infants

BACKGROUND

The WHO recommends research into non-specific effects of vaccination. For rotavirus vaccines, these have not yet been well established. We studied non-specific effects up to 18 months of age using data from a quasi-experimental before-after study comparing cohorts of rotavirus vaccinated and unvaccinated infants with medical risk conditions.

METHODS

Infants were enrolled at six weeks of age before and after a stepped-wedge implementation of a hospital-based risk-group rotavirus vaccination program. Other infant vaccinations were administered according to the Dutch National Immunization Program and similar in both cohorts. Non-specific effect outcomes were prospectively collected using monthly questionnaires and included acute hospitalization (excluding for acute gastroenteritis), monthly incidence of acute respiratory illness and eczema. We used time-to-event analysis and negative binomial regression to assess the effect of at least one dose of rotavirus vaccination for each of these outcomes. Findings The analysis included 496 rotavirus unvaccinated and 719 vaccinated medical risk infants. In total, 1067 (88%) were premature, 373 (31%) small for gestational age and 201 (17%) had a congenital pathology. The adjusted hazard ratio for first acute hospitalization was 0·91 (95 %CI 0·76;1·16) for rotavirus vaccinated versus unvaccinated infants. Adjusted incidence rate ratio for acute respiratory illness was 1·05 (95 %CI 0·96;1·15) and for eczema 0·89 (95 %CI 0·69;1·15).

CONCLUSION

The results suggest no, or minimal non-specific effects from rotavirus vaccination on acute hospitalization, acute respiratory illness or eczema in medical risk infants.

TRIAL REGISTRATION

as NTR5361 in the Dutch trial registry, www.trialregister.nl.

Weaker protection against tuberculosis in BCG-vaccinated male 129 S2 mice compared to females

BCG - the only available vaccine against tuberculosis (TB) - was first given to babies 100 years ago in 1921. While it is effective against TB meningitis and disseminated TB, its efficacy against pulmonary TB is variable, notably in adults and adolescents. TB remains one of the world's leading health problems, with a higher prevalence among men. Male sex is associated with increased susceptibility to Mycobacterium tuberculosis in mice, but sex-specific responses to BCG vaccination have not been examined. In this study we vaccinated TB-susceptible 129 S2 mice with BCG and challenged with low-dose M. tuberculosis H37Rv by aerosol infection. BCG was protective against TB in both sexes, as unvaccinated mice lost weight more rapidly than vaccinated ones and suffered from worse lung pathology. However, female mice were better protected than males, showing lower lung bacterial burdens and less weight loss. Overall, vaccinated female mice had increased numbers of T cells and less myeloid cells in the lungs compared to vaccinated males. Principal component analysis of measured features revealed that mice grouped according to timepoint, sex and vaccination status. The features that had the biggest impact on grouping overall included numbers of CD8 T cells, CD8 central memory T cells and CD4 T effector cells, with neutrophil and CD11b⁺GR-1^- cell numbers having a big impact at day 29. Hierarchical clustering confirmed that the main difference in global immune response was due to mouse sex, with only a few misgrouped mice. In conclusion, we found sex-specific differences in response to M. tuberculosis H37Rv -challenge in BCG-vaccinated 129 S2 mice. This highlights the need to include both male and female mice in preclinical testing of vaccine candidates.

The Effects of Trained Innate Immunity on T Cell Responses; Clinical Implications and Knowledge Gaps for Future Research

The burgeoning field of innate immune training, also called trained immunity, has given immunologists new insights into the role of innate responses in protection against infection and in modulating inflammation. Moreover, it has led to a paradigm shift in the way we think about immune memory and the interplay between innate and adaptive immune systems in conferring immunity against pathogens. Trained immunity is the term used to describe the medium-term epigenetic and metabolic reprogramming of innate immune cells in peripheral tissues or in the bone marrow stem cell niche. It is elicited by an initial challenge, followed by a significant period of rest that results in an altered response to a subsequent, unrelated challenge. Trained immunity can be associated with increased production of proinflammatory mediators, such as IL-1β, TNF and IL-6, and increased expression of markers on innate immune cells associated with antigen presentation to T cells. The microenvironment created by trained innate immune cells during the secondary challenge may have profound effects on T cell responses, such as altering the differentiation, polarisation and function of T cell subtypes, including Th17 cells. In addition, the Th1 cytokine IFN-γ plays a critical role in establishing trained immunity. In this review, we discuss the evidence that trained immunity impacts on or can be impacted by T cells. Understanding the interplay between innate immune training and how it effects adaptive immunity will give insights into how this phenomenon may affect the development or progression of disease and how it could be exploited for therapeutic interventions or to enhance vaccine efficacy.

