Heterologous ("nonspecific") and sex-differential effects of vaccines: epidemiology, clinical trials, and emerging immunologic mechanisms

Determinants of health as predictors for differential antibody responses following SARS-CoV-2 primary and booster vaccination in an at-risk, longitudinal cohort

Post vaccine immunity following COVID-19 mRNA vaccination may be driven by extrinsic, or controllable and intrinsic, or inherent health factors. Thus, we investigated the effects of extrinsic and intrinsic on the peak antibody response following COVID-19 primary vaccination and on the trajectory of peak antibody magnitude and durability over time. Participants in a longitudinal cohort attended visits every 3 months for up to 2 years following enrollment. At baseline, participants provided information on their demographics, recreational behaviors, and comorbid health conditions which guided our model selection process. Blood samples were collected for serum processing and spike antibody testing at each visit. Cross-sectional and longitudinal models (linear-mixed effects models) were generated to assess the relationship between selected intrinsic and extrinsic health factors on peak antibody following vaccination and to determine the influence of these predictors on antibody over time. Following cross-sectional analysis, we observed higher peak antibody titers after primary vaccination in females, those who reported recreational drug use, younger age, and prior COVID-19 history. Following booster vaccination, females and Hispanics had higher peak titers after the 3rd and 4th doses, respectively. Longitudinal models demonstrated that Moderna mRNA-1273 recipients, females, and those previously vaccinated had increased peak titers over time. Moreover, drug users and half-dose Moderna mRNA-1273 recipients had higher peak antibody titers over time following the first booster, while no predictive factors significantly affected post-second booster antibody responses. Overall, both intrinsic and extrinsic health factors play a significant role in shaping humoral immunogenicity after initial vaccination and the first booster. The absence of predictive factors for second booster immunogenicity suggests a more robust and consistent immune response after the second booster vaccine administration.

Nonspecific Effects of the Bacillus Calmette-Guérin Vaccine in Portuguese Children Under 5 Years of Age: Protocol for a Population-Based Historical Birth Cohort Study

BACKGROUND

The Bacillus Calmette-Guérin vaccine (BCG) against tuberculosis (TB) shows beneficial nonspecific effects, which are likely related to innate immune training. Until 2016, a single BCG dose was administered to all newborns in Portugal. In July 2016, a clinical guideline established that only children under 6 years belonging to high-risk groups should receive BCG. This might have prevented nonvaccinated children from developing trained immunological responses as effectively as BCG-vaccinated children.

OBJECTIVE

This study aims to investigate if there is variation in TB-related and all-cause mortality, and severe, moderate, or mild morbidity in children under 5 years of age, and whether such variation might be explained by the BCG vaccination policy change in 2016.

METHODS

This population-based historical birth cohort study includes children under 5 years of age born in Portugal between July 1, 2010, and June 30, 2021. Newborns with low birth weight, premature status, or known or suspected HIV infection are excluded. The follow-up period is until the completion of 5 years of age or the end of follow-up (June 30, 2021). The study will use secondary data from the National Health Service user registry, death certificate database, vaccination registry, communicable diseases surveillance system, TB surveillance system, diagnosis-related group information system for hospital admissions and emergency department visits, and primary health care information system. The data will be linked. Primary outcomes include person-time incidence rates of death (all causes and TB), TB diagnosis, and all causes and some specific causes of severe, moderate, or mild morbidity, and the incidence rate ratio of nonvaccinated to BCG-vaccinated children. We will compare the probability of surviving the first and fifth years of life or of not having severe, moderate, or mild morbidity during the follow-up period according to exposure (BCG vaccinated or nonvaccinated, number of doses, and time from birth until the first dose), using the log-rank test for assessing differences in survival rates between exposed and nonexposed children and hazard ratios for quantifying the differences. Moreover, we will perform a proportional hazards regression analysis.

RESULTS

Ethics approval has been obtained. In March 2022, database owners were contacted to present the project and discuss the request for data. A unique identifier will be used. In July 2023, a process of redefinition of the variables per database was initiated. Data were received in October and November 2023. In November 2023, further work was conducted. By April 2024, we expect to start analyzing the full data set.

CONCLUSIONS

The results will contribute to the accumulating body of knowledge and might have relevance to guide global BCG vaccination policy. Data linkage can contribute to a swifter mechanism to use available health data to conduct population-based studies and inform policy decision-making.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05471167; https://clinicaltrials.gov/study/NCT05471167.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/55332.

Pleiotropic Effects of Influenza Vaccination

Influenza vaccines are designed to mimic natural influenza virus exposure and stimulate a long-lasting immune response to future infections. The evolving nature of the influenza virus makes vaccination an important and efficacious strategy to reduce healthcare-related complications of influenza. Several lines of evidence indicate that influenza vaccination may induce nonspecific effects, also referred to as heterologous or pleiotropic effects, that go beyond protection against infection. Different explanations are proposed, including the upregulation and downregulation of cytokines and epigenetic reprogramming in monocytes and natural killer cells, imprinting an immunological memory in the innate immune system, a phenomenon termed "trained immunity". Also, cross-reactivity between related stimuli and bystander activation, which entails activation of B and T lymphocytes without specific recognition of antigens, may play a role. In this review, we will discuss the possible nonspecific effects of influenza vaccination in cardiovascular disease, type 1 diabetes, cancer, and Alzheimer's disease, future research questions, and potential implications. A discussion of the potential effects on infections by other pathogens is beyond the scope of this review.

BCG-Induced Immune Training: Interplay between Trained Immunity and Emergency Granulopoiesis

Bacille Calmette-Guérin (BCG) is the most commonly administered vaccine in human history. The medical application of BCG extends far beyond the fight against tuberculosis. Despite its stellar medical record over 100 years, insight into how BCG provides this vast range of benefits is largely limited, both for its pathogen-specific (tuberculosis) as well as pathogen-agnostic (other infections, autoimmunity, allergies, and cancer) effects. Trained immunity and emergency granulopoiesis have been identified as mediating BCG's pathogen-agnostic effects, for which some of the molecular mechanisms have been delineated. Upon review of the existing evidence, we postulate that emergency granulopoiesis and trained immunity are a continuum of the same effect cascade. In this context, we highlight that BCG's pathogen-agnostic benefits could be optimized by taking advantage of the age of the recipient and route of BCG administration.

Trained immunity is induced in humans after immunization with an adenoviral vector COVID-19 vaccine

BackgroundHeterologous effects of vaccines are mediated by "trained immunity," whereby myeloid cells are metabolically and epigenetically reprogrammed, resulting in heightened responses to subsequent insults. Adenovirus vaccine vector has been reported to induce trained immunity in mice. Therefore, we sought to determine whether the ChAdOx1 nCoV-19 vaccine (AZD1222), which uses an adenoviral vector, could induce trained immunity in vivo in humans.MethodsTen healthy volunteers donated blood on the day before receiving the ChAdOx1 nCoV-19 vaccine and on days 14, 56, and 83 after vaccination. Monocytes were purified from PBMCs, cell phenotype was determined by flow cytometry, expression of metabolic enzymes was quantified by RT-qPCR, and production of cytokines and chemokines in response to stimulation ex vivo was analyzed by multiplex ELISA.ResultsMonocyte frequency and count were increased in peripheral blood up to 3 months after vaccination compared with their own prevaccine controls. Expression of HLA-DR, CD40, and CD80 was enhanced on monocytes for up to 3 months following vaccination. Moreover, monocytes had increased expression of glycolysis-associated enzymes 2 months after vaccination. Upon stimulation ex vivo with unrelated antigens, monocytes produced increased IL-1β, IL-6, IL-10, CXCL1, and MIP-1α and decreased TNF, compared with prevaccine controls. Resting monocytes produced more IFN-γ, IL-18, and MCP-1 up to 3 months after vaccination compared with prevaccine controls.ConclusionThese data provide evidence for the induction of trained immunity following a single dose of the ChAdOx1 nCoV-19 vaccine.FundingThis work was funded by the Health Research Board (EIA-2019-010) and Science Foundation Ireland Strategic Partnership Programme (proposal ID 20/SPP/3685).

