Measles-mumps-rubella vaccination and respiratory syncytial virus-associated hospital contact

Trained immunity-based mucosal immunotherapies for the prevention of respiratory infections

The devastating impact of respiratory infections demonstrates the critical need for novel prophylactic vaccines. In this opinion article, we advocate for bacterial immunotherapies as a complementary tool in our fight against respiratory infections. These immunotherapies can activate a wide spectrum of immunological mechanisms, with trained immunity (TI) being particularly significant. This phenomenon has led to the concept of trained immunity-based vaccines (TIbVs), which represent a novel approach in vaccinology. We discuss examples of TIbVs, including the tuberculosis vaccine Bacille Calmette-Guérin (BCG) and the polybacterial immunotherapy MV130. From our viewpoint, illustrating the mode of action and clinical evidence supports the proposal that TIbVs should be considered as next-generation vaccines to confer protection against a wide range of respiratory infections.

The immune memory of innate immune systems

Immune memory has long been considered a function specific to adaptive immune systems; however, adaptive immune memory alone has not fully explained the mechanism by which vaccines exert their protective effects against nontarget pathogens. Recently, trained immunity, in which human monocytes vaccinated with bacillus Calmette-Guérin become highly responsive to pathogens other than Mycobacterium tuberculosis, has been reported. However, a phenomenon called endotoxin tolerance is also known, in which monocyte responsiveness is attenuated after the first lipopolysaccharide stimulation. These phenomena represent an altered innate immune response after the initial exposure to the stimulus, indicating that memories are formed in the innate immune system. In this review, we discuss trained immunity and endotoxin tolerance, known as innate immune memory, and innate immune memory formation by mRNA vaccines, which have been newly used in the coronavirus disease 2019 (COVID-19) pandemic and are considered important vaccine modalities in the future.

Vaccination against measles-mumps-rubella and rates of non-targeted infectious disease hospitalisations: Nationwide register-based cohort studies in Denmark, Finland, Norway, and Sweden

OBJECTIVES

To investigate if receipt of measles-mumps-rubella (MMR) vaccine following the third dose of diphtheria-tetanus-acellular pertussis (DTaP3) is associated with reduced rates of non-targeted infectious disease hospitalisations.

METHODS

Register based cohort study following 1,397,027 children born in Denmark, Finland, Norway, and Sweden until 2 years of age. Rates of infectious disease hospitalisations with minimum one overnight stay according to time-varying vaccination status were compared using Cox proportional hazards regression analysis with age as the underlying timescale and including multiple covariates. Summary estimates were calculated using random-effects meta-analysis.

RESULTS

Compared with DTaP3 and no MMR vaccine, MMR after DTaP3 was associated with reduced rates of infectious disease hospitalisations: aHR was 0.86 (0.83-0.89) in Denmark, 0.70 (0.64-0.75) in Finland, 0.71 (0.68-0.74) in Norway, and 0.71 (0.65-0.77) in Sweden: summary estimate was 0.75 (0.65 to 0.84). A beneficial association was also seen in a negative control exposure analysis (3 vs. 2 DTaP doses): summary estimate aHR was 0.81 (0.75-0.87).

CONCLUSIONS

Having MMR as the most recent vaccine was consistently associated with reduced rates of infectious disease hospitalisation. However, bias may account for at least some of the observed association. Randomised controlled trials are warranted to inform the optimal timing of MMR for both its specific and potential non-specific effects.

Respiratory Syncytial Virus and Influenza Infections in Children in Ulaanbaatar, Mongolia, 2015-2021

BACKGROUND

Data available for RSV and influenza infections among children < 2 years in Mongolia are limited. We present data from four districts of Ulaanbaatar from April 2015 to June 2021.