Post-vaccination COVID-19: A case-control study and genomic analysis of 119 breakthrough infections in partially vaccinated individuals

Background

Post-vaccination infections challenge the control of the coronavirus disease 2019 (COVID-19) pandemic.

Methods

We matched 119 cases of post-vaccination severe acute respiratory syndrome coronavirus 2 infection with BNT162b2 mRNA or ChAdOx1 nCOV-19 to 476 unvaccinated patients with COVID-19 (September 2020–March 2021) according to age and sex. Differences in 60-day all-cause mortality, hospital admission, and hospital length of stay were evaluated. Phylogenetic, single-nucleotide polymorphism (SNP), and minority variant allele (MVA) full-genome sequencing analysis was performed.

Results

Overall, 116 of 119 cases developed COVID-19 post–first vaccination dose (median, 14 days). Thirteen of 119 (10.9%) cases and 158 of 476 (33.2%) controls died (P < .001), corresponding to the 4.5 number needed to treat (NNT). Multivariably, vaccination was associated with a 69.3% (95% confidence interval [CI]: 45.8 to 82.6) relative risk (RR) reduction in mortality. Similar results were seen in subgroup analysis for patients with infection onset ≥14 days after first vaccination and across vaccine subgroups. Hospital admissions (odds ratio, 0.80; 95% CI: .51 to 1.28) and length of stay (–1.89 days; 95% CI: –4.57 to 0.78) were lower for cases, while cycle threshold values were higher (30.8 vs 28.8, P = .053). B.1.1.7 was the predominant lineage in cases (100 of 108, 92.6%) and controls (341 of 446, 76.5%). Genomic analysis identified 1 post-vaccination case that harbored the E484K vaccine-escape mutation (B.1.525 lineage).

Conclusions

Previous vaccination reduces mortality when B.1.1.7 is the predominant lineage. No significant lineage-specific genomic changes during phylogenetic, SNP, and MVA analysis were detected.

Oral Polio Vaccine to Protect Against COVID-19: Out of the Box Strategies?

The global coronavirus disease 2019 pandemic has raised significant concerns of developing rapid, broad strategies to protect the vulnerable population and prevent morbidity and mortality. However, even with an aggressive approach, controlling the pandemic has been challenging, with concerns of emerging variants that likely escape vaccines, nonadherence of social distancing/preventive measures by the public, and challenges in rapid implementation of a global vaccination program that involves mass production, distribution, and execution. In this review, we revisit the utilization of attenuated vaccinations, such as the oral polio vaccine, which are safe, easy to administer, and likely provide cross-protection against respiratory pathogens. We discuss the rationale and data supporting its use and detail description of available vaccines that could be repurposed for curtailing the pandemic.

BCG-induced non-specific effects on heterologous infectious disease in Ugandan neonates: an investigator-blind randomised controlled trial

BACKGROUND

Trials done in infants with low birthweight in west Africa suggest that BCG vaccination reduces all-cause mortality in the neonatal period, probably because of heterologous protection against non-tuberculous infections. This study investigated whether BCG alters all-cause infectious disease morbidity in healthy infants in a different high-mortality setting, and explored whether the changes are mediated via trained innate immunity.

METHODS

This was an investigator-blind, randomised, controlled trial done at one hospital in Entebbe, Uganda. Infants who were born unwell (ie, those who were not well enough to be discharged directly home from the labour ward because they required medical intervention), with major congenital malformations, to mothers with HIV, into families with known or suspected tuberculosis, or for whom cord blood samples could not be taken, were excluded from the study. Any other infant well enough to be discharged directly from the labour ward was eligible for inclusion, with no limitation on gestational age or birthweight. Participants were recruited at birth and randomly assigned (1:1) to receive standard dose BCG 1331 (BCG-Danish) on the day of birth or at age 6 weeks (computer-generated randomisation, block sizes of 24, stratified by sex). Investigators and clinicians were masked to group assignment; parents were not masked. Participants were clinically followed up to age 10 weeks and contributed blood samples to one of three immunological substudies. The primary clinical outcome was physician-diagnosed non-tuberculous infectious disease incidence. Primary immunological outcomes were histone trimethylation at the promoter region of TNF, IL6, and IL1B; ex-vivo production of TNF, IL-6, IL-1β, IL-10, and IFNγ after heterologous stimulation; and transferrin saturation and hepcidin levels. All outcomes were analysed in the modified intention-to-treat population of all randomly assigned participants except those whose for whom consent was withdrawn. This trial is registered with the International Standard Randomised Controlled Trial Number registry (#59683017).

