The WHO Review of the Possible Nonspecific Effects of Diphtheria-Tetanus-Pertussis Vaccine

Do vaccines increase or decrease susceptibility to diseases other than those they protect against?

Contrary to the long-held belief that the effects of vaccines are specific for the disease they were created; compelling evidence has demonstrated that vaccines can exert positive or deleterious non-specific effects (NSEs). In this review, we compiled research reports from the last 40 years, which were found based on the PubMed search for the epidemiological and immunological studies on the non-specific effects (NSEs) of the most common human vaccines. Analysis of information showed that live vaccines induce positive NSEs, whereas non-live vaccines induce several negative NSEs, including increased female mortality associated with enhanced susceptibility to other infectious diseases, especially in developing countries. These negative NSEs are determined by the vaccination sequence, the antigen concentration in vaccines, the type of vaccine used (live vs. non-live), and also by repeated vaccination. We do not recommend stopping using non-live vaccines, as they have demonstrated to protect against their target disease, so the suggestion is that their detrimental NSEs can be minimized simply by changing the current vaccination sequence. High IgG4 antibody levels generated in response to repeated inoculation with mRNA COVID-19 vaccines could be associated with a higher mortality rate from unrelated diseases and infections by suppressing the immune system. Since most COVID-19 vaccinated countries are reporting high percentages of excess mortality not directly attributable to deaths from such disease, the NSEs of mRNA vaccines on overall mortality should be studied in depth.

Do Pentavalent (DTwP-Hib-HBV) vaccines have sex-differential nonspecific effects? An observational study

Vaccines may alter the ability to combat infections unrelated to the target disease, i.e. have "nonspecific effects." The non-live Diphtheria-Tetanus-Pertussis vaccine (DTP) has been associated with increased child mortality, especially for females. In 2008, the DTP-containing Pentavalent vaccine replaced DTP vaccine in Guinea-Bissau. We investigate female relative to male mortality after Penta vaccination. In Guinea-Bissau, Bandim Health Project (BHP) registered children's vaccination and vital status at biannual village visits and provided vaccines. Among children Penta-vaccinated by BHP, we compared mortality of males and females in Cox proportional hazards models. Children aged 6 weeks to 8 months entered the analysis at the date of vaccination and were followed for up to 6 months. Between September 2008 and December 2017, 33,989 children aged 6 weeks to 8 months were under surveillance. Of these 12,753 (females: 6,363; males: 6,390) received Penta by the BHP and entered the study contributing with 19,667 observations. The mortality rate following Penta vaccination was 25.2 per 1,000 person years for females and 26.6 for males, resulting in an adjusted Female/Male mortality rate ratio of (F/M aMRR) 1.01 (0.82-1.25). The association between sex and mortality differed by timeliness of vaccination, F/M aMRR: 0.62 (0.41-0.93) for children vaccinated below median age, and F/M aMRR: 1.38 (0.90-2.13) for children vaccinated above median age. We did not find higher overall mortality in females than males after Penta vaccination. Our findings suggest that mortality differences between males and females following Penta vaccination may depend on timeliness of Penta vaccination.

Measles vaccination and reduced child mortality: Prevention of immune amnesia or beneficial non-specific effects of measles vaccine?

Measles vaccine (MV) has been observed to reduce all-cause mortality more than explained by prevention of measles infection. Recently, prevention of "measles-induced immune amnesia" (MIA) has been proposed as an explanation for this larger-than-anticipated beneficial effect of measles vaccine (MV). According to the "MIA hypothesis", immune amnesia leads to excess non-measles morbidity and mortality, that may last up to five years after measles infection, but may be prevented by MV. However, the benefits of MV-vaccinated children could also be due to beneficial non-specific effects (NSEs) of MV, reducing the risk of non-measles infections (The "NSE hypothesis"). The epidemiological studies do provide some support for MIA, as exposure to measles infection before 6 months of age causes long-term MIA, and over 6 months of age for 2-3 months. However, in children over 6 months of age, the MIA hypothesis is contradicted by several epidemiological patterns: First, in community studies that adjusted for MV status, children surviving acute measles infection had lower mortality than uninfected controls (44%(95%CI: 0-69%)). Second, in six randomised trials and six observational studies comparing MV-vaccinated and MV-unvaccinated children, the benefit of MV changed minimally from 54%(43-63%) to 49%(37-59%) when measles cases were censored in the survival analysis, making it unlikely that prevention of measles and its long-term consequences explained much of the reduced mortality. Third, several studies conducted in measles-free contexts still showed significantly lower mortality after MV (55%(40-67%)). Fourth, administration of MV in the presence of maternal measles antibody (MatAb) is associated with much stronger beneficial effect for child survival than administration of MV in the absence of MatAb (55%(35-68%) lower mortality). The MIA hypothesis alone cannot explain the strongly beneficial effects of MV on child survival. Conversely, the hypothesis that MV has beneficial non-specific immune training effects is compatible with all available data. Consideration should be given to continuing MV even when measles has been eradicated.

Implications of Non-Specific Effects for Testing, Approving, and Regulating Vaccines

The current framework for testing and regulating vaccines was established before the realization that vaccines, in addition to their effect against the vaccine-specific disease, may also have "non-specific effects" affecting the risk of unrelated diseases. Accumulating evidence from epidemiological studies shows that vaccines in some situations can affect all-cause mortality and morbidity in ways that are not explained by the prevention of the vaccine-targeted disease. Live attenuated vaccines have sometimes been associated with decreases in mortality and morbidity that are greater than anticipated. In contrast, some non-live vaccines have in certain contexts been associated with increases in all-cause mortality and morbidity. The non-specific effects are often greater for female than male individuals. Immunological studies have provided several mechanisms that explain how vaccines might modulate the immune response to unrelated pathogens, such as through trained innate immunity, emergency granulopoiesis, and heterologous T-cell immunity. These insights suggest that the framework for the testing, approving, and regulating vaccines needs to be updated to accommodate non-specific effects. Currently, non-specific effects are not routinely captured in phase I-III clinical trials or in the post-licensure safety surveillance. For instance, an infection with Streptococcus pneumoniae occurring months after a diphtheria-tetanus-pertussis vaccination would not be considered an effect of the vaccination, although evidence indicates it might well be for female individuals. Here, as a starting point for discussion, we propose a new framework that considers the non-specific effects of vaccines in both phase III trials and post-licensure.

Bordetella pertussis whole cell immunization protects against Pseudomonas aeruginosa infections

Whole cell vaccines are complex mixtures of antigens, immunogens, and sometimes adjuvants that can trigger potent and protective immune responses. In some instances, such as whole cell Bordetella pertussis vaccination, the immune response to vaccination extends beyond the pathogen the vaccine was intended for and contributes to protection against other clinically significant pathogens. In this study, we describe how B. pertussis whole cell vaccination protects mice against acute pneumonia caused by Pseudomonas aeruginosa. Using ELISA and western blot, we identified that B. pertussis whole cell vaccination induces production of antibodies that bind to lab-adapted and clinical strains of P. aeruginosa, regardless of immunization route or adjuvant used. The cross-reactive antigens were identified using immunoprecipitation, mass spectrometry, and subsequent immunoblotting. We determined that B. pertussis GroEL and OmpA present in the B. pertussis whole cell vaccine led to production of antibodies against P. aeruginosa GroEL and OprF, respectively. Finally, we showed that recombinant B. pertussis OmpA was sufficient to induce protection against P. aeruginosa acute murine pneumonia. This study highlights the potential for use of B. pertussis OmpA as a vaccine antigen for prevention of P. aeruginosa infection, and the potential of broadly protective antigens for vaccine development.