METHODS

This study was nested in an enhanced surveillance project evaluating pneumococcal conjugate vaccine (PCV13) impact on the incidence of hospitalized lower respiratory tract infections (LRTIs). Our study was restricted to children aged < 2 years with arterial O2 saturation < 93% and children with radiological pneumonia. Nasopharyngeal (NP) swabs collected at admission were tested for RSV and influenza using qRT-PCR. NP swabs of all patients with radiological pneumonia and of a subset of randomly selected NP swabs were tested for S. pneumoniae (S.p.) by qPCR and for serotypes by culture and DNA microarray.

RESULTS

Among 5705 patients, 2113 (37.0%) and 386 (6.8%) had RSV and influenza infections, respectively. Children aged 2-6 months had a higher percentage of very severe RSV infection compared to those older than 6 months (42.2% versus 31.4%, p-value Fisher's exact = 0.001). S.p. carriage was detected in 1073/2281 (47.0%) patients. Among S.p. carriage cases, 363/1073 (33.8%) had S.p. and RSV codetection, and 82/1073 (7.6%) had S.p. and influenza codetection. S.p. codetection with RSV/influenza was not associated with more severe LRTIs, compared to only RSV/influenza cases.

CONCLUSION

In Mongolia, RSV is an important pathogen causing more severe LRTI in children under 6 months of age. Codetection of RSV or influenza virus and S.p. was not associated with increased severity.

Is vaccination against measles, mumps, and rubella associated with reduced rates of antibiotic treatments among children below the age of 2 years? Nationwide register-based study from Denmark, Finland, Norway, and Sweden

OBJECTIVES

Previous studies have shown that vaccination against measles, mumps, and rubella (MMR) may have beneficial non-specific effects, reducing the risk of infections not targeted by the vaccine. We investigated if MMR vaccine given after the third dose of diphtheria-tetanus-acellular pertussis vaccine (DTaP3), was associated with reduced rates of antibiotic treatments.

METHODS

Register-based cohort study following children from the age of recommended MMR vaccination until age 2 years. We included 831,287 children born in Denmark, Finland, Norway, and Sweden who had received DTaP3 but not yet MMR vaccine. Cox proportional hazards regression with age as the underlying timescale and vaccination status as a time-varying exposure was used to estimate covariate-adjusted Hazard Ratios (aHRs) and inverse probability of treatment weighted (IPTW) HRs of antibiotic treatments. Summary estimates were calculated using random-effects meta-analysis.

RESULTS

Compared with only having received DTaP3, receipt of MMR vaccine after DTaP3 was associated with reduced rates of antibiotic treatments in all countries: the aHR was 0.92 (0.91-0.93) in Denmark, 0.92 (0.90-0.94) in Finland, 0.84 (0.82-0.85) in Norway, and 0.87 (0.85-0.90) in Sweden, yielding a summary estimate of 0.89 (0.85-0.93). A stronger beneficial association was seen in a negative control exposure analysis comparing children vaccinated with DTaP3 vs two doses of DTaP.

CONCLUSIONS

Across the Nordic countries, receipt of MMR vaccine after DTaP3 was associated with an 11% lower rate of antibiotic treatments. The negative control analysis suggests that the findings are affected by residual confounding. Findings suggest that potential non-specific effects of MMR vaccine are of limited clinical and public health importance for the milder infections treated out-of-hospital in the Nordic setting.

“The Good, the Bad and the Ugly”: Interplay of Innate Immunity and Inflammation

Innate immunity recognizes microorganisms through certain invariant receptors named pattern recognition receptors (PRRs) by sensing conserved pathogen-associated molecular patterns (PAMPs). Their recognition activates several signaling pathways that lead the transcription of inflammatory mediators, contributing to trigger a very rapid inflammatory cascade aiming to contain the local infection as well as activating and instructing the adaptive immunity in a specific and synchronized immune response according to the microorganism. Inflammation is a coordinated process involving the secretion of cytokines and chemokines by macrophages and neutrophils leading to the migration of other leukocytes along the endothelium into the injured tissue. Sustained inflammatory responses can cause deleterious effects by promoting the development of autoimmune disorders, allergies, cancer, and other immune pathologies, while weak signals could exacerbate the severity of the disease. Therefore, PRR-mediated signal transduction must be tightly regulated to maintain host immune homeostasis. Innate immunity deficiencies and strategies deployed by microbes to avoid inflammatory responses lead to an altered immune response that allows the pathogen to proliferate causing death or uncontrolled inflammation. This review analyzes the complexity of the immune response at the beginning of the disease focusing on COVID-19 disease and the importance of unraveling its mechanisms to be considered when treating diseases and designing vaccines.