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.

The impact of circadian rhythm on Bacillus Calmette-Guérin vaccination effects on SARS-CoV-2 infections

Background and objective

A recent study has suggested that circadian rhythm has an important impact on the immunological effects induced by Bacillus Calmette-Guérin (BCG) vaccination. The objective of this study was to evaluate whether the timing of BCG vaccination (morning or afternoon) affects its impact on severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infections and clinically relevant respiratory tract infections (RTIs).

Methods

This is a post-hoc analysis of the BCG-CORONA-ELDERLY (NCT04417335) multicenter, placebo-controlled trial, in which participants aged 60 years and older were randomly assigned to vaccination with BCG or placebo, and followed for 12 months. The primary endpoint was the cumulative incidence of SARS-CoV-2 infection. To assess the impact of circadian rhythm on the BCG effects, participants were divided into four groups: vaccinated with either BCG or placebo in the morning (between 9:00h and 11:30h) or in the afternoon (between 14:30h and 18:00h).

Results

The subdistribution hazard ratio of SARS-CoV-2 infection in the first six months after vaccination was 2.394 (95% confidence interval [CI], 0.856-6.696) for the morning BCG group and 0.284 (95% CI, 0.055-1.480) for the afternoon BCG group. When comparing those two groups, the interaction hazard ratio was 8.966 (95% CI, 1.366-58.836). In the period from six months until 12 months after vaccination cumulative incidences of SARS-CoV-2 infection were comparable, as well as cumulative incidences of clinically relevant RTI in both periods.

Conclusion

Vaccination with BCG in the afternoon offered better protection against SARS-CoV-2 infections than BCG vaccination in the morning in the first six months after vaccination.

Sex-differential non-specific effects of adjuvanted and non-adjuvanted rabies vaccines versus placebo on all-cause mortality in dogs (NERVE-Dog study): a study protocol for a randomized controlled trial with a nested case-control study

BACKGROUND

It has been proposed that childhood vaccines in high-mortality populations may have substantial impacts on mortality rates that are not explained by the prevention of targeted diseases, nor conversely by typical expected adverse reactions to the vaccines, and that these non-specific effects (NSEs) are generally more pronounced in females. The existence of these effects, and any implications for the development of vaccines and the design of vaccination programs to enhance safety, remain controversial. One area of controversy is the reported association of non-live vaccines with increased female mortality. In a previous randomized controlled trial (RCT), we observed that non-live alum-adjuvanted animal rabies vaccine (ARV) was associated with increased female but not male mortality in young, free-roaming dogs. Conversely, non-live non-adjuvanted human rabies vaccine (NRV) has been associated with beneficial non-specific effects in children. Alum adjuvant has been shown to suppress Th1 responses to pathogens, leading us to hypothesize that alum-adjuvanted rabies vaccine in young dogs has a detrimental effect on female survival by modulating the immune response to infectious and/or parasitic diseases. In this paper, we present the protocol of a 3-arm RCT comparing the effect of alum-adjuvanted rabies vaccine, non-adjuvanted rabies vaccine and placebo on all-cause mortality in an owned, free-roaming dog population, with causal mediation analysis of the RCT and a nested case-control study to test this hypothesis.

METHODS

Randomised controlled trial with a nested case-control study.

DISCUSSION

We expect that, among the placebo group, males will have higher mortality caused by higher pathogen loads and more severe disease, as determined by haematological parameters and inflammatory biomarkers. Among females, we expect that there will be no difference in mortality between the NRV and placebo groups, but that the ARV group will have higher mortality, again mediated by higher pathogen loads and more severe disease. We anticipate that these changes are preceded by shifts in key serum cytokine concentrations towards an anti-inflammatory immune response in females. If confirmed, these results will provide a rational basis for mitigation of detrimental NSEs of non-live vaccines in high-mortality populations.

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.

A Precision Adjuvant Approach to Enhance Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Vaccines Optimized for Immunologically Distinct Vulnerable Populations

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused significant mortality, especially among older adults whose distinct immune system reflects immunosenescence. Multiple SARS-CoV-2 vaccines have received emergency use authorization and/or licensure from the US Food and Drug Administration and throughout the world. However, their deployment has heighted significant limitations, such by age-dependent immunogenicity, requirements for multiple vaccine doses, refrigeration infrastructure that is not universally available, as well as waning immunity. Thus, there was, and continues to be a need for continued innovation during the pandemic given the desire for dose-sparing, formulations stable at more readily achievable temperatures, need for robust immunogenicity in vulnerable populations, and development of safe and effective pediatric vaccines. In this context, optimal SARS-CoV-2 vaccines may ultimately rely on inclusion of adjuvants as they can potentially enhance protection of vulnerable populations and provide dose-sparing effects enabling single shot protection.

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.

An integrative genomics approach identifies KDM4 as a modulator of trained immunity

Innate immune cells are able to build memory characteristics via a process termed “trained immunity.” Host factors that influence the magnitude of the individual trained immunity response remain largely unknown. Using an integrative genomics approach, our study aimed to prioritize and understand the role of specific genes in trained immunity responses. In vitro‐induced trained immunity responses were assessed in two independent population‐based cohorts of healthy individuals, the 300 Bacillus Calmette‐Guérin (300BCG; n = 267) and 200 Functional Genomics (200FG; n = 110) cohorts from the Human Functional Genomics Project. Genetic loci that influence cytokine responses upon trained immunity were identified by conducting a meta‐analysis of QTLs identified in the 300BCG and 200FG cohorts. From the identified QTL loci, we functionally validated the role of PI3K‐Akt signaling pathway and two genes that belong to the family of Siglec receptors (Siglec‐5 and Siglec‐14). Furthermore, we identified the H3K9 histone demethylases of the KDM4 family as major regulators of trained immunity responses. These data pinpoint an important role of metabolic and epigenetic processes in the regulation of trained immunity responses, and these findings may open new avenues for vaccine design and therapeutic interventions.

Non-specific effects of veterinary vaccines: a systematic review

The benefits of vaccines have been centred on their specific effects on subsequent infections by target pathogens. Recent studies, however, have opened up new insights into additional effects of vaccines known as non-specific effects (NSEs) or heterologous effects of vaccines. While several articles have reviewed epidemiological and immunological evidence for NSEs of vaccines in humans, similar works on veterinary vaccines are scarce. The objective of this paper was to review the findings of published studies on NSEs of vaccines developed or repurposed for use in animals. In total 8412 titles were retrieved from PubMed and CABI databases on the 30^th of April 2021. After the final stage of screening, 45 eligible articles were included in the review. Data from these articles were summarised and presented here. In general, most of the vaccines studied in the reviewed articles have beneficial NSEs against multiple pathogens and disease conditions. There were, however, fewe studies reporting detrimental NSEs from both non-live and live vaccines which is in contrast to the currently existing evidence of beneficial NSEs of live vaccines and detrimental NSEs of non-live vaccines. This review may be used as a complement for future review of RCT studies of NSEs of vaccines in animals and provide a useful addition to the evolving understanding of the NSEs of vaccines.