FINDINGS

Between Sept 25, 2014, and July 31, 2015, 560 participants were enrolled and randomly assigned to receive BCG at birth (n=280) or age 6 weeks (n=280). 12 participants assigned to receive BCG at birth and 11 participants assigned to receive BCG at age 6 weeks were withdrawn from the study by their parents shortly after randomisation and were not included in analyses. During the first 6 weeks of life before the infants in the delayed vaccination group received BCG vaccination, physician-diagnosed non-tuberculous infectious disease incidence was lower in infants in the BCG at birth group than in the delayed group (98 presentations in the BCG at birth group vs 129 in the delayed BCG group; hazard ratio [HR] 0·71 [95% CI 0·53-0·95], p=0·023). After BCG in the delayed group (ie, during the age 6-10 weeks follow-up), there was no significant difference in non-tuberculous infectious disease incidence between the groups (88 presentations vs 76 presentations; HR 1·10 [0·87-1·40], p=0·62). BCG at birth inhibited the increase in histone trimethylation at the TNF promoter in peripheral blood mononuclear cells occurring in the first 6 weeks of life. H3K4me3 geometric mean fold-increases were 3·1 times lower at the TNF promoter (p=0·018), 2·5 times lower at the IL6 promoter (p=0·20), and 3·1 times lower at the IL1B promoter (p=0·082) and H3K9me3 geometric mean fold-increases were 8·9 times lower at the TNF promoter (p=0·0046), 1·2 times lower at the IL6 promoter (p=0·75), and 4·6 times lower at the IL1B promoter (p=0·068), in BCG-vaccinated (BCG at birth group) versus BCG-naive (delayed BCG group) infants. No clear effect of BCG on ex-vivo production of TNF, IL-6, IL-1β, IL-10, and IFNγ after heterologous stimulation, or transferrin saturation and hepcidin concentration, was detected (geometric mean ratios between 0·68 and 1·68; p≥0·038 for all comparisons).

INTERPRETATION

BCG vaccination protects against non-tuberculous infectious disease during the neonatal period, in addition to having tuberculosis-specific effects. Prioritisation of BCG on the first day of life in high-mortality settings might have significant public-health benefits through reductions in all-cause infectious morbidity and mortality.

FUNDING

Wellcome Trust.

TRANSLATIONS

For the Luganda and Swahili translations of the abstract see Supplementary Materials section.

Neonatal BCG vaccination and infections in the first year of life: the MIS BAIR randomised 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 MIS BAIR trial.

METHODS

In this investigator-blinded trial, neonates in Australia were randomised to receive BCG-Denmark vaccination or no BCG at birth. Episodes of LRTI were determined by symptoms reported in parent-completed 3-monthly questionnaires over the first year of life. Data were analysed by intention-to-treat using binary regression. Clinicaltrials.gov (NCT01906853).

RESULTS

From August 2013 to September 2016, 1272 neonates were randomised 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% CI -9.0 to 2.6) after multiple imputation. There was no interaction observed between the primary outcome and sex, maternal BCG or the other pre-specified 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.

Epigenetic changes related to glucose metabolism in type 1 diabetes after BCG vaccinations: A vital role for KDM2B

BACKGROUND

A recent epigenome-wide association study of genes associated with type 2 diabetics (T2D), used integrative cross-omics analysis to identify 22 abnormally methylated CpG sites associated with insulin and glucose metabolism. Here, in this epigenetic analysis we preliminarily determine whether the same CpG sites identified in T2D also apply to type 1 diabetes (T1D). We then determine whether BCG vaccination could correct the abnormal methylation patterns, considering that the two diseases share metabolic derangements.

METHODS

T1D (n = 13) and control (n = 8) subjects were studied at baseline and then T1D subjects studied yearly for 3 years after receiving BCG vaccinations in a clinical trial. In this biomarker analysis, methylation patterns were evaluated on CD4+ T-lymphocytes from baseline and yearly blood samples using the human Illumina Methylation EPIC Bead Chip. Methylation analysis combined with mRNA analysis using RNAseq.