Can early measles vaccination control both measles and respiratory syncytial virus infections?

Measles virus and respiratory syncytial virus (RSV) are two important global health pathogens causing substantial morbidity and mortality worldwide. The current measles vaccination schedule has the first dose given at 9–12 months of age and the second dose given at 15–18 months of age. Measles outbreaks have been associated with an increase in severe RSV infections in children younger than 6 months, probably as a result of measles-induced immunosuppression. A resurgence in measles cases was already occurring before the COVID-19 pandemic, which has affected global immunisation programmes, resulting in millions of children, mostly in low-income and middle-income countries (LMICs), missing out on their measles vaccine. This will leave many children living in the most vulnerable of circumstances highly susceptible to measles and RSV infections when current COVID-19 public health control measures are lifted. This Viewpoint discusses these issues and highlights the need for urgent action to address this looming crisis. The use of early measles vaccination at 4 months of age could be an effective strategy to prevent severe morbidity and death from both measles and RSV infections in many LMICs.

Racing to immunity: Journey to a COVID-19 vaccine and lessons for the future

SARS-CoV-2 is the novel coronavirus behind the COVID-19 pandemic. Since its emergence, the global scientific community has mobilized to study this virus, and an overwhelming effort to identify COVID-19 treatments is currently ongoing for a variety of therapeutics and prophylactics. To better understand these efforts, we compiled a list of all COVID-19 vaccines undergoing preclinical and clinical testing using the WHO and ClinicalTrials.gov database, with details surrounding trial design and location. The most advanced vaccines are discussed in more detail, with a focus on their technology, advantages and disadvantages, as well as any available recent clinical findings. We also cover some of the primary challenges, safety concerns and public responses to COVID-19 vaccine trials, and consider what this can mean for the future. By compiling this information, we aim to facilitate a more thorough understanding of the extensive COVID-19 clinical testing vaccine landscape as it unfolds, and better highlight some of the complexities and challenges being faced by the joint effort of the scientific community in finding a prophylactic against COVID-19.

Trained immunity as a novel approach against COVID-19 with a focus on Bacillus Calmette-Guérin vaccine: mechanisms, challenges and perspectives

COVID-19 is a severe health problem in many countries and has altered day-to-day life in the whole world. This infection is caused by the SARS-CoV-2 virus, and depending on age, sex and health status of the patient, it can present with variety of clinical symptoms such as mild infection, a very severe form or even asymptomatic course of the disease. Similarly to other viruses, innate immune response plays a vital role in protection against COVID-19. However, dysregulation of innate immunity could have a significant influence on the severity of the disease. Despite various efforts, there is no effective vaccine against the disease so far. Recent data have demonstrated that the Bacillus Calmette-Guérin (BCG) vaccine could reduce disease severity and the burden of several infectious diseases in addition to targeting its primary focus tuberculosis. There is growing evidence for the concept of beneficial non-specific boosting of immune responses by BCG or other microbial compounds termed trained immunity, which may protect against COVID-19. In this manuscript, we review data on how the development of innate immune memory due to microbial compounds specifically BCG can result in protection against SARS-CoV-2 infection. We also discuss possible mechanisms, challenges and perspectives of using innate immunity as an approach to reduce COVID-19 severity.