Non-specific effects of BCG and DTP vaccination on infant mortality: An analysis of birth cohorts in Ghana and Tanzania

BACKGROUND

Vaccines may induce non-specific effects on survival and health outcomes, in addition to protection against targeted pathogens or disease. Observational evidence suggests that infant Baccillus Calmette-Guérin (BCG) vaccination may provide non-specific survival benefits, while diphtheria-tetanus-pertussis (DTP) vaccination may increase the risk of mortality. Non-specific vaccine effects have been hypothesized to modify the effect of neonatal vitamin A supplementation (NVAS) on mortality.

METHODS

22,955 newborns in Ghana and 31,999 newborns in Tanzania were enrolled in two parallel, randomized, double-blind, placebo-controlled trials of neonatal vitamin A supplementation from 2010 to 2014 and followed until 1-year of age. Cox proportional hazard models were used to estimate associations of BCG and DTP vaccination with infant survival.

RESULTS

BCG vaccination was associated with a decreased risk of infant mortality after controlling for confounders in both countries (Ghana adjusted hazard ratio (aHR): 0.51, 95% CI: 0.38-0.68; Tanzania aHR: 0.08, 95% CI: 0.07-0.10). Receiving a DTP vaccination was associated with a decreased risk of death (Ghana aHR: 0.39, 95% CI: 0.26-0.59; Tanzania aHR: 0.19, 95% CI: 0.16-0.22). There was no evidence of interaction between BCG or DTP vaccination status and infant sex or NVAS.

CONCLUSION

We demonstrated that BCG and DTP vaccination were associated with decreased risk of infant mortality in Ghana and Tanzania with no evidence of interaction between DTP or BCG vaccination, NVAS, and infant sex. Our study supports global recommendations on BCG and DTP vaccination and programmatic efforts to ensure all children have access to timely vaccination.

CLINICAL TRIALS REGISTRATION

Ghana (Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12610000582055) and Tanzania (ANZCTR: ACTRN12610000636055).

Immunisation with the BCG and DTPw vaccines induces different programs of trained immunity in mice

In addition to providing pathogen-specific immunity, vaccines can also confer nonspecific effects (NSEs) on mortality and morbidity unrelated to the targeted disease. Immunisation with live vaccines, such as the BCG vaccine, has generally been associated with significantly reduced all-cause infant mortality. In contrast, some inactivated vaccines, such as the diphtheria, tetanus, whole-cell pertussis (DTPw) vaccine, have been controversially associated with increased all-cause mortality especially in female infants in high-mortality settings. The NSEs associated with BCG have been attributed, in part, to the induction of trained immunity, an epigenetic and metabolic reprograming of innate immune cells, increasing their responsiveness to subsequent microbial encounters. Whether non-live vaccines such as DTPw induce trained immunity is currently poorly understood. Here, we report that immunisation of mice with DTPw induced a unique program of trained immunity in comparison to BCG immunised mice. Altered monocyte and DC cytokine responses were evident in DTPw immunised mice even months after vaccination. Furthermore, splenic cDCs from DTPw immunised mice had altered chromatin accessibility at loci involved in immunity and metabolism, suggesting that these changes were epigenetically mediated. Interestingly, changing the order in which the BCG and DTPw vaccines were co-administered to mice altered subsequent trained immune responses. Given these differences in trained immunity, we also assessed whether administration of these vaccines altered susceptibility to sepsis in two different mouse models. Immunisation with either BCG or a DTPw-containing vaccine prior to the induction of sepsis did not significantly alter survival. Further studies are now needed to more fully investigate the potential consequences of DTPw induced trained immunity in different contexts and to assess whether other non-live vaccines also induce similar changes.

Quadrivalent human papillomavirus vaccination and non-targeted infectious disease hospitalisation: Population-based self-controlled case series analysis

Background

Claims of non-live vaccines having deleterious effects on non-targeted infectious disease and mortality among females persists. The majority of the available evidence is from West Africa and consists of observational studies and the interpretation and implications are controversial. Results from high-income countries have been conflicting. We evaluated the association between a human papillomavirus vaccine, a non-live vaccine primarily administered to pre-adolescent females, and non-targeted infectious disease in a high-income country.

Methods

We constructed a nationwide cohort of all Danish females 10 to 29 years of age during 2007 to 2016 with information on quadrivalent human papillomavirus vaccination status and infectious disease hospital contacts using national registers. Nested in this cohort, we conducted a self-controlled case series (SCCS) analysis comparing the rates of hospitalisation in a 90-day main risk period following the latest vaccination to reference period rates with adjustment for age and season.

Findings

We included 853,879 Danish-born females aged 10 to 29 years of age during the 2007 to 2016 study period in the study cohort. We identified a total of 65,293 infectious disease hospitalisations among 50,599 participants; 46,955 cases among 37,003 participants vaccinated during follow-up were included in the SCCS analysis. There was no statistically significantly increased risk of infectious disease hospitalisation in the 90-day main risk period (rate ratio 0.92, 95% CI 0.88 to 0.95).

Interpretation

Reassuringly, our large well-controlled study does not support that human papillomavirus vaccination increases the risk of non-targeted infectious disease in any clinically meaningful way. While our study does not provide evidence against adverse effects of other non-live vaccines, it does provide evidence against the claim that all non-live vaccines increase risk of heterologous infections in females.

Funding

The study was supported by the Novo Nordisk Foundation.

Retesting the hypothesis that early Diphtheria-Tetanus-Pertussis vaccination increases female mortality: An observational study within a randomised trial

BACKGROUND

There are worrying indications that diphtheria-tetanus-pertussis (DTP) vaccine has negative non-specific effects for females. We previously found, in a trial of early-Bacillus Calmette-Guérin (BCG) to low weight (LW) neonates, that receiving early-DTP (before 2 months of age), was associated with increased female mortality compared with no-DTP/delayed-DTP. Within a subsequent LW trial, we aimed to retest this observation.

METHODS

Between 2010 and 2014, in Guinea-Bissau, 2,398 infants were randomised 1:1 to early-BCG (intervention) or delayed-BCG (standard practice for LW neonates) and visited at 2, 6 and 12 months of age to assess nutritional and vaccination status. DTP is recommended at 6 weeks of age. We examined the effect of having "early-DTP" versus "no-DTP" at the time of the 2-month visit on all-cause mortality between the 2- and 6-month visits in Cox models stratified by sex and adjusted for BCG-group and 2-month-weight-for-age (z-scores) providing adjusted mortality rate ratios (aMRRs). We analysed to which extent conditions varied between the present and the previous LW trials and how that might have affected the overall result of comparing the early-DTP and the no-DTP groups.

RESULTS

At the time of the 2-month visit, 75% (1,795/2,398) had received DTP. Those vaccinated had better anthropometric indices than no-DTP infants at birth and by 2 months of age. Between the 2- and 6-month visits, 29 deaths occurred. The early-DTP/no-DTP aMRR was 1.09 (95% CI: 0.44-2.69); 1.19 (0.45-3.15) for females and 0.77 (0.14-4.19) for males. Compared to the previous study, the present study cohort had 56% (30-72%) lower overall mortality, fewer no-DTP infants, higher BCG vaccination coverage and several more oral polio vaccine campaigns.

CONCLUSION

We did not find that early-DTP was associated with increased female mortality as found in a previous study; differences in results may partly be due to a decline in overall mortality and changes in vaccination practices.

Vaccine safety issues at the turn of the 21st century

Global gains in vaccination coverage during the early 21st century have been threatened by the emergence of antivaccination groups that have questioned the effectiveness of vaccines to generate public distrust of vaccines and immunisation programmes. This manuscript summarises six key topics that have been at the centre of global discussions on vaccine safety during the early 21st century: thiomersal in multi-dose non-live vaccines, aluminium adjuvants used with several non-live vaccines, autism and auto-immune conditions as possible consequences of vaccination, a risk of immune overload with increasing numbers of vaccinations, and detrimental non-specific effects (NSEs) of vaccination. For each topic, we describe the hypothesis behind the public concern, the evidence reviewed by the WHO’s Global Advisory Committee for Vaccine Safety (GACVS) during 1999–2019, and any significant new data that has emerged since GACVS conclusions were made. Although the scientific evidence on these issues overwhelmingly supports the safety of vaccines, communication messages to caregivers and providers need to condense and convey scientific information in an appropriate way to address concerns contributing to vaccine distrust. In addition, there is need for further studies specifically designed to address both positive and negative NSE of vaccination. The role of GACVS will be increasingly important in evaluating the evidence and engaging the global community in promoting and assuring the safety of vaccines in the decades to come as we move into an era in which we use new vaccination platforms, antigens and formulations.