RESULTS

Broad but not complete overlap was observed between T1D and T2D in CpG sites with abnormal methylation. And in the three-year observation period after BCG vaccinations, the majority of the abnormal methylation sites were corrected in vivo. Genes of particular interest were related to oxidative phosphorylation (CPT1A, LETM1, ABCG1), to the histone lysine demethylase gene (KDM2B), and mTOR signaling through the DDIT4 gene. The highlighted CpG sites for both KDM2B and DDIT4 genes were hypomethylated at baseline compared to controls; BCG vaccination corrected the defect by hypermethylation.

CONCLUSIONS

Glycolysis is regulated by methylation of genes. This study unexpectedly identified both KDM2B and DDIT4 as genes controlling BCG-driven re-methylation of histones, and the activation of the mTOR pathway for facilitated glucose transport respectively. The BCG effect at the gene level was confirmed by reciprocal mRNA changes. The DDIT4 gene with known inhibitory role of mTOR was re-methylated after BCG, a step likely to allow improved glucose transport. BCGs driven methylation of KDM2B's site should halt augmented histone activity, a step known to allow cytokine activation and increased glycolysis.

Immediate Bacille Calmette-Guérin vaccination to neonates requiring perinatal treatment at the maternity ward in Guinea-Bissau: A randomized controlled trial

BACKGROUND

Randomized controlled trials (RCTs) indicate that Bacille Calmette-Guérin (BCG) vaccination provides broad beneficial non-specific protection against infections. We investigated the effect on in-hospital mortality of providing BCG immediately upon admission to a neonatal intensive care unit (NICU), rather than BCG-at-discharge. The pre-trial NICU mortality was 13% and we hypothesized that BCG would reduce mortality by 40%.

METHODS

Parallel-group, open-label RCT initiated in 2013 in Guinea-Bissau. NICU-admitted neonates were randomized 1:1 to BCG+Oral Polio Vaccine (OPV) immediately (intervention) versus BCG+OPV at hospital discharge (control; usual practice). The trial was discontinued due to decreasing in-hospital mortality and major NICU restructuring. We assessed overall and disease-specific mortality by randomization allocation in Cox Proportional Hazards models providing Mortality Rate Ratios (MRRs).

RESULTS

We recruited 3,353 neonates and the overall mortality was 3.1% (52/1676) for BCG-vaccinated neonates versus 3.3% (55/1677) for controls, MRR=0.94 (0.64-1.36). For non-infectious causes of death the MRR was 1.20 (0.70-2.07) and there tended to be fewer deaths from infections in the BCG group (N=14) than among controls (N=21), MRR=0.65 (0.33-1.28).

CONCLUSIONS

Providing BCG+OPV to frail neonates was safe and might protect against fatal infection in the immediate newborn period. Deaths due to prematurity and perinatal complications were unaffected by BCG.

Non-specific effects of BCG vaccination on neutrophil and lymphocyte counts of healthy neonates from a developed country

BCG vaccination is known to reduce neonatal mortality from infections in a pathogen-agnostic manner. In this observational study we report on whether an emergency granulopoietic response is elicited in term babies from a developed country following BCG vaccination. We studied a cohort of neonates re-admitted to the hospital from home for feeding support separated into 2 groups dependent on whether they had received BCG vaccination. Clinical data including gender, weight, gestational age, method of feeding and full blood count results were retrieved retrospectively. While lymphocyte counts increase following BCG vaccination irrespective of gender and in proportion with the time elapsed after vaccination, the increase in neutrophil counts, is only observed in boys. This increase appears to be temporary. Our results confirm the presence of emergency granulopoiesis following BCG vaccination in a neonatal cohort from a developed country. However, this effect appears to be gender-specific and is present only in boys.

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-1β, 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.