Measles-mumps-rubella vaccine at 6 months of age, immunology, and childhood morbidity in a high-income setting: study protocol for a randomized controlled trial

BACKGROUND

Measles is a highly contagious and serious infection. Before the introduction of vaccination, measles caused yearly epidemics putting vulnerable children at risk of brain damage and death. Despite safe and cost-effective vaccines, measles remains a leading cause of death in children globally. Due to insufficient vaccine coverage and low levels of in utero transferred antibodies from vaccinated mothers, outbreaks of measles in Denmark and other high-income countries are observed at increasing frequency. The current vaccine was introduced in Denmark in 1987 as a one-shot measles-mumps-rubella vaccine at 15 months, a timing chosen to avoid inhibition of the infant's immune response by maternal antibodies. One generation later, the MMR vaccinated mothers have lower antibody levels compared to the naturally infected, and their infants are already susceptible at 6 months of age or earlier, thus increasing the risk of epidemics.

METHODS

The Danish MMR trial is a double-blind randomized clinical trial recruiting between March 2019 and December 2021 with last patient last visit in February 2022. Altogether N = 6500 infants aged 6 months will be randomly assigned to intramuscular vaccination with routine MMR (M-M-R VaxPro) or placebo (solvent only). According to the Danish Childhood vaccination program, all infants will receive a routine MMR vaccination at 15 months of age. At randomization, 1 month later, and 1 month after routine MMR vaccination at 15 months of age, a blood sample is drawn from app. 10% (N = 600) of the population. Additionally, hair, saliva, and urine are sampled at randomization. The co-primary study outcomes are immunogenicity 1 month after MMR vaccination at 6 months of age assessed as plaque-reduction neutralization test, and incidence of infectious disease hospitalizations from randomization to 12 months of age. Six weeks post randomization, all participants are interviewed regarding adverse events.

TRIAL REGISTRATION

The trial is registered in the EU Clinical Trials Registry. EudraCT registration number: 2016-001901-18 . Registered on 14 February 2017.

Reduction in Short-term Outpatient Consultations After a Campaign With Measles Vaccine in Children Aged 9-59 Months: Substudy Within a Cluster-Randomized Trial

BACKGROUND

We assessed a measles vaccination campaign's potential short-term adverse events.

METHODS

In a cluster-randomized trial assessing a measles vaccination campaign's effect on all-cause mortality and hospital admission among children aged 9-59 months in Guinea-Bissau, children received a measles vaccination (intervention) or a health check-up (control). One month to 2 months later, we visited a subgroup of children to ask mothers/guardians about outpatient consultations since enrollment. In log-binomial models, we estimated the relative risk (RR) of nonaccidental outpatient consultations.

RESULTS

Among 8319 children (4437 intervention/3882 control), 652 nonaccidental outpatient consultations occurred (322 intervention/330 control). The measles vaccination campaign tended to reduce nonaccidental outpatient consultations by 16% (RR, 0.84 [95% confidence interval {CI}, .65-1.11]), especially if caused by respiratory symptoms (RR, 0.68 [95% CI, .42-1.11]). The reduction tended to be larger in children who prior to trial enrollment had a pentavalent vaccination (diphtheria, tetanus, pertussis, hepatitis B, and Haemophilus influenzae type b) as the most recent vaccination (RR, 0.61 [95% CI, .42-.89]) than in children who prior to trial enrollment had a routine measles vaccination as the most recent vaccination (RR, 0.93 [95% CI, .68-1.26]) (P = .04 for interaction).

CONCLUSIONS

In the short term, a measles vaccination campaign seems not to increase nonaccidental outpatient consultations but may reduce them.

CLINICAL TRIALS REGISTRATION

NCT03460002.

Vaccinology: time to change the paradigm?