Non-specific effects of rabies vaccine on the incidence of self-reported common infectious disease episodes: A randomized controlled trial

Vaccines may affect recipients' immune systems in ways that change morbidity or mortality rates to unrelated infections in vaccinated populations. It has been proposed that these non-specific effects differ by type of vaccine and by sex, with non-live vaccines enhancing susceptibility of females to unrelated infections, and live vaccines enhancing resistance in both sexes. Rabies vaccine-a non-live vaccine-has been associated with protection against unrelated central nervous system infections. Data from randomized controlled trials are needed to assess this effect against other illnesses. This phase IV, single-site, participant-blinded, randomized, placebo-controlled trial in a population of veterinary students on the rabies-free island of St. Kitts assessed the effect of a primary course of rabies vaccine on the incidence rate of weekly self-reported new episodes of common infectious disease (CID) syndromes, defined as a new episode of any one of the following syndromes in a particular week: upper respiratory illness (URI), influenza-like illness (ILI), diarrheal illness (DIA) or undifferentiated febrile illness (UFI). As a secondary objective, we tested for modification of the effect of rabies vaccine on study outcomes by sex. 546 participants were randomized (274 to rabies vaccine and 272 to placebo). No statistically significant differences between groups were observed for any study outcomes: CID incidence rate ratio (IRR) 0.95 (95% CI 0.77-1.18); URI IRR 1.15 (95% CI 0.86-1.54); ILI IRR 0.83 (95% CI 0.54-1.27); DIA IRR 0.93 (95% CI 0.70-1.24) and UFI IRR 1.09 (95% CI 0.48-2.44). In a secondary analysis, there was little evidence that sex modified the effect of vaccination on any of the evaluated outcomes, although the power to detect this was low. In conclusion, rabies vaccine did not provide protection against mild self-reported illness among a young and healthy group of adults attending veterinary school. Clinical trial registration. ClinicalTrials.gov: NCT03656198.

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.

Reduced Mortality After Oral Polio Vaccination and Increased Mortality After Diphtheria-tetanus-pertussis Vaccination in Children in a Low-income Setting

PURPOSE

The diphtheria-tetanus-pertussis vaccine (DTP) and oral polio vaccine (OPV) were introduced in children 3 of 5 months of age in 1981-1983 in Bandim, in the capital of Guinea-Bissau. Because DTP has been linked to deleterious nonspecific effects (NSEs) and OPV to beneficial NSEs, we followed up this cohort to 3 years of age and examined the effects of DTP with OPV on all-cause mortality and the interactions of DTP and OPV with the measles vaccine (MV).

METHODS

DTP and OPV were offered at 3 monthly community weighing sessions. Vaccination groups were defined by the last vaccine received. We compared overall mortality for different groups in Cox proportional hazards regression models, reporting hazards ratios (HRs) with 95% CIs.

FINDINGS

The study cohort included 1491 children born in Bandim from December 1980 to December 1983. From 3 to 35 months of age, with censoring for MV, children vaccinated with DTP and/or OPV had higher mortality than both unvaccinated children (HR = l.66; 95% CI, 1.03-2.69) and OPV-only vaccinated children (HR = 2.81; 95% CI, 1.02-7.69); DTP-only vaccinated children had higher mortality than OPV-only vaccinated children (HR = 3.38; 95% CI, 1.15--9.93). In the age group of 3-8 months, before MV is administered, DTP-only vaccination was associated with a higher mortality than DTP with OPV (HR = 3.38; 95% CI, 1.59-7.20). Between 9 and 35 months of age, when MV is given, DTP-vaccinated and MV-unvaccinated children had higher mortality (HR = 2.76; 95% CI, 1.36-5.59) than children who had received MV after DTP, and among children who received DTP with MV or after MV, DTP-only vaccination was associated with a higher mortality than DTP with OPV (HR = 6.25; 95% CI, 2.55-15.37).

IMPLICATIONS

Because the 2 vaccines had differential effects and the healthiest children were vaccinated first, selection biases are unlikely to explain the estimated impact on child survival. OPV had beneficial NSEs, and administration of OPV with DTP may have reduced the negative effects of DTP.

Multiple Vaccinations and the Enigma of Vaccine Injury

A growing number of vaccines are administered at the same time or in close succession, increasing the complexity of assessing vaccine safety. Individual vaccines are assumed to have no other effect than protection against the targeted pathogen, but vaccines also have nonspecific and interactive effects, the outcomes of which can be beneficial or harmful. To date, no controlled trials and very few observational studies have determined the impact of vaccination schedules on overall health. The balance of the risks and benefits from mass vaccination therefore remains uncertain. Recent studies worryingly suggest links between multiple vaccinations and increased risks of diverse multisystem health problems, including allergies, infections, and neuropsychiatric or neurodevelopmental disorders. Here, we propose that, in susceptible persons, multiple vaccinations activate the retinoid cascade and trigger apoptotic hepatitis, leading to cholestatic liver dysfunction, in which stored vitamin A compounds (retinyl esters and retinoic acid) enter the circulation in toxic concentrations; this induces endogenous forms of hypervitaminosis A, with the severity of adverse outcomes being directly proportional to the concentration of circulating retinoids. In very low concentrations, vitamin A and its major metabolite retinoic acid contribute to immune function and to the process of immunization, whereas excess vitamin A increases the risk of adverse events, including common "side-effects" as well as chronic adverse outcomes. The increasing rates of allergy, ear infections, and neurodevelopmental disorders (NDDs) in countries with high rates of vaccination could be related to mass vaccination and to its impact on liver function and vitamin A metabolism, collectively representing endogenous manifestations of hypervitaminosis A. Further studies of health outcomes in vaccinated and unvaccinated groups are urgently needed, to increase understanding of the pathophysiology and treatment of vaccine injury, to identify the risk factors and screen for vaccine injury, to inform public health policy on potential hazards related to vaccination schedules, and to optimize the safety and benefits of vaccines.

Diphtheria-Tetanus-Pertussis (DTP) Vaccine Is Associated With Increased female-Male Mortality. Studies of DTP administered before and after measles vaccine

Background

The third dose of diphtheria-tetanus-pertussis vaccine (DTP3) is used to monitor immunization programs. DTP has been associated with higher female mortality.

Methods

We updated previous literature searches for DTP studies of mortality by sex. We examined the female/male (F/M) mortality rate ratio (MRR) with increasing number of doses of DTP and for subsequent doses of measles vaccine (MV) after DTP and of DTP after MV.

Results

Eight studies had information on both DTP1 and DTP3. The F/M MRR was 1.17 (95% confidence interval [CI], .88–1.57) after DTP1 and increased to 1.66 (95% CI, 1.32–2.09) after DTP3. Following receipt of MV, the F/M MRR declined to 0.63 (95% CI, .42–.96). In 11 studies the F/M MRR increased to 1.73 (95% CI, 1.33–2.27) when DTP-containing vaccine was administered after MV.

Conclusions

F/M MRR increased with increasing doses of DTP. After MV, girls had lower mortality than boys. With DTP after MV, mortality increased again for girls relative to boys. No bias can explain these changes in F/M MRR. DTP does not improve male survival substantially in situations with herd immunity to pertussis and higher F/M MRR after DTP may therefore reflects an absolute increase in female mortality.

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.