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.

Sex-differential non-specific effects of rabies vaccine in dogs: An extended analysis of a randomized controlled trial in a high-mortality population

Non-live rabies vaccines have been associated with both beneficial and detrimental effects on host population morbidity and mortality rates to unrelated infections in people and animals, and these non-specific effects may differ by sex. Previous animal studies may have been affected by bias, including selection bias due to loss to follow up in randomized controlled trials (RCTs). We previously reported results of an RCT in dogs on the effect of primary rabies vaccine administered at 6 weeks of age on all-cause mortality over a 7-week follow-up period, in a high-mortality population of owned dogs. Here, we report the results from the same trial of a second vaccination at 13 weeks of age, compared to a primary vaccination. Because a relatively high proportion of study subjects (30%) were lost to follow-up in the RCT, we also conducted an analysis to control for possible selection bias over both periods (6 to 13 weeks and 13 to 20 weeks of age). We found that primary rabies vaccination at 6 weeks of age substantially increased the hazard of death from all causes over the next 7 weeks among females (hazard ratio [HR] 2.69, 95% confidence intervals [CI] 1.27-5.69), but not among males (HR 0.91, 95% CI 0.32-2.59). Among survivors, administration of a second dose of rabies vaccine at 13 weeks of age was associated with a decreased hazard of death among males (HR 0.33, 95% CI 0.10-1.02) but not females (HR 1.64, 95% CI 0.59-4.58), when compared to the group receiving their first dose at this age. Based on our causal assumptions, we show that these results were not affected by selection bias. In this high-mortality dog population, receipt of a non-live rabies vaccine substantially affected all-cause mortality rates, with this effect being strongly modified by sex.

Interacting, Nonspecific, Immunological Effects of Bacille Calmette-Guérin and Tetanus-diphtheria-pertussis Inactivated Polio Vaccinations: An Explorative, Randomized Trial

BACKGROUND

Certain vaccines, such as Bacille Calmette-Guérin (BCG), have nonspecific effects, which modulate innate immune responses and lead to protection against mortality from unrelated infections (trained immunity). In contrast, in spite of the disease-specific effects, an enhanced overall mortality has been described after diphtheria-tetanus-pertussis (DTP) vaccination in females. This randomized trial aimed to investigate the nonspecific immunological effects of BCG and DTP-containing vaccines on the immune response to unrelated pathogens.

METHODS

We randomized 75 healthy, female, adult volunteers to receive either BCG, followed by a booster dose of tetanus-diphtheria-pertussis inactivated polio vaccine (Tdap) 3 months later; BCG and Tdap combined; or Tdap followed by BCG 3 months later. Blood was collected before vaccination, as well as at 1 day, 4 days, 2 weeks, and 3 months after the first vaccination(s), plus 2 weeks after the second vaccination. Ex vivo leukocyte responses to unrelated stimuli and pathogens were assessed.

RESULTS

Tdap vaccination led to short-term potentiation and long-term repression of monocyte-derived cytokine responses, and short-term as well as long-term repression of T-cell reactivity to unrelated pathogens. BCG led to short-term and long-term potentiation of monocyte-derived cytokine responses. When given together with Tdap or after Tdap, BCG abrogated the immunosuppressive effects of Tdap vaccination.

CONCLUSIONS

Tdap induces immunotolerance to unrelated antigens, which is partially restored by concurrent or subsequent BCG vaccination. These data indicate that the modulation of heterologous immune responses is induced by vaccination with Tdap and BCG, and more studies are warranted to investigate whether this is involved in the nonspecific effects of vaccines on mortality.

CLINICAL TRIALS REGISTRATION

NCT02771782.

COVID-19 in children: Could pertussis vaccine play the protective role?

While COVID-19 continues to spread across the globe, diligent efforts are made to understand its attributes and dynamics to help develop treatment and prevention measures. The paradox pertaining to children being the least affected by severe illness poses exciting opportunities to investigate potential protective factors. In this paper, we propose that childhood vaccination against pertussis (whooping cough) might play a non-specific protective role against COVID-19 through heterologous adaptive responses in this young population. Pertussis is a vaccine-preventable infectious disease of the respiratory tract and it shares many similarities with COVID-19 including transmission and clinical features. Although pertussis is caused by a bacterium (Bordetella pertussis) while COVID-19 is a viral infection (SARS-CoV-2), previous data showed that cross-reactivity and heterologous adaptive responses can be seen with unrelated agents of highly divergent groups, such as between bacteria and viruses. While we build the arguments of this hypothesis on theoretical and previous empirical evidence, we also outline suggested lines of research from different fields to test its credibility. Besides, we highlight some concerns that may arise when attempting to consider such an approach as a potential public health preventive intervention against COVID-19.

Timeliness of DTaP-IPV-Hib Vaccination and Development of Atopic Dermatitis Between 4 Months and 1 Year of Age-Register-Based Cohort Study

BACKGROUND

An Australian study including 4433 children found that delayed Diphtheria-Tetanus-acellular Pertussis-containing vaccination was associated with reduced risk of developing atopic dermatitis (AD) before age 1 year.

OBJECTIVE

We assessed whether delayed vaccination against diphtheria, tetanus, acellular pertussis, polio, and Haemophilus influenzae type b (Diphtheria, Tetanus, acellular Pertussis - Inactivated Polio vaccine - Haemophilus influenzae type b [DTaP]) was associated with a reduced risk of new cases of AD before age 1 year in Denmark.

METHODS

We used nationwide registers to follow 883,160 children born in Denmark from 1997 to 2012. Binary regression models adjusting for potential confounding factors were applied to estimate relative risks (adjusted relative risks [aRRs]) of developing AD among children with delayed DTaP vaccination (defined as given 1 month or more after the recommended age) compared with timely vaccinated children.

RESULTS

Among 143,429 children with a delayed first dose of DTaP, 4,847 (3.4%) developed AD between age 4 months and 1 year, compared with 27,628 (3.7%) among 739,731 children not having delayed DTaP (aRR 0.94; 95% CI, 0.91-0.97). The aRR was 0.94 (95% CI, 0.90-0.99) for children with a delayed second dose, and the aRR was 0.88 (95% CI, 0.82-0.93) when comparing children with delayed first and second doses with all timely vaccinated children.

CONCLUSIONS

The results support the hypothesis that delayed vaccination with DTaP is associated with reduced risk of developing new cases of AD after age 4 months. The dose-dependent relationship strengthens the evidence of a causal relationship. Some countries are introducing maternal pertussis vaccination and delaying the first dose of DTaP, providing a possibility for further testing the hypothesis.

Non-specific effects of rabies vaccine on the incidence of common infectious disease episodes: study protocol for a randomized controlled trial

Background

Vaccines may cause non-specific effects (NSEs) on morbidity and mortality through immune-mediated mechanisms that are not explained by the prevention of the targeted disease. Much of the evidence for NSEs comes from observational studies with a high risk of bias, and there is a clear need for new data from randomized controlled trials. Recently, it was proposed that rabies vaccine has protective NSEs in people and in animals. The aim of the proposed study is to determine whether rabies vaccine reduces the incidence rate of episodes of common infectious disease syndromes in a population of veterinary students on the island of St. Kitts.