Circadian rhythm influences induction of trained immunity by BCG vaccination

BACKGROUNDThe antituberculosis vaccine bacillus Calmette-Guérin (BCG) reduces overall infant mortality. Induction of innate immune memory, also termed trained immunity, contributes toward protection against heterologous infections. Since immune cells display oscillations in numbers and function throughout the day, we investigated the effect of BCG administration time on the induction of trained immunity.METHODSEighteen volunteers were vaccinated with BCG at 6 pm and compared with 36 age- and sex-matched volunteers vaccinated between 8 am and 9 am. Peripheral blood mononuclear cells were stimulated with Staphylococcus aureus and Mycobacterium tuberculosis before, as well as 2 weeks and 3 months after, BCG vaccination. Cytokine production was measured to assess the induction of trained immunity and adaptive responses, respectively. Additionally, the influence of vaccination time on induction of trained immunity was studied in an independent cohort of 302 individuals vaccinated between 8 am and 12 pm with BCG.RESULTSCompared with evening vaccination, morning vaccination elicited both a stronger trained immunity and adaptive immune phenotype. In a large cohort of 302 volunteers, early morning vaccination resulted in a superior cytokine production capacity compared with later morning. A cellular, rather than soluble, substrate of the circadian effect of BCG vaccination was demonstrated by the enhanced capacity to induce trained immunity in vitro in morning- compared with evening-isolated monocytes.CONCLUSIONSBCG vaccination in the morning induces stronger trained immunity and adaptive responses compared with evening vaccination. Future studies should take vaccine administration time into account when studying specific and nonspecific effects of vaccines; early morning should be the preferred moment of BCG administration.FUNDINGThe Netherlands Organization for Scientific Research, the European Research Council, and the Danish National Research Foundation.

BCG vaccination in humans inhibits systemic inflammation in a sex-dependent manner

BACKGROUNDInduction of innate immune memory, also termed trained immunity, by the antituberculosis vaccine bacillus Calmette-Guérin (BCG) contributes to protection against heterologous infections. However, the overall impact of BCG vaccination on the inflammatory status of an individual is not known; while induction of trained immunity may suggest increased inflammation, BCG vaccination has been epidemiologically associated with a reduced incidence of inflammatory and allergic diseases.METHODSWe investigated the impact of BCG (BCG-Bulgaria, InterVax) vaccination on systemic inflammation in a cohort of 303 healthy volunteers, as well as the effect of the inflammatory status on the response to vaccination. A targeted proteome platform was used to measure circulating inflammatory proteins before and after BCG vaccination, while ex vivo Mycobacterium tuberculosis- and Staphylococcus aureus-induced cytokine responses in peripheral blood mononuclear cells were used to assess trained immunity.RESULTSWhile BCG vaccination enhanced cytokine responses to restimulation, it reduced systemic inflammation. This effect was validated in 3 smaller cohorts, and was much stronger in men than in women. In addition, baseline circulating inflammatory markers were associated with ex vivo cytokine responses (trained immunity) after BCG vaccination.CONCLUSIONThe capacity of BCG to enhance microbial responsiveness while dampening systemic inflammation should be further explored for potential therapeutic applications.FUNDINGNetherlands Organization for Scientific Research, European Research Council, and the Danish National Research Foundation.

Can what have we learnt about BCG vaccination in the last 20 years help us to design a better tuberculosis vaccine?

•

The BCG vaccine provides variable protection against tuberculosis.

•

Correlates of protection remain elusive, but IFNγ can measure immunogenicity.

•

BCG vaccination induces innate immune training as well as antigen-specific immunity.

•

Many factors may contribute to the variable responses to BCG vaccination.

•

Prior BCG vaccination or factors modulating its efficacy may affect new TB vaccines.

•

Innate training may also provide non-specific protection against infectious diseases.

•

New TB vaccines should not lose BCG's beneficial non-specific effects.

The BCG vaccine will, in 2021, have been in use for 100 years. Much remains to be understood, including the reasons for its variable efficacy against pulmonary tuberculosis in adults. This review will discuss what has been learnt about the BCG vaccine in the last two decades, and whether this new information can be exploited to improve its efficacy, by enhancing its ability to induce either antigen-specific and/or non-specific effects. Many factors affect both the immunogenicity of BCG and its protective efficacy, highlighting the challenges of working with a live vaccine in man, but new insights may enable us to exploit better what BCG can do.