Penta is associated with an increased female-male mortality ratio: cohort study from Bangladesh

Diphtheria-tetanus-pertussis (DTP) vaccine may be associated with excess female deaths. There are few studies of possible nonspecific effects of the DTP-containing vaccine Penta (DTP-hepatitis B-Haemophilus influenzae type b). We therefore investigated whether Penta vaccinations were associated with excess female deaths in rural Bangladesh. Between June 29, 2011 and April 20, 2016, we examined the mortality rates of 7644 children followed between 6 weeks and 9 months of age. We analyzed mortality using crude mortality rate ratio (MRR) and age-adjusted MRR (aMRR) from a Cox proportional hazards model. Mortality was analyzed according to sex, number of doses of Penta, and the order in which BCG and Penta were administered. During follow-up, 43 children died. For children who were only BCG vaccinated (BCG-only), the adjusted F/M MRR was 0.47 (0.09-2.48). However, among children who had Penta as their most recent vaccination, the adjusted F/M MRR was 9.91 (1.16-84.44). Hence, the adjusted F/M MRR differed significantly for BCG-only and for Penta as the most recent administered vaccination. Although the mortality rate was low in rural Bangladesh, there was a marked difference between adjusted F/M MRR's for children vaccinated with BCG-only compared with children where Penta was the most recent administered vaccination. Although usually ascribed to differential treatment and access to care, DTP-containing vaccines may be part of the explanation for the excessive female mortality reported in some regions.

The non-specific and sex-differential effects of vaccines

The textbook view of vaccination is that it functions to induce immune memory of the specific pathogen components of the vaccine, leading to a quantitatively and qualitatively better response if the host is exposed to infection with the same pathogen. However, evidence accumulated over the past few decades increasingly suggests that vaccines can also have non-specific effects on unrelated infections and diseases, with important implications for childhood mortality particularly in low-income settings. Furthermore, many of these non-specific effects, as well as the pathogen-specific effects, of vaccines show differences between the sexes. Here, members of the Optimmunize consortium discuss the evidence for and potential mechanisms of non-specific and sex-differential effects of vaccines, as well as their potential policy implications. Given that the non-specific effects of some vaccines are now being tested for their ability to protect against COVID-19, the authors also comment on the broader implications of these trials.

In this Viewpoint article, members of the Optimmunize consortium discuss the evidence for non-specific and sex-differential effects of vaccines and how this information might inform vaccine design and policy, including in relation to the COVID-19 pandemic.

Peter Aaby was trained as an anthropologist but has built a large health surveillance system in Guinea-Bissau since 1978, focusing on the high levels of child mortality there. Crowding and intensive exposure to measles were key determinants of child mortality. This led to vaccine research and the discovery of the non-specific effects of measles vaccine.

Christine Stabell Benn is a professor in global health at the University of Southern Denmark. She conducts epidemiological and immunological studies of vaccines and vitamin A, with a focus on their real-life effects on overall health in Africa and Denmark. She formulated the hypothesis that these health interventions with immunomodulatory effects interact, often in a sex-differential manner.

Katie L. Flanagan is Director of Infectious Diseases for north/north-west Tasmania, an adjunct professor at the University of Tasmania and RMIT University and an adjunct associate professor at Monash University. She is Honorary Secretary of the Australasian Society for Infectious Diseases (ASID), Chair of the ASID Vaccination Special Interest Group and a member of the Australian Technical Advisory Group on Immunisation. Her current research focuses on using systems vaccinology to study the sex-differential and non-targeted effects of vaccines.

Sabra L. Klein is a professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health, Baltimore, USA. She is an expert on sex and gender differences in immune responses and susceptibility to infection. She is the immediate past president of the Organization for the Study of Sex Differences, a principal investigator of the Johns Hopkins Specialized Center for Research Excellence in sex and age differences in immunity to influenza and a co-director of the Johns Hopkins Center for Women’s Health, Sex, and Gender Research.

Tobias R. Kollmann is a paediatric infectious disease clinician and systems vaccinologist at Telethon Kids Institute and Perth Children’s Hospital in Perth, Australia. His expertise centres on newborn infectious diseases, immune ontogeny and early-life vaccine responses, using cutting-edge technology and analytics to extract the most information out of the typically small biological samples obtainable in early life.

David J. Lynn is Director of the Computational and Systems Biology Program and an EMBL Australia group leader at the South Australian Health and Medical Research Institute. He is also a professor at the Flinders University College of Medicine and Public Health. He leads a research programme in systems immunology, investigating how pathogenic and commensal microorganisms modulate the immune system in different contexts, including vaccination.

Frank Shann worked as a paediatrician in Papua New Guinea and then for 20 years was Director of Intensive Care at the Royal Children’s Hospital in Melbourne, Australia. He is a professorial fellow in the Department of Paediatrics, University of Melbourne, engaged in research on the non-specific effects of vaccines.

Study protocol for the Melbourne Infant Study: BCG for Allergy and Infection Reduction (MIS BAIR), a randomised controlled trial to determine the non-specific effects of neonatal BCG vaccination in a low-mortality setting

INTRODUCTION

BCG vaccination reduces all-cause infant mortality in high-mortality settings by more than can be attributed to protection against tuberculosis. This is proposed to result from non-specific protection against non-vaccine targeted ('off-target') infections. There is also evidence that BCG protects against allergic diseases.

METHODS AND ANALYSIS

The Melbourne Infant Study: BCG for Allergy and Infection Reduction is a phase III multicentre, single-blinded, randomised controlled trial. A total of 1438 healthy neonates will be randomised to receive either BCG vaccination or no BCG vaccination in the first 10 days of life. Measures of allergy, eczema, infection and asthma will be obtained from parent-completed questionnaires 3 monthly in the first year and 6 monthly from 1 to 5 years of age, and clinical assessments at 1 and 5 years of age. Biological samples will also be collected for future immunological studies.

ANALYSIS PRIMARY OUTCOME

The proportion of participants with measures of allergy and infection (atopic sensitisation, eczema, lower respiratory tract infection) at 1 and 5 years of age, and asthma at 5 years of age.

SECONDARY OUTCOMES

(1) the proportion of participants with additional measures of allergy, eczema, asthma and infections; (2) medication use for eczema and asthma; (3) the severity and age of onset of eczema and asthma; (4) the number of episodes of infection; (5) hospitalisations for infections and (6) laboratory measures of immune responses.

ETHICS AND DISSEMINATION

This trial has ethical and governance approval from Mercy Health Human Research Ethics Committee (HREC, No. R12-28) and Royal Children's Hospital HREC (No. 33025) with additional governance approval from Barwon Health and St John of God, Geelong, Victoria. Results of this trial will be published in peer-reviewed journals and presented at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT01906853.

Heterologous Immunity: Role in Natural and Vaccine-Induced Resistance to Infections

The central paradigm of vaccination is to generate resistance to infection by a specific pathogen when the vacinee is re-exposed to that pathogen. This paradigm is based on two fundamental characteristics of the adaptive immune system, specificity and memory. These characteristics come from the clonal specificity of T and B cells and the long-term survival of previously-encountered memory cells which can rapidly and specifically expand upon re-exposure to the same specific antigen. However, there is an increasing awareness of the concept, as well as experimental documentation of, heterologous immunity and cross-reactivity of adaptive immune lymphocytes in protection from infection. This awareness is supported by a number of human epidemiological studies in vaccine recipients and/or individuals naturally-resistant to certain infections, as well as studies in mouse models of infections, and indeed theoretical considerations regarding the disproportional repertoire of available T and B cell clonotypes compared to antigenic epitopes found on pathogens. Heterologous immunity can broaden the protective outcomes of vaccinations, and natural resistance to infections. Besides exogenous microbes/pathogens and/or vaccines, endogenous microbiota can also impact the outcomes of an infection and/or vaccination through heterologous immunity. Moreover, utilization of viral and/or bacterial vaccine vectors, capable of inducing heterologous immunity may also influence the natural course of many infections/diseases. This review article will briefly discuss these implications and redress the central dogma of specificity in the immune system.