Methods

The trial design is a single-site, two-arm, parallel-group, participant-blinded, randomized, placebo-controlled, two-sided comparative study, with an internal pilot study for blinded sample size re-estimation. Allocation to study arm is by block randomization stratified by sex within cohort with a 1:1 allocation ratio. The primary study outcome is the number of new weekly episodes of common infectious diseases including respiratory, diarrheal and febrile illnesses. A vaccine immunogenicity ancillary study is planned.

Discussion

Demonstration of a non-specific protective effect of rabies vaccine against unrelated respiratory, gastrointestinal and febrile illnesses would provide supportive evidence for the design of similar studies in children in populations with a high burden of these illnesses.

Trial registration

ClinicalTrials.gov, ID: NCT03656198. Registered on 24 August 2018.

The Tat Protein of HIV-1 Prevents the Loss of HSV-Specific Memory Adaptive Responses and Favors the Control of Viral Reactivation

The development of therapeutic strategies to control the reactivation of the Herpes Simplex Virus (HSV) is an unaddressed priority. In this study, we evaluated whether Tat, a HIV-1 protein displaying adjuvant functions, could improve previously established HSV-specific memory responses and prevent viral reactivation. To this aim, mice were infected with non-lethal doses of HSV-1 and, 44 days later, injected or not with Tat. Mice were then monitored to check their health status and measure memory HSV-specific cellular and humoral responses. The appearance of symptoms associated with HSV-reactivation was observed at significantly higher frequencies in the control group than in the Tat-treated mice. In addition, the control animals experienced a time-dependent decrease in HSV-specific Immunoglobulin G (IgG), while the Tat-treated mice maintained antibody titers over time. IgG levels were directly correlated with the number of HSV-specific CD8⁺ T cells, suggesting an effect of Tat on both arms of the adaptive immunity. Consistent with the maintenance of HSV-specific immune memory, Tat-treated mice showed a better control of HSV-1 re-infection. Although further studies are necessary to assess whether similar effects are observed in other models, these results indicate that Tat exerts a therapeutic effect against latent HSV-1 infection and re-infection by favoring the maintenance of adaptive immunity.

A Potential Role for Epigenetically Mediated Trained Immunity in Food Allergy

The prevalence of IgE-mediated food allergy is increasing at a rapid pace in many countries. The association of high food allergy rates with Westernized lifestyles suggests the role of gene-environment interactions, potentially underpinned by epigenetic variation, in mediating this process. Recent studies have implicated innate immune system dysfunction in the development and persistence of food allergy. These responses are characterized by increased circulating frequency of innate immune cells and heightened inflammatory responses to bacterial stimulation in food allergic patients. These signatures mirror those described in trained immunity, whereby innate immune cells retain a “memory” of earlier microbial encounters, thus influencing subsequent immune responses. Here, we propose that a robust multi-omics approach that integrates immunological, transcriptomic, and epigenomic datasets, combined with well-phenotyped and longitudinal food allergy cohorts, can inform the potential role of trained immunity in food allergy.

Order of Live and Inactivated Vaccines and Risk of Non-vaccine-targeted Infections in US Children 11-23 Months of Age

BACKGROUND

Some findings from observational studies have suggested that recent receipt of live vaccines may be associated with decreased non-vaccine-targeted infection risk and mortality. Our objective was to estimate risk of non-vaccine-targeted infections based on most recent vaccine type (live vaccines only, inactivated vaccines only or both concurrently) received in US children 11-23 months of age.

METHODS

We conducted a retrospective cohort study within the Vaccine Safety Datalink. We examined electronic health record and immunization data from children born in 2003-2013 who received 3 diphtheria-tetanus-acellular pertussis vaccines before their first birthday. We modeled vaccine type as a time-varying exposure and estimated risk of non-vaccine-targeted infections identified in emergency department and inpatient settings, adjusting for multiple confounders.

RESULTS

Among 428,608 children, 48.9% were female, 4.9% had ≥1 immunization visit with live vaccines only and 10.3% had a non-vaccine-targeted infection. In males, lower risk of non-vaccine-targeted infections was observed following last receipt of live vaccines only or live and inactivated vaccines concurrently as compared with last receipt of inactivated vaccines only [live vaccines-only adjusted hazard ratio (aHR) = 0.83, 95% confidence interval (CI): 0.72-0.94; live and inactivated vaccines concurrently aHR: 0.91, 95% CI: 0.88-0.94]. Among females, last receipt of live and inactivated vaccines concurrently was significantly associated with non-vaccine-targeted infection risk (aHR = 0.94, 95% CI: 0.91-0.97 vs. last receipt of inactivated vaccines only).

CONCLUSIONS

We observed modest associations between live vaccine receipt and non-vaccine-targeted infections. In this observational study, multiple factors, including healthcare-seeking behavior, may have influenced results.

Increase in Childhood Nontuberculous Mycobacterial Infections After Bacille Calmette-Guérin Coverage Drop: A Nationwide, Population-Based Retrospective Study, Finland, 1995-2016

Background

Epidemiological data on childhood nontuberculous mycobacterial (NTM) disease is scarce and the protective effect of bacille Calmette-Guérin (BCG) vaccination remains debated. In 2006, the BCG policy in Finland changed from universal to selective. We aimed to study the effect of the BCG coverage decrease on the incidence of childhood NTM infections in Finland.

Methods

We conducted a nationwide, population-based, retrospective study of NTM notifications recorded to the National Infectious Diseases Register between 1995 and 2016 and identified native-born children aged 0-4 years infected with NTM. Poisson log-linear model was used to estimate the change in the incidence rate of cohorts born during universal or selective BCG policy between 1995 and 2015.

Results

We identified 97 native-born children aged <5 years infected with NTM (median age, 27 months; female-to-male ratio, 2:1). The most common species was Mycobacterium avium (n = 69 [71%]). The estimated incidence rates of NTM in universal-BCG and selective-BCG cohorts were 0.2 and 3.9 per 100000 person-years, respectively. The incidence rate ratio of selective-BCG cohorts compared to universal-BCG cohorts was 19.03 (95% confidence interval, 8.82-41.07; P < .001).

Conclusions

After infant BCG coverage in Finland decreased, childhood NTM infections increased drastically. As there is no other apparent cause for the increase, this indicates that BCG offers protection against childhood NTM disease. This observation adds to the understanding of childhood NTM epidemiology and might explain why the disease is emerging in some countries.

Opposite effects of Vaccinia and modified Vaccinia Ankara on trained immunity

Vaccines such as Vaccinia or BCG have non-specific effects conferring protection against other diseases than their target infection, which are likely partly mediated through induction of innate immune memory (trained immunity). MVA85A, a recombinant strain of modified Vaccinia Ankara (MVA), has been suggested as an alternative vaccine against tuberculosis, but its capacity to induce positive or negative non-specific immune effects has not been studied. This study assesses whether Vaccinia and MVA are able to induce trained innate immunity in monocytes. Human primary monocytes were primed in an in vitro model with Vaccinia or MVA for 1 day, after which the stimulus was washed off and the cells were rechallenged with unrelated microbial ligands after 1 week. Heterologous cytokine responses were assessed and the capacity of MVA to induce epigenetic changes at the level of cytokine genes was investigated using chromatin immunoprecipitation and pharmacological inhibitors. Monocytes trained with Vaccinia showed significantly increased IL-6 and TNF-α production to stimulation with non-related stimuli, compared to non-trained monocytes. In contrast, monocytes primed with MVA showed significant decreased heterologous IL-6 and TNF-α responses, an effect which was abrogated by the addition of a histone methyltransferase inhibitor. No effects on H3K4me3 were observed after priming with MVA. It can be thus concluded that Vaccinia induces trained immunity in vitro, whereas MVA induces innate immune tolerance. This suggests the induction of trained immunity as an immunological mechanism involved in the non-specific effects of Vaccinia vaccination and points to a possible explanation for the lack of effect of MVA85A against tuberculosis.