BCG, muramylpeptides, trained immunity (part I): linkages in the light of the COVID-19 pandemic

It has long been known that Bacillus CalmetteGurin (BCG) vaccine provides nonspecific protection against many non-mycobacterial infections, which has been discussed in the last decade through the prism of the concept of trained immunity. Within the framework of this concept, a persistent increase in resistance to various pathogens, which occurs after an infectious disease or exposure to certain microbial agents, is associated with epigenetic reprogramming of innate immune cells and their bone marrow progenitors. The COVID-19 pandemic has drawn attention of scientists and practitioners to BCG as an inducer of trained immunity. A number of epidemiological studies have suggested a negative association between the coverage of the population with BCG vaccination and the burden of SARS-CoV-2 infection. A series of independent clinical studies of the effectiveness of this vaccine in non-specific prevention of COVID-19 has been initiated in different countries. Recently, the key role of cytosolic NOD2 receptors in BCG-induced trained immunity has been proven. This actualizes the search for effective immunoactive preparations for prevention of respiratory infections in the pandemic among low molecular weight peptidoglycan fragments of the bacterial cell wall, muramylpeptides (MPs), which are known to be NOD2 agonists. The review highlights the proven and proposed linkages between BCG, MPs, NOD2 and trained immunity in the light of the COVID-19 pandemic. Analysis of the data presented indicates the prospects for preclinical and clinical studies of MPs as potential drugs for nonspecific prevention of SARS-CoV-2 infection and/or other respiratory infections in risk groups during the pandemic. First of all, attention should be paid to glucosaminylmuramyl dipeptide, approved for clinical use in Russia and a number of post-Soviet countries for the complex treatment and prevention of acute and recurrent respiratory infections.

Benefits of BCG-induced metabolic switch from oxidative phosphorylation to aerobic glycolysis in autoimmune and nervous system diseases

The most commonly used vaccine worldwide, bacillus Calmette-Guerin (BCG), appears to have the ability to restore blood sugar control in humans with early-onset but long-duration type 1 diabetes when a repeat vaccination strategy is used. This is a process that may be driven by a metabolic switch from overactive oxidative phosphorylation to accelerated aerobic glycolysis and a reset of the immune system. BCG is a live, attenuated strain of Mycobacteria bovis, a cousin of M. tuberculosis. Humans and Mycobacteria, which are found in the environment and in warm-blooded hosts, share a long coevolutionary history. In recent times, humans have had fewer exposures to these and other microorganisms that historically helped shape the immune response. By 're-introducing' an attenuated form of Mycobacteria via BCG vaccination, humans might benefit from an immunological perspective, a concept supported by a growing body of data in autoimmunity and robust data on the nonspecific immune effects of BCG related to protection from diverse infections and early mortality. New findings of immune and metabolic defects in type 1 diabetes that can be corrected with repeat BCG vaccination suggest that this therapeutic strategy may be applicable in other diseases with inadequate aerobic glycolysis, including Parkinson's disease, dementia, depression and other disorders affecting the nervous system.

Progress and Pitfalls in the Quest for Effective SARS-CoV-2 (COVID-19) Vaccines

There are currently around 200 SARS-CoV-2 candidate vaccines in preclinical and clinical trials throughout the world. The various candidates employ a range of vaccine strategies including some novel approaches. Currently, the goal is to prove that they are safe and immunogenic in humans (phase 1/2 studies) with several now advancing into phase 2 and 3 trials to demonstrate efficacy and gather comprehensive data on safety. It is highly likely that many vaccines will be shown to stimulate antibody and T cell responses in healthy individuals and have an acceptable safety profile, but the key will be to confirm that they protect against COVID-19. There is much hope that SARS-CoV-2 vaccines will be rolled out to the entire world to contain the pandemic and avert its most damaging impacts. However, in all likelihood this will initially require a targeted approach toward key vulnerable groups. Collaborative efforts are underway to ensure manufacturing can occur at the unprecedented scale and speed required to immunize billions of people. Ensuring deployment also occurs equitably across the globe will be critical. Careful evaluation and ongoing surveillance for safety will be required to address theoretical concerns regarding immune enhancement seen in previous contexts. Herein, we review the current knowledge about the immune response to this novel virus as it pertains to the design of effective and safe SARS-CoV-2 vaccines and the range of novel and established approaches to vaccine development being taken. We provide details of some of the frontrunner vaccines and discuss potential issues including adverse effects, scale-up and delivery.