Out-of-sequence DTP and measles vaccinations and child mortality in Guinea-Bissau: a reanalysis

OBJECTIVES

To assess whether the sequence of diphtheria-tetanus-pertussis vaccine (DTP) and measles vaccine (MV) was associated with child survival in a dataset previously used to assess non-specific effects of vaccines with no consideration of vaccination sequence.

DESIGN

Prospective cohort study analysed using the landmark approach.

SETTING

Bandim Health Project's Health and Demographic Surveillance System covering 100 village clusters in rural Guinea-Bissau. The recommended vaccination schedule was BCG and oral polio vaccine (OPV) at birth, DTP and OPV at 6, 10 and 14 weeks, MV at 9 months and booster DTP and OPV at 18 months of age.

PARTICIPANTS

Children aged 9-17 months (main analysis) and 18-35 months (secondary analysis: age of booster DTP) with vaccination status assessed between April 1991 and April 1996.

METHODS

Survival during the 6 months after assessing vaccination status was compared by vaccination sequence in Cox-proportional hazards models with age as underlying time. Analyses were stratified by sex and village cluster.

MAIN OUTCOME MEASURE

Mortality rate ratio (MRR) for out-of-sequence vaccinations compared with in-sequence vaccinations.

RESULTS

Among children aged 9-17 months, 60% of observations (3574/5937) were from children who had received both MV and DTP. Among these, 1590 observations were classified as in-sequence vaccinations (last DTP before MV), and 1984 observations were out-of-sequence vaccinations (1491: MV with DTP and 493: MV before DTP). Out-of-sequence vaccinations were associated with higher mortality than in-sequence vaccinations (MRR 2.10, 95% CI 1.07 to 4.11); the MRR was 2.30 (95% CI 1.15 to 4.58) for MV with DTP and 1.45 (95% CI 0.50 to 4.22) for DTP after MV. Associations were similar for boys and girls (p=0.77). Between 18 and 35 months the mortality rate increased among children vaccinated in-sequence and the differential effect of out-of-sequence vaccinations disappeared.

CONCLUSION

Out-of-sequence vaccinations may increase child mortality. Hence, sequence of vaccinations should be considered when planning vaccination programmes or introducing new vaccines into the current vaccination schedule.

Developing the concept of beneficial non-specific effect of live vaccines with epidemiological studies

BACKGROUND

Epidemiological and immunological studies are increasingly reporting non-specific effects (NSEs) of vaccines; i.e. vaccines may affect the risk and severity of non-targeted infections. We reviewed how epidemiological studies developed the concept of beneficial NSEs of live vaccines.

SOURCES

This is a personal narrative of how we came to pursue the concept of NSEs in studies of measles vaccine (MV) from the late 1970s. We also searched Pubmed for epidemiological studies of nonspecific/non-specific effects (NSEs) of the most common human vaccines.

CONTENT

When smallpox vaccine was introduced around 1800, bacillus Calmette-Guérin (BCG) against tuberculosis in the 1920s and oral polio vaccine (OPV) in the 1960s, there were suggestions that these live attenuated vaccines reduced mortality more than expected. However, scientific follow-up was limited and the concept of beneficial NSEs did not become mainstream. We observed beneficial NSEs after MV was introduced in low-income countries in the 1970s. Subsequent observational studies and randomized trials confirmed beneficial NSEs of smallpox vaccine, BCG and OPV. Recently, beneficial NSEs have been claimed for the non-live diphtheria-tetanus-pertussis and rabies vaccines. However, no non-live vaccine has yet been documented to produce beneficial NSEs.

IMPLICATIONS

Observational and experimental research has shown beneficial NSEs of four live attenuated vaccines: smallpox vaccine, BCG, OPV and MV. With immunological evidence now supporting the epidemiological observations, it is urgent to take both the specific and NSEs into account in the planning of vaccination programmes.

Two Randomized Trials of the Effect of the Russian Strain of Bacillus Calmette-Guérin Alone or With Oral Polio Vaccine on Neonatal Mortality in Infants Weighing <2000 g in India

BACKGROUND

In randomized trials in Guinea-Bissau, the Danish strain of Bacillus Calmette-Guérin (BCG) reduces neonatal mortality, primarily by reducing deaths from pneumonia and sepsis. Because World Health Organization-prequalified BCG-Denmark was not available in India, we conducted 2 randomized trials to test whether BCG-Russia alone or with oral polio vaccine (OPV) has similar effects to BCG-Denmark.

METHODS

We randomized neonates weighing <2000 g to a control group that was not vaccinated before 28 days of age or to receive either BCG-Russia alone (first trial) or BCG-Russia with OPV (second trial) soon after birth. We performed intention-to-treat analysis using Cox hazards models with age as the underlying time and adjusted for weight, sex and inborn versus outborn status.

RESULTS

Administration of BCG-Russia alone had no effect on neonatal mortality (to 28 days of age): 15.6% of 1537 infants died in the BCG-Russia group and 16.1% of 1535 died in the control group; the adjusted hazard ratio was 0.95 [95% confidence interval (CI): 0.80-1.13]. Administration of BCG-Russia with OPV also had no effect on neonatal mortality: 18.0% of 1103 infants died in the BCG-OPV group and 17.6% of 1104 died in the control group; the adjusted hazard ratio was 1.01 (95% CI: 0.83-1.23). The adjusted hazard ratio for the 2 trials combined was 0.98 (95% CI: 0.85-1.11).

CONCLUSIONS

BCG-Russia with or without OPV had no effect on neonatal mortality. It is important to determine which strains of BCG have the greatest specific effects (on tuberculosis) and nonspecific effects (on infections other than tuberculosis) in high-mortality regions.

Observational studies of non-specific effects of Diphtheria-Tetanus-Pertussis vaccines in low-income countries: Assessing the potential impact of study characteristics, bias and confounding through meta-regression

INTRODUCTION

It has been suggested that some vaccines have effects beyond protection against the diseases they target, called non-specific effects (NSEs). In 2016, a systematic review by Higgins et al., commissioned by the WHO Strategic Advisory Group of Experts (SAGE) on immunization, estimated the relative risk (RR) of all-cause mortality after whole-cell Diphtheria-Tetanus-Pertussis (DTwP) vaccination to be 1.38 (95% CI: 0.92-2.08), and described these potential NSEs as inconsistent. However, the selection of studies for meta-analysis, based on their proneness to bias and confounding, was debated.

OBJECTIVE

To identify study characteristics and postulated risks of bias and confounding that might have impacted the RR of all-cause mortality after DTwP vaccination in observational studies conducted in low-income countries.

METHODS

Based on methodological considerations on study design and analysis, we systematically assessed all 17 DTwP studies from the Higgins et al. review for risk of selection bias, exposure and outcome misclassification, confounding and differential co-interventions. We used meta-regression to assess the impact of study characteristics and the postulated risks of bias and confounding on the RR estimates, and looked for outlying and influential risk estimates. Permutation tests were performed to control for false-positive findings.

RESULTS

The overall RR of all-cause mortality after DTwP vaccination including all but one outlying and influential study was 1.32 (95% CI: 0.83-2.08). Based on uni-variable meta-regression, we found that study location (p = 0.01), studies using the landmark approach (p = 0.015) and studies at high risk of exposure misclassification (p = 0.036) were significantly associated with increased RR estimates whereas studies at high risk of selection bias (p = 0.059) showed borderline significance. The results further suggest these effect modifiers are clustered in studies conducted in West-Africa.

CONCLUSION

The increased RR of all-cause mortality after DTwP might be confined to West-African countries and/or certain postulated risks of bias might have inflated these RRs.