Nonspecific effects of oral vaccination with live-attenuated Salmonella Typhi strain Ty21a

Epidemiological and immunological evidence suggests that some vaccines can reduce all-cause mortality through nonspecific changes made to innate immune cells. Here, we present the first data to describe the nonspecific immunological impact of oral vaccination with live-attenuated Salmonella Typhi strain Ty21a. We vaccinated healthy adults with Ty21a and assessed aspects of innate and adaptive immunity over the course of 6 months. Changes to monocyte phenotype/function were observed for at least 3 months. Changes to innate and adaptive immune cell cytokine production in response to stimulation with vaccine and unrelated nonvaccine antigens were observed over the 6-month study period. The changes that we have observed could influence susceptibility to infection through altered immune responses mounted to subsequently encountered pathogens. These changes could influence all-cause mortality.

Malaria vaccines in the eradication era: current status and future perspectives

INTRODUCTION

The challenge to eradicate malaria is an enormous task that will not be achieved by current control measures, thus an efficacious and long-lasting malaria vaccine is required. The licensing of RTS, S/AS01 is a step forward in providing some protection, but a malaria vaccine that protects across multiple transmission seasons is still needed. To achieve this, inducing beneficial immune responses while minimising deleterious non-targeted effects will be essential.

AREAS COVERED

This article discusses the current challenges and advances in malaria vaccine development and reviews recent human clinical trials for each stage of infection. Pubmed and ScienceDirect were searched, focusing on cell mediated immunity and how T cell subsets might be targeted in future vaccines using novel adjuvants and emerging vaccine technologies.

EXPERT COMMENTARY

Despite decades of research there is no highly effective licensed malaria vaccine. However, there is cause for optimism as new adjuvants and vaccine systems emerge, and our understanding of correlates of protection increases, especially regarding cellular immunity. The new field of heterologous (non-specific) effects of vaccines also highlights the broader consequences of immunization. Importantly, the WHO led Malaria Vaccine Technology Roadmap illustrates that there is a political will among the global health community to make it happen.

Association of Previous Measles Infection With Markers of Acute Infectious Disease Among 9- to 59-Month-Old Children in the Democratic Republic of the Congo

BACKGROUND

Transient immunosuppression and increased susceptibility to other infections after measles infection is well known, but recent studies have suggested the occurrence of an "immune amnesia" that could have long-term immunosuppressive effects.

METHODS

We examined the association between past measles infection and acute episodes of fever, cough, and diarrhea among 2350 children aged 9 to 59 months whose mothers were selected for interview in the 2013-2014 Democratic Republic of the Congo (DRC) Demographic and Health Survey (DHS). Classification of children who had had measles was completed using maternal recall and measles immunoglobulin G serostatus obtained via dried-blood-spot analysis with a multiplex immunoassay. The association with time since measles infection and fever, cough, and diarrhea outcomes was also examined.

RESULTS

The odds of fever in the previous 2 weeks were 1.80 (95% confidence interval [CI], 1.25-2.60) among children for whom measles was reported compared to children with no history of measles. Measles vaccination demonstrated a protective association against selected clinical markers of acute infectious diseases.

CONCLUSION

Our results suggest that measles might have a long-term effect on selected clinical markers of acute infectious diseases among children aged 9 to 59 months in the DRC. These findings support the immune-amnesia hypothesis suggested by others and underscore the need for continued evaluation and improvement of the DRC's measles vaccination program.

First International Precision Vaccines Conference: Multidisciplinary Approaches to Next-Generation Vaccines

Vaccines represent a remarkable success in the history of medicine since they have prevented and, in some instances, eradicated a range of infectious diseases. However, for many existing vaccines, immunogenicity is limited, requiring multiple booster doses, and we are still unable to target many pathogens due to intrinsic features of the microorganism, such as genetic/antigenic variability between strains, and our limited understanding of the variables that regulate vaccine responsiveness, including age- and sex-specific differences. Moreover, the traditional approach to vaccine development is often empirical, relying on inactivation of microorganisms or purification of their components, which are usually less immunogenic than the whole microorganism from which they derive. This approach has yielded multiple important vaccines but has failed to consistently generate vaccines that are sufficiently immunogenic in populations with limited immune responsiveness such as newborns and elderly individuals. In an effort to trigger impactful collaborations, a community of scientists gathered in Boston in the United States for the first biennial International Precision Vaccines Conference, sponsored by the Boston Children's Hospital Precision Vaccines Program, to discuss innovation in vaccinology. Recent advancements in the field of systems biology that can identify vaccine immunogenicity biomarkers for target populations, in human in vitro models, and in novel adjuvant and formulation strategies offer unprecedented opportunities to dissect the human immune response to vaccines and inform dramatic improvements in vaccine efficacy. These approaches are poised to have a major scientific and translational impact in vaccinology.

Sex and Gender Differences in the Outcomes of Vaccination over the Life Course

Both sex (i.e., biological differences) and gender (i.e., social or cultural influences) impact vaccine acceptance, responses, and outcomes. Clinical data illustrate that among children, young adults, and aged individuals, males and females differ in vaccine-induced immune responses, adverse events, and protection. Although males are more likely to receive vaccines, following vaccination, females typically develop higher antibody responses and report more adverse effects of vaccination than do males. Human, nonhuman animal, and in vitro studies reveal numerous immunological, genetic, hormonal, and environmental factors that differ between males and females and contribute to sex- and gender-specific vaccine responses and outcomes. Herein, we address the impact of sex and gender variables that should be considered in preclinical and clinical studies of vaccines.

The Case for an Expanded Concept of Trained Immunity

Trained immunity was originally proposed as a program of innate immunity memory by innate immunity cells of hematopoietic origin such as the monocytes/macrophages and the NK cells. Here I discuss some old and new data justifying this program and some specific, still unanswered, questions it raises regarding the model fungus Candida albicans and the chronic, inflammatory vulvovaginal disease it causes. Building upon this well-established program, the recent reports that epithelial cells of mammals can also acquire memory from previous stimulations, and the apparent intrinsic ability of many living cells from bacteria to mammals to learn from experience, I suggest an expansion of the concept of trained immunity to include all cells of different lineages with the potential of memorizing previous microbial encounters. This expansion would better fit the complexity of innate immunity and the role it plays in infectious and inflammatory diseases.

Paramunity-inducing Factors (PINDs) in dendritic cell (DC) cultures lead to impaired antileukemic functionality of DC-stimulated T-cells

INTRODUCTION

Paramunity-inducing-Factors (PINDs) consist of attenuated/inactivated viruses of various poxvirus-genera, used in veterinary medicine as non-antigen-specific, non-immunising stimulators of the innate immune system against infectious and malignant diseases. Their danger-signaling-interactions were tested for their capacity to improve leukemic antigen-presentation on DC generated from AML-patients' blasts ('DC_leu') and DC-stimulation/activation of antileukemic T-cells.