Antituberculosis BCG vaccination: more reasons for varying innate and adaptive immune responses

Bacillus Calmette-Guérin (BCG) vaccination induces variable protection against pulmonary tuberculosis (TB), and a more effective TB vaccine is needed. The potential for BCG to provide protection against heterologous infections, by induction of innate immune memory, is increasingly recognized. These nonspecific responses may substantially benefit public health, but are also variable. In this issue of the JCI, Koeken and de Bree et al. report that BCG reduces circulating inflammatory markers in males but not in females, while de Bree and Mouritis et al. describe how diurnal rhythms affect the degree of BCG-induced innate memory. These studies further delineate factors that influence the magnitude of responses to BCG and may be crucial to harnessing its potential benefits.

Epidemic and pandemic viral infections: impact on tuberculosis and the lung: A consensus by the World Association for Infectious Diseases and Immunological Disorders (WAidid), Global Tuberculosis Network (GTN), and members of the European Society of Clinical Microbiology and Infectious Diseases Study Group for Mycobacterial Infections (ESGMYC)

Major epidemics, including some that qualify as pandemics, such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), HIV, influenza A (H1N1)pdm/09 and most recently COVID-19, affect the lung. Tuberculosis (TB) remains the top infectious disease killer, but apart from syndemic TB/HIV little is known regarding the interaction of viral epidemics and pandemics with TB. The aim of this consensus-based document is to describe the effects of viral infections resulting in epidemics and pandemics that affect the lung (MERS, SARS, HIV, influenza A (H1N1)pdm/09 and COVID-19) and their interactions with TB. A search of the scientific literature was performed. A writing committee of international experts including the European Centre for Disease Prevention and Control Public Health Emergency (ECDC PHE) team, the World Association for Infectious Diseases and Immunological Disorders (WAidid), the Global Tuberculosis Network (GTN), and members of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Mycobacterial Infections (ESGMYC) was established. Consensus was achieved after multiple rounds of revisions between the writing committee and a larger expert group. A Delphi process involving the core group of authors (excluding the ECDC PHE team) identified the areas requiring review/consensus, followed by a second round to refine the definitive consensus elements. The epidemiology and immunology of these viral infections and their interactions with TB are discussed with implications for diagnosis, treatment and prevention of airborne infections (infection control, viral containment and workplace safety). This consensus document represents a rapid and comprehensive summary on what is known on the topic.

Bacillus Calmette-Guérin vaccine, antimalarial, age and gender relation to COVID-19 spread and mortality

•

COVID-19 is affecting different countries all over the world with great variation in infection rate and death ratio.

•

Some reports suggested a relation between the Bacillus Calmette-Guérin (BCG) vaccine and the malaria treatment to the infection prevention.

•

Some reports related infant's lower-susceptibility to the BCG vaccine. Some other reports a higher risk in males compared to females in such a COVI-19 pandemic.

•

Some other reports claimed the possible use of chloroquine and hydroxychloroquine as prophylactic in such a pandemic.

•

The-present commentary is to discuss the possible relation between those-factors and SARS-CoV-2 infection.

COVID-19 is affecting different countries all over the world with great variation in infection rate and death ratio. Some reports suggested a relation between the Bacillus Calmette-Guérin (BCG) vaccine and the malaria treatment to the prevention of SARS-CoV-2 infection. Some reports related infant's lower susceptibility to the COVID-19. Some other reports a higher risk in males compared to females in such COVID-19 pandemic. Also, some other reports claimed the possible use of chloroquine and hydroxychloroquine as prophylactic in such a pandemic. The present commentary is to discuss the possible relation between those factors and SARS-CoV-2 infection.

The Humoral Immune Response to BCG Vaccination

Bacillus Calmette Guérin (BCG) is the only currently available vaccine against tuberculosis (TB), but it confers incomplete and variable protection against pulmonary TB in humans and bovine TB (bTB) in cattle. Insights into the immune response induced by BCG offer an underexploited opportunity to gain knowledge that may inform the design of a more efficacious vaccine, which is urgently needed to control these major global epidemics. Humoral immunity in TB and bTB has been neglected, but recent studies supporting a role for antibodies in protection against TB has driven a growing interest in determining their relevance to vaccine development. In this manuscript we review what is known about the humoral immune response to BCG vaccination and re-vaccination across species, including evidence for the induction of specific B cells and antibodies; and how these may relate to protection from TB or bTB. We discuss potential explanations for often conflicting findings and consider how factors such as BCG strain, manufacturing methodology and route of administration influence the humoral response. As novel vaccination strategies include BCG prime-boost regimens, the literature regarding off-target immunomodulatory effects of BCG vaccination on non-specific humoral immunity is also reviewed. Overall, reported outcomes to date are inconsistent, but indicate that humoral responses are heterogeneous and may play different roles in different species, populations, or individual hosts. Further study is warranted to determine whether a new TB vaccine could benefit from the targeting of humoral as well as cell-mediated immunity.