Impact of monovalent rotavirus vaccine on diarrhoea-associated post-neonatal infant mortality in rural communities in Malawi: a population-based birth cohort study

BACKGROUND

Rotavirus is a major contributor to child mortality. The effect of rotavirus vaccine on diarrhoea mortality has been estimated in middle-income but not low-income settings, where mortality is high and vaccine effectiveness in reducing admissions to hospital is lower. Empirical population-based mortality studies have not been done in any setting. Malawi introduced monovalent rotavirus vaccine (RV1) in October, 2012. We aimed to investigate the impact and effectiveness of the RV1 vaccine in reducing diarrhoea-associated mortality in infants aged 10-51 weeks.

METHODS

In this population-based cohort study, we included infants born between Jan 1, 2012, and June 1, 2015, in Mchinji, Central Malawi and analysed data on those surviving 10 weeks. Individual vaccination status was extracted from caregiver-held records or report at home visits at 4 months and 1 year of age. Survival to 1 year was confirmed at home visit, or cause of death ascertained by verbal autopsy. We assessed impact (1 minus mortality rate ratio following vs before vaccine introduction) using Poisson regression. Among vaccine-eligible infants (born from Sept 17, 2012), we assessed effectiveness (1 minus hazard ratio) using Cox regression.

FINDINGS

Between Jan 1, 2012, and June 1, 2015, we recruited 48 672 livebirths in Mchinji, among whom 38 518 were vaccine-eligible and 37 570 survived to age 10 weeks. Two-dose versus zero-dose effectiveness analysis included 28 141 infants, of whom 101 had diarrhoea-associated death before 1 year of age. Diarrhoea-associated mortality declined by 31% (95% CI 1-52; p=0·04) after RV1 introduction. Effectiveness against diarrhoea-mortality was 34% (95% CI -28 to 66; p=0·22).

INTERPRETATION

RV1 was associated with substantial reduction in diarrhoea-associated deaths among infants in this rural sub-Saharan African setting. These data add considerable weight to evidence showing the impact of rotavirus vaccine programmes.

FUNDING

Wellcome Trust and GlaxoSmithKline Biologicals.

Effect of sex on vaccination outcomes: important but frequently overlooked

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

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.

How to evaluate potential non-specific effects of vaccines: the quest for randomized trials or time for triangulation?

INTRODUCTION

Emerging evidence suggests that vaccines, in addition to their disease-specific effects, have important non-specific effects (NSEs), which contribute to their overall effect on mortality and morbidity. Immunological studies have shown that NSEs are biologically plausible. Many advocate that randomized controlled trials (RCTs) with overall mortality or morbidity as the outcome are the only way forward to confirm or refute NSEs.

AREAS COVERED

We discuss the limitations of using RCTs only as a tool to evaluate NSEs of vaccines. Such RCTs can be ethically problematic, they are time consuming and expensive. Furthermore, they only assess the NSEs in a given context, but it is inherent in the concept of NSEs that the NSEs of a given vaccine are modified by other immunomodulatory conditions. As an alternative, we propose that triangulation of RCTs and observational studies, merging multiple lines of evidence with different underlying bias structures, can build a strong argument for causality. We examine two examples related to measles vaccine and oral polio vaccine.

EXPERT COMMENTARY

Using RCTs alone to evaluate NSEs of vaccines severely limits the possibilities for studying NSEs. Results from both RCTs and non-RCT studies should be triangulated to strengthen causal interpretation.

Evidence of Increase in Mortality After the Introduction of Diphtheria-Tetanus-Pertussis Vaccine to Children Aged 6-35 Months in Guinea-Bissau: A Time for Reflection?

Background

Whole-cell diphtheria–tetanus–pertussis (DTP) and oral polio vaccine (OPV) were introduced to children in Guinea-Bissau in 1981. We previously reported that DTP in the target age group from 3 to 5 months of age was associated with higher overall mortality. DTP and OPV were also given to older children and in this study we tested the effect on mortality in children aged 6–35 months.

Methods

In the 1980s, the suburb Bandim in the capital of Guinea-Bissau was followed with demographic surveillance and tri-monthly weighing sessions for children under 3 years of age. From June 1981, routine vaccinations were offered at the weighing sessions. We calculated mortality hazard ratio (HR) for DTP-vaccinated and DTP-unvaccinated children aged 6–35 months using Cox proportional hazard models. Including this study, the introduction of DTP vaccine and child mortality has been studied in three studies; we made a meta-estimate of these studies.

Results

At the first weighing session after the introduction of vaccines, 6–35-month-old children who received DTP vaccination had better weight-for-age z-scores (WAZ) than children who did not receive DTP; one unit increase in WAZ was associated with an odds ratio of 1.32 (95% CI = 1.13–1.55) for receiving DTP vaccination. Though lower mortality compared with not being DTP-vaccinated was, therefore, expected, DTP vaccination was associated with a non-significant trend in the opposite direction, the HR being 2.22 (0.82–6.04) adjusted for WAZ. In a sensitivity analysis, including all children weighed at least once before the vaccination program started, DTP (±OPV) as the most recent vaccination compared with live vaccines or no vaccine was associated with a HR of 1.89 (1.00–3.55). In the three studies of the introduction of DTP in rural and urban Guinea-Bissau, DTP-vaccinated children had an HR of 2.14 (1.42–3.23) compared to DTP-unvaccinated children; this effect was separately significant for girls [HR = 2.60 (1.57–4.32)], but not for boys [HR = 1.71 (0.99–2.93)] (test for interaction p = 0.27).

Conclusion

Although having better nutritional status and being protected against three infections, 6–35 months old DTP-vaccinated children tended to have higher mortality than DTP-unvaccinated children. All studies of the introduction of DTP have found increased overall mortality.

Revised World Health Organization (WHO)'s causality assessment of adverse events following immunization-a critique

The World Health Organisation (WHO) has recently revised how adverse events after immunization (AEFI) are classified. Only reactions that have previously been acknowledged in epidemiological studies to be caused by the vaccine are classified as a vaccine-product–related-reaction. Deaths observed during post-marketing surveillance are not considered as ‘consistent with causal association with vaccine’, if there was no statistically significant increase in deaths recorded during the small Phase 3 trials that preceded it. Of course, vaccines  noted to have caused a significant increase in deaths in the control-trials stage would probably not be licensed. After licensure, deaths and all new serious adverse reactions are labelled as ‘coincidental deaths/events’ or ‘unclassifiable’, and the association with vaccine is not acknowledged. The resulting paradox is evident.

The definition of causal association has also been changed. It is now used only if there is ‘no other factor intervening in the processes’. Therefore, if a child with an underlying congenital heart disease (other factor), develops fever and cardiac decompensation after vaccination, the cardiac failure would not be considered causally related to the vaccine. The Global Advisory Committee on Vaccine Safety has documented many deaths in children with pre-existing heart disease after they were administered the pentavalent vaccine. The WHO now advises precautions when vaccinating such children. This has reduced the risk of death. Using the new definition of causal association, this relationship would not be acknowledged and lives would be put at risk. In view of the above, it is necessary that the AEFI manual be revaluated and revised urgently. AEFI reporting is said to be for vaccine safety. Child safety (safety of children) rather than vaccine safety (safety for vaccines) needs to be the emphasis.