The existing vaccine paradigm assumes that vaccines only protect against the target infection, that effective vaccines reduce mortality corresponding to the target infection's share of total mortality, and that the effects of vaccines are similar for males and females. However, epidemiological vaccine research has generated observations that contradict these assumptions and suggest that vaccines have important non-specific effects on overall health in populations. These include the observations that several live vaccines reduce the incidence of all-cause mortality in vaccinated compared with unvaccinated populations far more than can be explained by protection against the target infections, and that several non-live vaccines are associated with increased all-cause mortality in females. In this Personal View we describe current observations and contradictions and define six emerging principles that might explain them. First, that live vaccines enhance resistance towards unrelated infections. Second, non-live vaccines enhance the susceptibility of girls to unrelated infections. Third, the most recently administered vaccination has the strongest non-specific effects. Fourth, combinations of live and non-live vaccines given together have variable non-specific health effects. Fifth, vaccinating children with live vaccines in the presence of maternal immunity enhances beneficial non-specific effects and reduces mortality. Finally, vaccines might interact with other co-administered health interventions, for example vitamin A supplementation. The potential implications for child health are substantial. For example, if BCG vaccination was given to children at birth, if higher measles vaccination coverage could be obtained, if diphtheria, tetanus, and pertussis-containing vaccines were not given with or after measles vaccine, or if the BCG strain with the best non-specific effects could be used consistently, then child mortality could be considerably lower. Pursuing these emerging principles could improve our understanding and use of vaccines globally.

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.

Non-specific effects of MMR vaccines on infectious disease related hospitalizations during the second year of life in high-income countries: a systematic review and meta-analysis

Children who had received MMR as the most recent vaccine had a pooled 35% (95%CI: 12–53%) lower risk for hospitalization due to any infectious disease, compared to children who had received DTaP as the most recent vaccine (three studies, 1,919,192 children). The effect was stronger for respiratory tract infections than for gastrointestinal infections. Two studies investigated MMR alone, compared to concurrent administration of MMR and DTaP vaccines. Here, the pooled estimate for reduction in risk of hospitalization for any infectious disease was smaller and not significant (15%; 95%CI: −9% to 34%). Risk of bias was serious to critical in all studies. Moreover, two of the five studies demonstrated a significantly reduced risk for a control outcome (hospitalization for injuries), strongly indicating healthy vaccinee bias or residual confounding. The available evidence is insufficient to support a change in current vaccination schedules.

Early childhood vaccination and subsequent mortality or morbidity: are observational studies hampered by residual confounding? A Danish register-based cohort study

OBJECTIVES

To estimate the association between childhood vaccination and subsequent morbidity and mortality by adjusting for environmental and host factors. Further, to examine the degree of residual confounding in such observational studies.

DESIGN

Register-based cohort study including 1 122 929 Danish children.

PARTICIPANTS

All children born in Denmark in the period 1999-2016 who survived until 16 months of age without prior migration followed from 16 months until the first of the following: event of interest, migration, 5 years of age or 31 December 2016.

MAIN OUTCOME MEASURES

Adjusted HRs (aHRs) and absolute risks were calculated for the three outcomes: mortality, hospitalisation for infection and asthma using register data on deaths, specific hospital contacts and dispensed prescribed medication. The exposure was the combination of the routine vaccines against diphteria-tetanus-pertussis-polio-Haemophilus influenzae type b and measles-mumps-rubella (DTP and MMR in short) administered in early childhood. Hospitalisation due to accidents was analysed as a negative control outcome to examine residual confounding.

RESULTS

Children with 3DTP+MMR had a lower hazard of mortality than the reference group with 3DTP, adjusted HR (aHR)=0.45 (95% CI: 0.35 to 0.57), whereas the children with 1 or 2 DTP had higher hazards of dying, aHR=1.55 (95% CI: 1.14 to 2.13) and aHR=1.96 (95% CI: 1.34 to 2.89). The vaccination group 3DTP+MMR was associated with a reduced hazard of asthma aHR=0.94 (95% CI: 0.92 to 0.96). Also, the vaccination group 3DTP+MMR was associated with a reduced hazard of hospitalisation due to accidents, aHR=0.83 (0.80 to 0.85) compared with the reference group with 3 DTP.

CONCLUSIONS

The results suggested a beneficial impact of MMR on under-five mortality but did not support the hypothesis that DTP is detrimental, since the group of children with fewer DTP vaccinations experienced increased mortality. The results of the study may to some degree be prone to residual confounding since an unexpected association between MMR vaccination and hospitalisation for accidents was observed.