METHODS

We analyzed, whether the addition of PINDs during DC cultures (15 healthy, 22 leukemic donors) and mixed lymphocyte culture (MLC, n = 15) with autologous (n = 6), allogeneic (n = 2) or T-cells after stem cell transplantation (SCT; n = 7) would alter the quality and quantity of DC, the composition of T-cell-subsets, and/or their antileukemic functionality (AF) as studied by FACS and functional Fluorolysis-cytotoxicity-assays.

RESULTS

Effects on 1. DC-cultures: PINDs in DC-cultures lead to increased proportions of mature DC and DC_leu, but reduced proportions of viable and overall, as well as TLR4- and TLR9-expressing DC. 2. MLC: PINDs increased early (CD8+) T-cell activation (CD69+), but reduced proportions of effector-T-cells after MLC 3. AF: Presence of PINDs in DC- and MLC-cultures reduced T-cells' as well as innate cells' antileukemic functionality. 4. Cytokine-release profile: Supernatants from PIND-treated DC- and MLC-cultures resembled an inhibitory microenvironment, correlating with impaired blast lysis.

CONCLUSIONS

Our data shows that addition of PINDs to DC-cultures and MLC result in a "blast-protective-capacity" leading to impaired AF, likely due to changes in the composition of T-/innate effector cells and the induction of an inhibitory microenvironment. PINDs might be promising in treating infectious diseases, but cannot be recommended for the treatment of AML-patients due to their inhibitory influence on antileukemic functionality.

Measles Vaccination Supports Millennium Development Goal 4: Increasing Coverage and Increasing Child Survival in Northern Ghana, 1996-2012

Background

Measles vaccine (MV) administered as the last vaccine after the third dose of diphtheria-tetanus-pertussis (DTP) may be associated with better child survival unrelated to prevention of measles infection. Other studies have shown that MV administered after DTP was more beneficial and was associated with lower mortality compared with DTP administered after MV or DTP administered simultaneously with MV. We compared the difference in mortality between measles vaccinated after DTP3 and measles-unvaccinated children in Navrongo, Ghana.

Methods

This was a follow-up study involving annual cohort of children aged 9–23 months from 1996 to 2012. We assessed survival in relation to the measles vaccination status within the first 12 months from interview date and until 5 years of age using Cox proportional hazards models.

Results

In all, 38,333 children were included in the study. The proportion of children vaccinated with MV-after-DTP3 increased from 45% in 1996 to 95% in 2012. The adjusted hazard ratio (HR) for measles unvaccinated compared with MV-after-DTP3 vaccinated children was 1.38 (1.15–1.66) in the first 12 months after assessment of vaccination status and 1.22 (1.05–1.41) with follow-up to 5 years of age. The national immunization days campaigns with oral polio vaccine or MV might have reduced the effect of being MV-after-DTP3 vaccinated vs MV-unvaccinated. For 12 months of follow-up, the HR before a campaign for MV-unvaccinated children was 1.63 (1.23–2.17) compared to those who received MV-after-DTP3. After the campaign, the HR reduced to 1.23 (0.97–1.54). Stratifying the analysis by sex, measles-unvaccinated boys had a HR of 1.69 (1.33–2.61) compared to measles-unvaccinated girls who had a HR 1.06 (0.79–1.40) during 1-year follow-up. In 1989, only 7% of children in the area had received MV-after-DTP3; the increase in MV-after-DTP3 coverage from 1989 to 2012 may have lowered mortality rate among children aged 9 months to 3 years by 24%.

Conclusion

Though an observational study, our findings suggest that measles vaccination, administered in the recommended sequence, is associated with improved child survival and may have contributed importantly to the mortality decline toward the achievement of Millennium Development Goal 4.

Non-specific effects of BCG vaccination on morbidity among children in Greenland: a population-based cohort study

Background

The potential non-specific effects of BCG (Bacillus Calmette-Guérin) vaccination, with reported reduction of infectious disease morbidity among vaccinated children, in addition to the protective effect against tuberculosis (TB), are highly debated. In Greenland, BCG vaccination was introduced in 1955, but temporarily discontinued from 1991 to 1996 due to nationwide policy changes. Using the transient vaccination stop, we aimed to investigate possible non-specific effects of BCG vaccination by measuring nation-wide hospitalization rates due to infectious diseases other than TB among vaccinated and unvaccinated children.

Methods

A retrospective cohort study including all children born in Greenland aged 3 months to 3 years from 1989 to 2004. A personal identification number assigned at birth allowed for follow-up through national registers. Information on hospitalization due to infectious diseases was obtained from the Greenlandic inpatient register using ICD-8 and ICD-10 codes. Participants with notified TB were censored. Incidence rate ratios (IRR) were estimated using Poisson regression.

Results

Overall, 19 363 children, hereof 66% BCG-vaccinated, were followed for 44 065 person-years and had 2069 hospitalizations due to infectious diseases. IRRs of hospitalization in BCG-vaccinated as compared with BCG-unvaccinated children were 1.07 [95% confidence interval (CI) 0.96-1.20] for infectious diseases overall, and specifically 1.10 (95% CI 0.98-1.24) for respiratory tract infections. Among BCG-vaccinated children aged 3 to 11 months, the IRR of hospitalization due to infectious diseases was 1.00 (95% CI 0.84-1.19) as compared with BCG-unvaccinated children.

Conclusion

Our results do not support the hypothesis that neonatal BCG vaccination reduces morbidity in children caused by infectious diseases other than TB.

Adjuvant Effect of Bacille Calmette-Guérin on Hepatitis B Vaccine Immunogenicity in the Preterm and Term Newborn

Immunization is key to protecting term and preterm infants from a heightened risk of infection. However, preterm immunity is distinct from that of the term, limiting its ability to effectively respond to vaccines routinely given at birth, such as hepatitis B vaccine (HBV). As part of the Expanded Program on Immunization, HBV is often given together with the live-attenuated vaccine Bacille Calmette-Guérin (BCG), known to activate multiple pattern-recognition receptors. Of note, some clinical studies suggest BCG can enhance efficacy of other vaccines in term newborns. However, little is known about whether BCG can shape Th-polarizing cytokine responses to HBV nor the age-dependency of such effects, including whether they may extend to the preterm. To characterize the effects of BCG on HBV immunogenicity, we studied individual and combined administration of these vaccines to cord newborn and adult human whole blood and mononuclear cells in vitro and to neonatal and adult mice in vivo. Compared to either BCG or HBV alone, (BCG + HBV) synergistically enhanced in vitro whole blood production of IL-1β, while (BCG + HBV) also promoted production of several cytokines/chemokines in all age groups, age-specific enhancement included IL-12p70 in the preterm and GM-CSF in the preterm and term. In human mononuclear cells, (BCG + HBV) enhanced mRNA expression of several genes including CSF2, which contributed to clustering of genes by vaccine treatment via principle component analysis. To assess the impact of BCG on HBV immunization, mice of three different age groups were immunized subcutaneously with, BCG, HBV, (BCG + HBV) into the same site; or BCG and HBV injected into separate sites. Whether injected into a separate site or at the same site, co-administration of BCG with HBV significantly enhanced anti-HBV IgG titers in mice immunized on day of life-0 or -7, respectively, but not in adult mice. In summary, our data demonstrate that innate and adaptive vaccine responses of preterm and term newborns are immunologically distinct. Furthermore, BCG or "BCG-like" adjuvants should be further studied as a promising adjuvantation approach to enhance immunogenicity of vaccines to protect these vulnerable populations.

