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

Maternal Bacille Calmette-Guérin Scars and Mortality Risk for Male and Female Newborns: Observational Study From Guinea-Bissau

BACKGROUND

Maternal priming with bacille Calmette-Guérin (BCG) has been associated with reduced mortality in male offspring. We investigated this association in a cohort of healthy BCG-vaccinated neonates.

METHODS

This observational study within a randomized controlled trial comparing different BCG strains was conducted in Guinea-Bissau from 2017 to 2020. As part of trial inclusion procedures, on the day of discharge from the maternity ward, maternal BCG scar status was evaluated by visual inspection, followed by offspring BCG and polio vaccination. Through mortality data collected at telephone interviews at 6 weeks and 6 months of age, we assessed all-cause mortality risk in Cox proportional hazards models adjusted for maternal schooling and BCG strain, providing adjusted mortality rate ratios (aMRRs).

RESULTS

In total, 64% (11 070/17 275) of mothers had a BCG scar, which was not associated with admission risk, admission severity, or all-cause mortality for females and the overall sample. By 6 months of age, the mortality rate (MR) was 4.1 (200 deaths/4919 person-years) for the maternal BCG scar cohort and 5.2 (139/2661) for no maternal scar (aMRR, 0.86; 95% Confidence Interval [CI], .69-1.06). In males, 6-month MRs were 4.3 (109 deaths/2531 person-years) for maternal BCG scar vs 6.3 (87/1376) for no scar (aMRR, 0.74; 95% CI, .56-.99). In females, 6-month MRs were 3.8 (91 deaths/2388 person-years) vs 4.0 (52/1286), respectively (aMRR, 1.04; 95% CI, .74-1.47; for interaction with sex, P = .16).

CONCLUSIONS

While we cannot rule out an association in females, being born to a mother with a BCG scar reduced the risk of death during early infancy for BCG-vaccinated males, reproducing findings from previous studies.

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.

Prenatal Maternal Immunization for Infant Protection: A Review of the Vaccines Recommended, Infant Immunity and Future Research Directions

Prenatal maternal immunization is an effective tool to protect mothers and infants from poor health outcomes due to infectious diseases. We provide an overview of the rationale for the use of prenatal vaccines, discuss the immunologic environment of the maternal-fetal interface including the impact of maternal vaccines prenatally and subsequently on the infant's immune response, and review vaccines currently recommended in pregnancy and landscape for the future of maternal vaccination. This review aims to provide an understanding of the recent history and progress made in the field and highlight the importance of continued research and development into new vaccines for pregnant populations.

Can earlier BCG-Japan and OPV vaccination reduce early infant mortality? A cluster-randomised trial in Guinea-Bissau

OBJECTIVE

To assess the effect of providing BCG and oral polio vaccine (OPV) at an early home visit after delivery.

DESIGN

Cluster-randomised trial, randomising 92 geographically defined clusters 1:1 to intervention/control arms.

SETTING

Bandim Health Project Health and Demographic Surveillance System, Guinea-Bissau.

PARTICIPANTS

2226 newborns enrolled between July 2016 and August 2019.

INTERVENTIONS

In both arms, newborns received a home visit within 72 hours after birth. In intervention clusters (n=46), BCG and OPV were provided at the home visit.

MAIN OUTCOME MEASURE

Rates of non-accidental mortality were compared in Cox proportional hazards models from (last of) day 1 or enrolment, until (first of) day 60 or registration of non-trial vaccines.

RESULTS

A total of 35 deaths (intervention: 7, control: 28) were registered during the trial. Providing BCG and OPV reduced non-accidental early infant mortality by 59% (8-82%). The intervention also reduced non-accidental hospital admissions. The intervention had little impact on growth and BCG scarring and tended to increase the risk of consultations.

CONCLUSIONS

The trial was stopped early due to lower-than-expected enrolment and event rates when 33% of the planned number of newborns had been enrolled. Despite the small size of the trial, the results support that early BCG and OPV vaccinations are beneficial and reduce early child mortality and morbidity.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT02504203).

Beneficial non-specific effects of live vaccines against COVID-19 and other unrelated infections

Live attenuated vaccines could have beneficial, non-specific effects of protecting against vaccine-unrelated infections, such as BCG protecting against respiratory infection. During the COVID-19 pandemic, testing of these effects against COVID-19 was of interest to the pandemic control programme. Non-specific effects occur due to the broad effects of specific live attenuated vaccines on the host immune system, relying on heterologous lymphocyte responses and induction of trained immunity. Knowledge of non-specific effects has been developed in randomised controlled trials and observational studies with children, but examining of whether the same principles apply to adults and older adults was of interest to researchers during the pandemic. In this Personal View, we aim to define a framework for the analysis of non-specific effects of live attenuated vaccines against vaccine-unrelated infections with pandemic potential using several important concepts. First, study endpoints should prioritise severity of infection and overall patient health rather than incidence of infection only (eg, although several trials found no protection of the BCG vaccine against COVID-19 infection, it is associated with lower overall mortality than placebo). Second, revaccination of an individual with the same live attenuated vaccine could be the most effective strategy against vaccine-unrelated infections. Third, coadministration of several live attenuated vaccines might enhance beneficial non-specific effects. Fourth, the sequence of vaccine administration matters; the live attenuated vaccine should be the last vaccine administered before exposure to the pandemic infection and non-live vaccines should not be administered afterwards. Fifth, live attenuated vaccines could modify the immune response to specific COVID-19 vaccines. Finally, non-specific effects of live attenuated vaccines should always be analysed with subgroup analysis by sex of individuals receiving the vaccines.

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.

Mortality risk among frail neonates might be associated with maternal BCG scar status: Observational study from Guinea-Bissau

BACKGROUND

Maternal priming with Bacille Calmette-Guérin (BCG) has been associated with reduced offspring mortality. We investigated this association in a cohort of frail neonates.

METHODS

We performed an observational study within a randomized BCG trial conducted at the Neonatal Intensive Care Unit (NICU) in Guinea-Bissau from 2015-2017. At NICU admission and following informed consent, the maternal scar status was evaluated by visual inspection before neonates were randomized 1:1 to receive BCG + Oral Polio Vaccine (OPV) immediately versus BCG + OPV at hospital discharge. Stratified by maternal scar status, we assessed overall in-hospital and post-discharge mortality up to 42 days of age in Cox Proportional Hazards models providing adjusted Mortality Rate Ratios (aMRRs).

RESULTS

62% (903/1451) of mothers had a BCG scar. During NICU admission, the mortality risk was 1.7% (15/903) for neonates born to mothers with a scar vs 3.3% (18/548) for those born to mothers with no scar, the maternal scar/no scar aMRR = 0.53 (0.26-1.05); the aMRR was 0.39 (0.13-1.05) for unvaccinated neonates and 0.70 (0.26-1.87) for vaccinated neonates.

CONCLUSION

This small study indicates that maternal BCG might be associated with reduced all-cause NICU mortality. If confirmed elsewhere, this finding would have substantial ramifications for global health.