Vaccinations and Infections Are Associated With Unrelated Antibody Titers: An Analysis From the German Birth Cohort Study LISA

The evidence for non-specific effects (NSE) of vaccinations on all-cause morbidity and mortality among children is growing. However, our understanding of the underlying mechanisms is still limited. One hypothesis is that NSE are mediated by antibody titers. We used data of 2,123 children from the population-based birth cohort study LISA conducted in Germany to explore whether routine childhood vaccinations and the individual infection history in the first 2 years of life are associated with unrelated antibody titers. We selected 19 exposures (infections and vaccinations) and investigated their association with levels of 12 IgG antibody titers at the age of 2 years. Based on univariable analyses (ANOVA), we identified 21 crude associations between exposures and titers (p < 0.05), while 11 (95%-CI: 6, 17) spurious associations were expected due to multiple testing. In exploratory multivariable analyses, we observed associations between seven investigated IgG titers and 10 exposures; either administered vaccines [e.g., higher anti-hRSV IgG titer in BCG-vaccinated children (regression-coefficient in standard-deviation-units: 0.38; 95%-CI: 0.12, 0.65)] or infections [e.g., higher anti-measles IgG titer in children with reported chickenpox (0.44; 95%-CI: 0.08, 0.80)]. Our results indicate the existence of associations between immunogenic exposures and unrelated antibody titers. Further studies investigating the underlying immunological mechanisms are required.

Randomized Trial of 2 Versus 1 Dose of Measles Vaccine: Effect on Hospital Admission of Children After 9 Months of Age

BACKGROUND

Two doses of measles vaccine (MV) might reduce the nonmeasles mortality rate more than 1 dose of MV does. The effect of 2 versus 1 dose on morbidity has not been examined. Within a randomized trial of the effect of 2 doses versus 1 dose of MV on mortality in Guinea-Bissau, we investigated the effect on hospital admissions.

METHODS

Children were randomly assigned 1:2 to receive MV at 4.5 and 9 months of age or the currently recommended dose at 9 months. We compared hospital admission rates among children between 9 and 18 months of age in a Cox regression model with age as the underlying time scale. Half of the children had received neonatal vitamin A supplementation (NVAS) in another trial. The beneficial effect of MV at 4.5 and 9 months on mortality was limited to children who had not received NVAS; therefore, we investigated the interaction of MV with NVAS on admission rates.

RESULTS

Among 5626 children (2 doses of MV, 1960 children; 1 dose of MV, 3666), we identified 311 hospital admissions of children between 9 and 18 months of age. Overall, compared to 1 dose of MV, 2 doses reduced the risk of hospital admission for children who had not received NVAS (hazard ratio [HR], 0.66 [95% confidence interval (CI), 0.47-0.93]), but we found no effect among NVAS recipients (HR, 1.16 [95% CI, 0.82-1.63]) (P = .02 for interaction).

CONCLUSIONS

The benefit of 2 doses of MV was limited to children who had not received NVAS. NVAS is not generally recommended; hence, an early 2-dose measles vaccination policy might reduce hospital admissions more than the current policy of providing the first MV at 9 months of age.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT00168558.

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.

Effect of an Early Dose of Measles Vaccine on Morbidity Between 18 Weeks and 9 Months of Age: A Randomized, Controlled Trial in Guinea-Bissau

Background

Children in Guinea-Bissau receive measles vaccine (MV) at 9 months of age, but studies have shown that an additional dose before 9 months of age might have beneficial nonspecific effects. Within a randomized trial designed to examine nonspecific effects of early MV receipt on mortality, we conducted a substudy to investigate the effect of early MV receipt on morbidity.

Methods

Children were randomly assigned at a ratio of 2:1 to receive 2 doses of MV at 18 weeks and age 9 months (intervention group) or 1 dose of MV at age 9 months, in accordance with current practice (control group). Children were visited weekly from enrollment to age 9 months; the mother reported morbidity, and the field assistants examined the children. Using Cox and binomial regression models, we compared the 2 randomization groups.