Revised World Health Organization (WHO)'s causality assessment of adverse events following immunization-a critique

The World Health Organisation (WHO) has recently revised how adverse events after immunization (AEFI) are classified. Only reactions that have previously been acknowledged in epidemiological studies to be caused by the vaccine are classified as a vaccine-product-related-reaction. Deaths observed during post-marketing surveillance are not considered as 'consistent with causal association with vaccine', if there was no statistically significant increase in deaths recorded during the small Phase 3 trials that preceded it. Of course, vaccines  noted to have caused a significant increase in deaths in the control-trials stage would probably not be licensed. After licensure, deaths and all new serious adverse reactions are labelled as 'coincidental deaths/events' or 'unclassifiable', and the association with vaccine is not acknowledged. The resulting paradox is evident. The definition of causal association has also been changed. It is now used only if there is 'no other factor intervening in the processes'. Therefore, if a child with an underlying congenital heart disease (other factor), develops fever and cardiac decompensation after vaccination, the cardiac failure would not be considered causally related to the vaccine. The Global Advisory Committee on Vaccine Safety has documented many deaths in children with pre-existing heart disease after they were administered the pentavalent vaccine. The WHO now advises precautions when vaccinating such children. This has reduced the risk of death. Using the new definition of causal association, this relationship would not be acknowledged and lives would be put at risk. In view of the above, it is necessary that the AEFI manual be revaluated and revised urgently. AEFI reporting is said to be for vaccine safety. Child safety (safety of children) rather than vaccine safety (safety for vaccines) needs to be the emphasis.

Effects of Bacillus Calmette-Guérin (BCG) vaccination at birth on T and B lymphocyte subsets: Results from a clinical randomized trial

The Bacillus Calmette–Guérin vaccine (BCG) has been associated with beneficial non-specific effects (NSEs) on infant health. Within a randomized trial on the effect of neonatal BCG on overall health, we investigated the possible immunological impact of neonatal BCG vaccination on lymphocyte subsets, determined by flow cytometry. In 118 infants blood samples were obtained 4 (±2) days post randomization to BCG vaccination or no intervention, and at 3 and 13 months of age. No effects of BCG were found at 4 days. However, BCG increased proportions of effector memory cells at 3 months (Geometric mean ratio (GMR) 1.62, 95% confidence interval (CI) (1.20–2.21), p = 0.002 for CD4⁺ T cells and GMR 1.69, 95% CI (1.06–2.70), p = 0.03 for CD8⁺ T cells), and reduced proportions of late differentiated CD4⁺ T cells (GMR = 0.62, 95% CI (0.38–1.00), p = 0.05) and apoptotic CD4⁺ T cells at 13 months (GMR = 0.55, 95% CI (0.32–0.92), p = 0.03). In conclusion, limited overall impact of neonatal BCG vaccination on lymphocyte subsets was found in healthy Danish infants within the first 13 months of life. This is in line with the limited clinical effects of BCG observed in our setting.

Vaccinations in the first year of life and risk of atopic disease - Results from the KiGGS study

BACKGROUND

The study focused on the question of whether and - if so - to what direction and extent immunisations in the 1st year may be associated with the risk of being diagnosed with atopic diseases after the 1st year of life.

METHODS

Data from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS, 2003-2006) were analysed. For analyses of potential associations between vaccination status and risk of hay fever, atopic dermatitis or asthma, sample sizes of 15254, 14297, and 15262, respectively, were available.

RESULTS

Children with a sufficient TDPHiHeP vaccination at the end of the 1st year of life had a lower risk of being diagnosed with hay fever after the 1st year of life (adjusted prevalence ratio 0.85, 95% confidence interval 0.76-0.96). Analyses for associations between TDPHiHeP vaccination and risk of atopic dermatitis or asthma, or between age at onset of vaccination or of the number of antigens vaccinated in the 1st year of life and risk of atopic disease failed to yield statistical significance.

CONCLUSIONS

Our results provide no evidence that immunisations in the 1st year of life may increase the risk of atopic disease. If any association exists at all, our results may be interpreted as weakly supportive of the hypothesis that immunisations may slightly decrease the risk of atopy in later life.

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.

Co-administration of BCG and Diphtheria-tetanus-pertussis (DTP) Vaccinations May Reduce Infant Mortality More Than the WHO-schedule of BCG First and Then DTP. A Re-analysis of Demographic Surveillance Data From Rural Bangladesh

BACKGROUND

WHO recommends BCG at birth and diphtheria-tetanus-pertussis (DTP)-containing vaccine at 6, 10 and 14weeks of age. However, BCG and DTP are often co-administered in low-income countries. The health implications have not been examined.

SETTING

We reanalysed data from Matlab, Bangladesh, to examine the influence of co-administration on mortality; 37,894 children born 1986-1999 were followed with registration of vaccinations and survival.

METHODS

Using Cox models, survival was analysed from 6weeks to 9months of age when measles vaccine is given; 712 children died in this age group. We calculated mortality rate ratios (MRR) for children starting the vaccination schedule with BCG-first, BCG+DTP1-first or DTP1-first.

RESULTS

Only 17% followed the WHO-schedule with BCG-first. Mortality was 16/1000 person-years for children who initiated the vaccination schedule with BCG+DTP1 but 32/1000 and 20/1000 for children who received BCG-first or DTP-first, respectively. Compared with BCG+DTP1-first and adjusting for background factors, the BCG-first-schedule was associated with 2-fold higher mortality (MRR=1.94 (1.42-2.63)). DTP1 administered after BCG-first was associated with higher mortality than receiving DTP1 with BCG (MRR=1.78 (1.03-3.03)).

CONCLUSIONS

Co-administration of BCG and DTP may further reduce mortality. Since all observational studies support this trend, co-administration of BCG and DTP should be tested in randomised trials.

Analysis of risk factors for infant mortality in the 1992-3 and 2002-3 birth cohorts in rural Guinea-Bissau

Introduction

Though still high, the infant mortality rate in Guinea-Bissau has declined. We aimed to identify risk factors including vaccination coverage, for infant mortality in the rural population of Guinea-Bissau and assess whether these risk factors changed from 1992–3 to 2002–3.

Methods

The Bandim Health Project (BHP) continuously surveys children in rural Guinea-Bissau. We investigated the association between maternal and infant factors (especially DTP and measles coverage) and infant mortality. Hazard ratios (HR) were calculated using Cox regression. We tested for interactions with sex, age groups (defined by current vaccination schedule) and cohort to assess whether the risk factors were the same for boys and girls, in different age groups in 1992–3 and in 2002–3.

Results

The infant mortality rate declined from 148/1000 person years (PYRS) in 1992–3 to 124/1000 PYRS in 2002–3 (HR = 0.88;95%CI:0.77–0.99); this decline was significant for girls (0.77;0.64–0.94) but not for boys (0.97;0.82–1.15) (p = 0.10 for interaction). Risk factors did not differ significantly by cohort in either distribution or effect. Mortality decline was most marked among girls aged 9–11 months (0.56;0.37–0.83). There was no significant mortality decline for girls 1.5–8 months of age (0.93;0.68–1.28) (p = 0.05 for interaction). DTP and measles coverage increased from 1992–3 to 2002–3.

Conclusions

Risk factors did not change with the decline in mortality. Due to beneficial non-specific effects for girls, the increased coverage of measles vaccination may have contributed to the disproportional decline in mortality by sex and age group.

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.

Fewer out-of-sequence vaccinations and reduction of child mortality in Northern Ghana

BACKGROUND

Studies suggest that diphtheria-tetanus-pertussis (DTP) vaccine administered simultaneously with measles vaccine (MV) or DTP administered after MV are associated with higher child mortality than having MV-after-DTP3 as most recent vaccination. We tested this in Northern Ghana where the prevalence of such out-of-sequence vaccinations has declined.

METHODS

Using annual cohort data of children aged 12-23months from 1996 to 2012 and Cox proportional hazards models, we assessed survival in relation to the most recent vaccination status within the next 12months and until five years of age. We assessed whether mortality in children aged 12-59months was higher when the most recent vaccine was non-live (DTP) rather than live (MV or OPV).

RESULTS

Out-of-sequence vaccinations with DTP-containing vaccines and MV declined from 86% in 1989 to 24% in 1996 and 0.7% in 2012. Between 1996 and 2012, 38 070 children had their vaccinations status assessed: the adjusted hazard ratio (HR) for out-of-sequence vaccinations (DTP>=MV) compared with the recommended sequence of MV-after-DTP3 was 1.42(1.06-1.90) during the first 12months after assessment of vaccination status and 1.29(1.03-1.60) with follow-up to five years of age; the HR was 2.58(1.14-5.84) before OPV or MV campaigns and 1.37(1.02-1.85) after the campaigns.