Minimal Sex-Differential Modulation of Reactivity to Pathogens and Toll-Like Receptor Ligands following Infant Bacillus Calmette-Guérin Russia Vaccination

Bacillus Calmette–Guérin (BCG), the only licensed vaccine against tuberculosis, has been shown to provide heterologous protection against unrelated pathogens and enhance antibody responses to several routine expanded program on immunization (EPI) vaccines. Understanding these heterologous effects is important for the development of optimal vaccination strategies. We set out to assess the effect of vaccination with BCG Russia of 6-week-old infants on in vitro reactivity to a panel of toll-like receptor (TLR) agonists (TLR2, 4, and 7/8) and heat-killed pathogens [Streptococcus pneumoniae, Candida albicans (CA), and Escherichia coli], and antibody responses to other EPI vaccines compared to BCG naïve infants. We observed no effect of BCG vaccination on innate (TNF-α) or Th2 (IL-4) cytokine responses, but found enhanced CA-specific CD8⁺IFN-γ⁺ responses in BCG vaccinated males and females 1 week after vaccination and decreased IFN-γ:IL4 ratio to SP in females. By 12 weeks (but not 1 week) of post-vaccination, there was significant downmodulation of Th1 cytokine responses in BCG vaccinated infants; and TLR-stimulated IL-10 and IL-17 responses declined in BCG vaccinated females but not males. Significant changes also occurred in the BCG naïve group, mainly at 18 weeks, including decreased Th1 and increased IL-10 responses. The effects at 18 weeks were most likely a result of immune modulation by the intervening EPI vaccines given at 8, 12, and 16 weeks of age. There was no effect of BCG vaccination on EPI antibody levels at either time point. Taken together, our results support minimal early heterologous immune modulation by BCG Russia vaccination that did not persist 12 weeks after vaccination.

Non-specific effects of measles, mumps, and rubella (MMR) vaccination in high income setting: population based cohort study in the Netherlands

Objectives To investigate whether measles, mumps, and rubella (MMR) vaccine has positive non-specific effects in a high income setting and to compare rates of hospital admissions for infections between children aged ≤2 years who received live MMR vaccine and those who received an inactivated vaccine against diphtheria, tetanus, pertussis, polio, and Haemophilus influenzae type b (DTaP-IPV-Hib) as their most recent vaccination.Design Nationwide population based cohort study.Setting In the Netherlands, DTaP-IPV-Hib+pneumococcal vaccination (PCV) is recommended at ages 2, 3, 4, and 11 months and MMR + meningococcal C (MenC) vaccination at age 14 months. Data from the national vaccine register were linked to hospital admission data.Participants 1 096 594 children born in 2005-11 who received the first four DTaP-IPV-Hib+PCV vaccines.Main outcome measures Hazard ratio for admission to hospital for infection in children with MMR+MenC compared with the fourth DTaP-IPV-Hib+PCV as their most recent vaccination. Cox regression was performed with most recent vaccination as time dependent variable, adjusted for potential confounders. Analyses were repeated with admission for injuries or poisoning as a negative control outcome. In addition, rate of admission for infection was compared between the fourth and third DTaP-IPV-Hib+PCVas most recent vaccination.Results Having had MMR+MenC as the most recent vaccination was associated with a hazard ratio of 0.62 (95% confidence interval 0.57 to 0.67) for admission to hospital for infection and 0.84 (0.73 to 0.96) for injuries or poisoning, compared with the fourth DTaP-IPV-Hib+PCV as most recent vaccination. The fourth DTaP-IPV-Hib+PCV as most recent vaccination was associated with a hazard ratio of 0.69 (0.63 to 0.76) for admission to hospital for infection, compared with the third DTaP-IPV-Hib+PCV as most recent vaccination.Conclusions Healthy vaccinee bias could at least partly explain the observed lower rate of admission to hospital with infection after MMR vaccination. The lower rate is associated with receipt of any additional vaccine, not specifically MMR vaccine. This emphasises the caution required in the interpretation of findings from observational studies on non-specific effects of vaccination.

Negative Correlation between Circulating CD4+FOXP3+CD127- Regulatory T Cells and Subsequent Antibody Responses to Infant Measles Vaccine but Not Diphtheria-Tetanus-Pertussis Vaccine Implies a Regulatory Role

Regulatory T cells (Tregs) play a key homeostatic role by suppressing immune responses. They have been targeted in mouse and human cancer studies to improve vaccine immunogenicity and tumor clearance. A number of commercially available drugs and experimental vaccine adjuvants have been shown to target Tregs. Infants have high numbers of Tregs and often have poor responses to vaccination, yet the role Tregs play in controlling vaccine immunogenicity has not been explored in this age group. Herein, we explore the role of CD4⁺FOXP3⁺CD127^- Tregs in controlling immunity in infant males and females to vaccination with diphtheria-tetanus-whole cell pertussis (DTP) and/or measles vaccine (MV). We find correlative evidence that circulating Tregs at the time of vaccination suppress antibody responses to MV but not DTP; and Tregs 4 weeks after DTP vaccination may suppress vaccine-specific cellular immunity. This opens the exciting possibility that Tregs may provide a future target for improved vaccine responses in early life, including reducing the number of doses of vaccine required. Such an approach would need to be safe and the benefits outweigh the risks, thus further research in this area is required.

Mycobacterium bovis Bacillus Calmette-Guérin Alters Melanoma Microenvironment Favoring Antitumor T Cell Responses and Improving M2 Macrophage Function

Intralesional Mycobacterium bovis bacillus Calmette-Guérin (BCG) has long been a relatively inexpensive therapy for inoperable cutaneous metastatic melanoma (CMM), although intralesional BCG skin mechanisms remain understudied. We analyzed intralesional BCG-treated CMM lesions combined with in vitro studies to further investigate BCG-altered pathways. Since macrophages play a pivotal role against both cancer and mycobacterial infections, we hypothesized BCG regulates macrophages to promote antitumor immunity. Tumor-associated macrophages (M2) infiltrate melanomas and impair antitumor immunity. BCG-treated, in vitro-polarized M2 (M2-BCG) showed transcriptional changes involving inflammation, immune cell recruitment, cross talk, and activation pathways. Mechanistic network analysis indicated M2-BCG potential to improve interferon gamma (IFN-γ) responses. Accordingly, frequency of IFN-γ-producing CD4+ T cells responding to M2-BCG vs. mock-treated M2 increased (p < 0.05). Moreover, conditioned media from M2-BCG vs. M2 elevated the frequency of granzyme B-producing CD8+ tumor-infiltrating lymphocytes (TILs) facing autologous melanoma cell lines (p < 0.01). Furthermore, transcriptome analysis of intralesional BCG-injected CMM relative to uninjected lesions showed immune function prevalence, with the most enriched pathways representing T cell activation mechanisms. In vitro-infected MM-derived cell lines stimulated higher frequency of IFN-γ-producing TIL from the same melanoma (p < 0.05). Our data suggest BCG favors antitumor responses in CMM through direct/indirect effects on tumor microenvironment cell types including macrophages, T cells, and tumor itself.