Results

Among the 1592 children, early measles vaccination was not associated with a higher risk of the well-known adverse events of fever, rash, and convulsions within the first 14 days. From 15 days after randomization to age 9 months, early measles vaccination was associated with reductions in maternally reported diarrhea (hazard ratio [HR], 0.89; 95% confidence interval [CI], .82-.97), vomiting (HR, 0.86; 95% CI, .75-.98), and fever (HR, 0.93; 95% CI, .87-1.00).

Conclusion

Early MV receipt was associated with reduced general morbidity in the following months, supporting that early MV receipt may improve the general health of children.

Adaptive Characteristics of Innate Immune Responses in Macrophages

The innate immune system is considered to have no immune memory. However, lately there has been as shift in paradigm. Cells of the innate immune system, and especially monocytes and macrophages, are capable of building a nonspecific memory, resulting in either better or worse responses to secondary stimulations/infections, as a result of epigenetic changes. This review gives a general overview of the at-the-moment available data.

Effect of early measles vaccine on pneumococcal colonization: A randomized trial from Guinea-Bissau

BACKGROUND

Measles vaccine (MV) may have non-specific beneficial effects for child health and particularly seems to prevent respiratory infections. Streptococcus pneumoniae is the leading cause of bacterial pneumonia among children worldwide, and nasopharyngeal colonization precedes infection.

OBJECTIVE

We investigated whether providing early MV at 18 weeks of age reduced pneumococcal colonization and/or density up to 9 months of age.

METHOD

The study was conducted in 2013-2014 in Guinea-Bissau. Pneumococcal vaccine was not part of the vaccination program. Infants aged 18 weeks were block-randomized 2:1 to early or no early MV; at age 9 months, all children were offered MV as per current policy. Nasopharyngeal swabs were taken at baseline, age 6.5 months, and age 9 months. Pneumococcal density was determined by q-PCR. Prevalence ratios of pneumococcal colonization and recent antibiotic treatment (yes/no) by age 6.5 months (PR6.5) and age 9 months (PR9) were estimated using Poisson regression with robust variance estimates while the pneumococcal geometric mean ratio (GMR6.5 and GMR9) was obtained using OLS regression.

RESULTS

Analyses included 512 children; 346 early MV-children and 166 controls. At enrolment, the pneumococcal colonization prevalence was 80% (411/512). Comparing early MV-children with controls, the PR6.5 was 1.02 (95%CI = 0.94-1.10), and the PR9 was 1.04 (0.96-1.12). The GMR6.5 was 1.02 (0.55-1.89), and the GMR9 was 0.69 (0.39-1.21). Early MV-children tended to be less frequently treated with antibiotics prior to follow up (PR6.5 0.60 (0.34-1.05) and PR9 0.87 (0.50-1.53)). Antibiotic treatment was associated with considerably lower colonization rates, PR6.5 0.85 (0.71-1.01) and PR9 0.66 (0.52-0.84), as well as lower pneumococcal density, GMR6.5 0.32 (0.12-0.86) and GMR9 0.52 (0.18-1.52).

CONCLUSION

Early MV at age 18 weeks had no measurable effect on pneumococcal colonization prevalence or density. Higher consumption of antibiotics among controls may have blurred an effect of early MV.

TRIAL REGISTRATION

clinicaltrials.gov NCT01486355.

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.

Non-specific immunological effects of selected routine childhood immunisations: systematic review

OBJECTIVE

 To identify and characterise non-specific immunological effects after routine childhood vaccines against BCG, measles, diphtheria, pertussis, and tetanus.

DESIGN

 Systematic review of randomised controlled trials, cohort studies, and case-control studies.