CONCLUSION

Out-of-sequence vaccinations with DTP and MV are associated with higher mortality than MV as most recent vaccination; the effect is unlikely to be due to confounding. Hence, the reduction in out-of-sequence vaccinations may have lowered child mortality. It is recommended not to give DTP with MV or DTP after MV.

The Introduction of Diphtheria-Tetanus-Pertussis and Oral Polio Vaccine Among Young Infants in an Urban African Community: A Natural Experiment

BACKGROUND

We examined the introduction of diphtheria-tetanus-pertussis (DTP) and oral polio vaccine (OPV) in an urban community in Guinea-Bissau in the early 1980s.

METHODS

The child population had been followed with 3-monthly nutritional weighing sessions since 1978. From June 1981 DTP and OPV were offered from 3months of age at these sessions. Due to the 3-monthly intervals between sessions, the children were allocated by birthday in a 'natural experiment' to receive vaccinations early or late between 3 and 5months of age. We included children who were <6months of age when vaccinations started and children born until the end of December 1983. We compared mortality between 3 and 5months of age of DTP-vaccinated and not-yet-DTP-vaccinated children in Cox proportional hazard models.

RESULTS

Among 3-5-month-old children, having received DTP (±OPV) was associated with a mortality hazard ratio (HR) of 5.00 (95% CI 1.53-16.3) compared with not-yet-DTP-vaccinated children. Differences in background factors did not explain the effect. The negative effect was particularly strong for children who had received DTP-only and no OPV (HR=10.0 (2.61-38.6)). All-cause infant mortality after 3months of age increased after the introduction of these vaccines (HR=2.12 (1.07-4.19)).

CONCLUSION

DTP was associated with increased mortality; OPV may modify the effect of DTP.

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.

Sex-differential effects on mortality of BCG and diphtheria-tetanus-pertussis vaccines in a rural area with high vaccination coverage: observational study from Senegal

BACKGROUND

Diphtheria-tetanus-pertussis (DTP) may be associated with increased female mortality; the effect of co-administration with BCG is not known.

METHODS

Between 1989 and 1997, we examined female and male mortality rates in rural Senegal where 7824 infants received the first dose of DTP and inactivated polio vaccine (DTP-IPV) with BCG. Subsequent doses of DTP-IPV were administered alone. We analysed mortality according to sex and number of doses of DTP-IPV vaccine.

RESULTS

BCG and DTP-IPV1 simultaneously reduced mortality from 60/1000 person-years in unvaccinated girls to 35/1000 person-years, but mortality increased with subsequent doses of DTP-IPV to 45/1000 person-years. Among boys, BCG and DTP-IPV1 simultaneously reduced mortality from 72/1000 person-years to 60/1000 person-years and mortality decreased further with subsequent doses of DTP-IPV to 34/1000 person-years. In age-adjusted analyses, female-male mortality rate ratios were 0.83(95% CI 0.50-1.40) among unvaccinated children and 0.58 (95% CI 0.35-0.96) among children vaccinated simultaneously with BCG and DTP-IPV1, but increased to 1.17 (95% CI 0.67-2.03) after DTP-IPV2, and 1.63 (95% CI 0.86-3.10) after DTP-IPV3. Difference in vaccination coverage could not explain these sex-differential patterns; girls had significantly better weight-for-age than boys so nutritional status did not explain the increase in female mortality after DTP-IPV3.

CONCLUSIONS

Whereas BCG co-administered with DTP-IPV was associated with lower female than male mortality, subsequent DTP-IPV vaccinations were associated with an increase in female mortality relative to male mortality.

Revaccination with Live Attenuated Vaccines Confer Additional Beneficial Nonspecific Effects on Overall Survival: A Review

BACKGROUND

Live vaccines against measles (MV), tuberculosis (BCG), polio (OPV) and smallpox reduce mortality more than explained by target-disease prevention. The beneficial nonspecific effects (NSEs) of MV are strongest when MV is given in presence of maternal antibodies. We therefore hypothesised that revaccination in presence of prior immunity enhances beneficial NSEs.

METHODS

Literature search for studies of revaccination and mortality.

FINDINGS

In two randomised trials (RCTs), two doses versus one dose of MV reduced all-cause mortality by 63% (95% CI: 23-83%) from 9 to 18months of age. In a quasi-experimental study two doses before and after 9months compared with one dose of MV after 9months of age reduced mortality by 59% (25-81%). BCG-revaccination significantly enhanced BCG's effect against overall child mortality in two RCTs. In a natural experiment study of OPV campaigns over a 13-year-period in Guinea-Bissau, each additional dose of OPV was associated with a 13% (4-21%) reduction in mortality rate. The beneficial NSEs of smallpox vaccination for survival increased significantly with the number of smallpox vaccination scars.

INTERPRETATION

Revaccination with live vaccines led to substantial reductions in overall mortality. These findings challenge current understanding of vaccines and may explain the beneficial effects of campaigns with live vaccines.

Contrasting female-male mortality ratios after routine vaccinations with pentavalent vaccine versus measles and yellow fever vaccine. A cohort study from urban Guinea-Bissau

BACKGROUND

In addition to protection against the target diseases, vaccines may have non-specific effects (NSEs). Measles vaccine (MV) has beneficial NSEs, providing protection against non-measles deaths, most so for girls. By contrast, though protecting against diphtheria, tetanus and pertussis, DTP vaccine is associated with increased female mortality relative to male mortality. In 2008, Guinea-Bissau replaced DTP with the DTP-containing pentavalent vaccine (Penta; DTP-H. influenza type B-Hepatitis B) at 6, 10 and 14weeks and yellow fever vaccine (YF) was to be given with MV. We investigated possible sex-differential mortality rates following Penta and MV+YF vaccination.

METHODS

Bandim Health Project (BHP) registers vaccines given by the three government health centres in the study area and vital status through demographic surveillance. We assessed the association between sex and mortality by vaccination status in Cox proportional hazards models with age as underlying timescale. Follow-up was censored at a subsequent vaccination contact or after 6months of follow-up.

RESULTS

Between September 2008 and April 2011, we registered 23,448 vaccination contacts for children aged 42-365days; 17,313 were for Penta and 3028 for MV (2907 co-administered with YF). During follow-up 112 children died. The female/male mortality rate ratio was 1.73 (1.11-2.70) following Penta and 0.38 (0.12-1.19) after MV (p=0.02 for same effect). Adjusting for maternal education or weight-for-age at the time of vaccination did not change the estimates.

CONCLUSION

Penta appears to have the same negative effects on mortality as those seen for DTP. Assessing post-vaccination mortality for boys and girls is necessary to improve the vaccination programme.

Sex-Differential Non-Vaccine-Specific Immunological Effects of Diphtheria-Tetanus-Pertussis and Measles Vaccination

Vaccines can have nontargeted heterologous effects that manifest as increased protection against nonvaccine infections, as described for measles vaccine (MV), or increased susceptibility to infections and death, as described following diphtheria-tetanus-whole cell pertussis (DTP) vaccination. The mechanisms are unknown, and high-quality immunological studies are lacking. This study was designed to investigate the heterologous effects of MV and DTP in 302 Gambian infants. The results support a sex-differential immunosuppressive effect of DTP on innate proinflammatory responses and T-cell immunity. Males but not females receiving MV had enhanced proinflammatory innate responses. The results point to modified signaling via Toll-like receptor 4 (TLR4) as a possible mechanism for the effects on innate immunity. When both vaccines were administered together, purified protein derivative responses were enhanced in females but downregulated in males. Collectively, these data indicate immunological effects that could account for heterologous effects of MV and DTP, to take forward into prospective trials.