Rabies vaccine is associated with decreased all-cause mortality in dogs

Evidence suggests that rabies vaccine may have non-specific protective effects in animals and children. We analyzed four years of data (2012-2015) from an observational study of the health and demographics of a population of owned, free-roaming dogs in a low-income community in South Africa. The objective of this analysis was to assess the association between rabies vaccine and all-cause mortality in dogs, stratified by age group (0-3months, 4-11months, and 12months and older), and controlling for the effects of sex and number of dogs in the residence. Rabies vaccination reduced the risk of death from any cause by 56% (95% CI=16-77%) in dogs aged 0-3months, by 44% (95% CI=21-60%) in dogs aged 4-11months and by 16% (95% CI=0-29%) in dogs aged 12months and older. We hypothesize that the protective association between rabies vaccination status and all-cause mortality is due to a protective effect of rabies vaccine against diseases other than rabies. Existence of a strong non-specific protective effect of rabies vaccine on mortality in dogs would have implications for the design of dog rabies control programs that aim to eliminate dog-mediated human rabies cases. Further, we propose that owned domestic dogs in high mortality settings provide a useful animal model to better understand any non-specific protective effect of rabies vaccine in children, due to dogs' high numbers, high morbidity and mortality rates, relatively short lifespan, exposure to a variety of infectious and parasitic diseases, and shared environment with people.

Immunological considerations regarding parental concerns on pediatric immunizations

Despite the fundamental role of vaccines in the decline of infant mortality, parents may decide to decline vaccination for their own children. Many factors may influence this decision, such as the belief that the infant immune system is weakened by vaccines, and concerns have been raised about the number of vaccines and the early age at which they are administered. Studies focused on the infant immune system and its reaction to immunizations, summarized in this review, show that vaccines can overcome those suboptimal features of infant immune system that render them more at risk of infections and of their severe manifestations. In addition, many vaccines have been shown to improve heterologous innate and adaptive immunity resulting in lower mortality rates for fully vaccinated children. Thus, multiple vaccinations are necessary and not dangerous, as infants can respond to several antigens as well as when responding to single stimuli. Current immunization schedules have been developed and tested to avoid vaccine interference, improve benefits and reduce side effects compared to single administrations. The infant immune system is therefore capable, early after birth, of managing several antigenic challenges and exploits them to prompt its development.

Is diphtheria-tetanus-pertussis (DTP) associated with increased female mortality? A meta-analysis testing the hypotheses of sex-differential non-specific effects of DTP vaccine

BACKGROUND

Ten years ago, we formulated two hypotheses about whole-cell diphtheria-tetanus-pertussis (DTP) vaccination: first, when given after BCG, DTP increases mortality in girls and, second, following DTP there is an increase in the female/male mortality rate ratio (MRR). A recent review by WHO found no convincing evidence that DTP increases mortality in females.

METHODS

We used previous DTP reviews as well as the recent WHO review for assessing the hypotheses. As pre-specified we excluded studies with survival or frailty bias; if children had received BCG and DTP simultaneously; and if the children had received neonatal vitamin A.

RESULTS

In seven studies of BCG-vaccinated children, DTP vaccination was associated with a 2.54 (95% CI 1.68-3.86) increase in mortality in girls (with no increase in boys [ratio 0.96, 0.55-1.68]). In 10 studies of BCG-vaccinated children, the female-to-male mortality ratio was 2.45 (1.48-4.06) times higher after DTP than before DTP. In 15 studies of children who had received DTP after previous BCG vaccination, mortality was 1.53 (1.21-1.93) times higher in girls than boys. The findings were similar in studies conducted before and after formulation of the hypotheses.

CONCLUSIONS

The two hypotheses were confirmed in the studies that fulfilled pre-specified criteria.

Vaccination and unexplained sudden death risk in Taiwanese infants

PURPOSE

In March 1992, eight infants who had died within 36 hours of receiving whole-cell pertussis vaccine (diphtheria, tetanus, and whole-cell pertussis [DTwP]) prompted the Taiwan health authorities to suspend its use. We conducted an investigation of vaccination and sudden unexplained infant death (SUID) and repeated it more recently after Taiwan switched to acellular pertussis vaccine (diphtheria, tetanus, and acellular pertussis [DTaP]) in 2010.

METHODS

All SUIDs aged 31-364 days during 1990-1992 and 1996-2013 were selected from the death registration databases. The case-control investigation matched each case to two controls on clinic, sex, and birth date, whereas the follow-up self-controlled case series study compared risk of death during the 30-day post-vaccination risk periods with those in the control periods within the same case.

RESULTS

Sudden unexplained infant death was associated with never receiving DTwP (odds ratio 2.28, 95% confidence interval 1.25-4.15) in the case-control investigation. The odds ratios within 0-1, 2-7, 8-14, and 15-30 days of DTwP administration were 1.18, 0.26, 0.50, and 0.77. In the 1996-2013 self-controlled case series studies, this temporal shift between DTwP and SUID was consistently observed for female (incidence rate ratio 1.70, 0.75, 1.01, and 0.84) but not male or DTaP recipients. A pooled analysis showed significant risk within 2 days of receiving DTwP in female infants (incidence rate ratio 1.66, 95% confidence interval 1.05-2.60).

CONCLUSIONS

Being unvaccinated and recent receipt of DTwP in female infants was significantly associated with SUID; the latter was consistent with a temporal shift pattern without overall increase in risk. The currently used pertussis vaccine, DTaP, did not increase risk of SUID. Copyright © 2016 John Wiley & Sons, Ltd.

Simultaneous vaccination with MMR and DTaP-IPV-Hib and rate of hospital admissions with any infections: A nationwide register based cohort study

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Nationwide retrospective cohort study of Danish children aged 15 months to 4 years.

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Comparison of the live MMR + the inactivated DTaP-IPV-Hib vaccine vs MMR alone.

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27% higher rate of admissions for lower respiratory infections for MMR + DTaP-IPV-Hib.

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No significant association with admissions for other types of infections.

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Adjustment for a long range of potential confounders including exact age.

Background

In Denmark, live measles, mumps, and rubella vaccine (MMR) is associated with a reduced risk of infectious disease admissions, particularly for lower respiratory tract infections. In low-income countries, simultaneous vaccination (i.e. vaccination at the same visit) with live and inactivated vaccines may increase child mortality compared with the live vaccine alone. We examined the hypothesis that simultaneous administration of MMR and the inactivated DTaP-IPV-Hib vaccine compared with MMR alone is associated with higher incidence of infectious disease admissions.

Methods

Nationwide, retrospective, register based cohort study of 520,859 children born in Denmark 1997–2006, who were followed from 15 months to 4 years of age. Incidence rate ratios (IRRs) of hospital admissions were estimated by Cox regression and adjusted for background factors including exact age.

Results

By 2 years of age, 4965 children had simultaneous MMR and DTaP-IPV-Hib as their most recent vaccination. Compared with MMR alone, simultaneous administration was associated with a higher rate of lower respiratory tract infections (adjusted incidence rate ratio (IRR), 1.27; 95% confidence interval (CI), 1.13–1.42). There was no effect on other infections. Overall, simultaneous administration was associated with a 7% (95% CI, 0–15%) increase in infectious disease admissions.

Conclusions

Simultaneous administration of MMR and DTaP-IPV-Hib compared with MMR alone may increase the rate of hospital admissions related to lower respiratory tract infections. These findings require replication in other high-income settings.