DATA SOURCES

 Embase, PubMed, Cochrane library, and Trip searched between 1947 and January 2014. Publications submitted by a panel of experts in the specialty were also included.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

 All human studies reporting non-specific immunological effects after vaccination with standard childhood immunisations. Studies using recombinant vaccines, no vaccine at all, or reporting only vaccine specific outcomes were excluded. The primary aim was to systematically identify, assemble, and review all available studies and data on the possible non-specific or heterologous immunological effects of BCG; measles; mumps, measles, and rubella (MMR); diphtheria; tetanus; and pertussis vaccines.

RESULTS

 The initial search yielded 11 168 references; 77 manuscripts met the inclusion criteria for data analysis. In most included studies (48%) BCG was the vaccine intervention. The final time point of outcome measurement was primarily performed (70%) between one and 12 months after vaccination. There was a high risk of bias in the included studies, with no single study rated low risk across all assessment criteria. A total of 143 different immunological variables were reported, which, in conjunction with differences in measurement units and summary statistics, created a high number of combinations thus precluding any meta-analysis. Studies that compared BCG vaccinated with unvaccinated groups showed a trend towards increased IFN-γ production in vitro in the vaccinated groups. Increases were also observed for IFN-γ measured after BCG vaccination in response to in vitro stimulation with microbial antigens from Candida albicans, tetanus toxoid, Staphylococcus aureas, lipopolysaccharide, and hepatitis B. Cohort studies of measles vaccination showed an increase in lymphoproliferation to microbial antigens from tetanus toxoid and C albicans Increases in immunogenicity to heterologous antigens were noted after diphtheria-tetanus (herpes simplex virus and polio antibody titres) and diphtheria-tetanus-pertussis (pneumococcus serotype 14 and polio neutralising responses) vaccination.

CONCLUSIONS

 The papers reporting non-specific immunological effects had heterogeneous study designs and could not be conventionally meta-analysed, providing a low level of evidence quality. Some studies, such as BCG vaccine studies examining in vitro IFN-γ responses and measles vaccine studies examining lymphoproliferation to microbial antigen stimulation, showed a consistent direction of effect suggestive of non-specific immunological effects. The quality of the evidence, however, does not provide confidence in the nature, magnitude, or timing of non-specific immunological effects after vaccination with BCG, diphtheria, pertussis, tetanus, or measles containing vaccines nor the clinical importance of the findings.

Oral Polio Vaccination and Hospital Admissions With Non-Polio Infections in Denmark: Nationwide Retrospective Cohort Study

In a nationwide Danish register-based cohort study, the live oral polio vaccine was associated with fewer admissions for lower respiratory infections compared with the inactivated DTaP-IPV-Hib vaccine. There was no difference between oral polio vaccine and measles-mumps-rubella vaccine.

Background. Live vaccines may have nonspecific beneficial effects on morbidity and mortality. This study examines whether children who had the live-attenuated oral polio vaccine (OPV) as the most recent vaccine had a different rate of admissions for infectious diseases than children with inactivated diphtheria-tetanus-pertussis-polio-Haemophilus influenzae type b vaccine (DTaP-IPV-Hib) or live measles-mumps-rubella vaccine (MMR) as their most recent vaccine.

Methods. A nationwide, register-based, retrospective cohort study of 137 403 Danish children born 1997–1999, who had received 3 doses of DTaP-IPV-Hib, were observed from 24 months (first OPV dose) to 36 months of age.

Results. Oral polio vaccine was associated with a lower rate of admissions with any type of non-polio infection compared with DTaP-IPV-Hib as most recent vaccine (adjusted incidence rate ratio [IRR], 0.85; 95% confidence interval [CI], .77–.95). The association was separately significant for admissions with lower respiratory infections (adjusted IRR, 0.73; 95% CI, .61–.87). The admission rates did not differ for OPV versus MMR.

Conclusions. Like MMR, OPV was associated with fewer admissions for lower respiratory infections than having DTaP-IPV-Hib as the most recent vaccination. Because OPV is now being phased-out globally, further studies of the potential beneficial nonspecific effects of OPV are warranted.