The impact of sex hormones on BCG-induced trained immunity

The anti-tuberculosis vaccine Bacillus Calmette-Guérin (BCG) is a well-known immune modulator that induces nonspecific protective effects against heterologous infections through induction of innate immune memory, also termed "trained immunity." In randomized trials in low weight newborns, BCG vaccination reduced neonatal mortality due to decreased incidence of sepsis and respiratory infections. In many studies, sex-differential nonspecific effects of vaccines have been observed, but the mechanisms behind these differential effects are unknown. We investigated whether the important sex hormones estrogen and dihydrotestosterone (DHT) influence BCG-induced trained immunity in human primary monocytes. Although addition of estradiol and DHT to BCG inhibited the production of proinflammatory cytokines after direct stimulation of human monocytes, they did not influence the induction of trained immunity by BCG. In addition, estradiol or DHT did not induce training or tolerance in monocytes themselves. We conclude that these important sex hormones are unlikely to explain the sex-differential effects after BCG vaccination. Future studies should focus on the investigation of alternative mechanisms as an explanation for sex-differential nonspecific effects of BCG vaccination.

The impact of vaccines on heterologous adaptive immunity

BACKGROUND

Vaccines induce antigen-specific memory in adaptive immune cells that enables long-lived protection against the target pathogen. In addition to this, several vaccines have beneficial effects greater than protection against their target pathogen. These non-specific effects are proposed to be the result of vaccine-induced immunomodulation. In the case of bacille Calmette-Guérin (BCG) vaccine, this involves induction of innate immune memory, termed 'trained immunity', in monocytes and natural killer cells.

OBJECTIVES

This review discusses current evidence for vaccine-induced immunomodulation of adaptive immune cells and heterologous adaptive immune responses.

CONTENT

The three vaccines that have been associated with changes in all-cause infant mortality: BCG, diphtheria-tetanus-pertussis (DTP) and measles-containing vaccines (MCV) alter T-cell and B-cell immunity. The majority of studies that investigated non-specific effects of these vaccines on the adaptive immune system report changes in numbers or proportions of adaptive immune cell populations. However, there is also evidence for effects of these vaccines on adaptive immune cell function and responses to heterologous stimuli. There is some evidence that, in addition to BCG, DTP and MCV, other vaccines (that have not been associated with changes in all-cause mortality) may alter adaptive immune responses to unrelated stimuli.

IMPLICATIONS

This review concludes that vaccines alter adaptive immune cell populations and heterologous immune responses. The non-specific effects differ between various vaccines and their effects on heterologous adaptive immune responses may also involve bystander activation, cross-reactivity and other as yet undefined mechanisms. This has major implications for future vaccine design and vaccination scheduling.

Non-specific effects of vaccines: Current evidence and potential implications

Besides protection against specific microorganisms, vaccines can induce heterologous or non-specific effects (NSE). Epidemiological data suggest that vaccination with live-attenuated vaccines such as Bacillus Calmette-Guérin (BCG), measles vaccine, and oral polio vaccine results in increased overall childhood survival, and several of these observations have been confirmed in randomized trials. Immunological mechanisms mediating NSE include heterologous lymphocyte effects and induction of innate immune memory (trained immunity). Trained immunity induces long-term functional upregulation of innate immune cells through epigenetic and metabolic reprogramming. An overview of the epidemiological evidence of non-specific effects of vaccines and the latest insights regarding the biological mechanisms behind this phenomenon is presented, and future research priorities and potential implications are discussed.

Effect of sex on vaccination outcomes: important but frequently overlooked

It is well established that vaccination does not affect males and females equally. For example, females generally mount greater antibody responses to vaccination than males, but also suffer more adverse events following vaccination, probably as a result of more robust immunity. Despite this, most researchers in the field of vaccinology do not take biological sex into account when conducting their studies. This omission is likely to lead to a loss of important information in terms of both reactogenicity and immunogenicity following vaccination as well as those suffering adverse events. It also suggests that the vaccine dose in males and females may need to be different in order to achieve the same outcome of protective immunity while minimising reactogenicity.