Campaigns with oral polio vaccine may lower mortality and create unexpected results

Effect of a campaign with oral polio vaccine on general health: A cluster-randomised trial in rural Guinea-Bissau

OBJECTIVES

To investigate in a cluster-randomised trial whether a campaign with oral polio vaccine (C-OPV) reduced mortality and morbidity.

METHODS

We randomised 222 village clusters under demographic surveillance to an intervention (health check and C-OPV) or control group (health check only). Children aged 0-8 months were eligible. In Cox proportional hazards models with age as the underlying timescale, we compared rates of non-accidental mortality/hospital admission (composite primary outcome) during 12 months of follow-up. Secondary analyses considered non-accidental admission and mortality as separate outcomes. Potential effect modifiers identified in prior studies including sex, season, and timing of the first routine OPV dose (OPV0, scheduled at birth) were assessed.

RESULTS

Among 10,175 children (5288 in 111 intervention clusters/4887 in 111 control clusters), we observed 265 deaths/admissions during 7616 person-years at risk (intervention: 129; control: 136). C-OPV did not reduce the composite endpoint, hazard ratio (HR): 0.87, 95%CI: 0.68-1.12 or its separate components. C-OPV reduced the risk in children receiving OPV0<15 days of birth (HR=0.66, 95%CI: 0.46-0.95), but not in other children (p for interaction: 0.03). Interactions for other potential effect modifiers were not statistically significant.

CONCLUSIONS

C-OPV had no overall effect on mortality/admissions, but the effect differed by early priming with OPV0.

Characterization of "Off-Target" Immune Modulation Induced by Live Attenuated Yellow Fever Vaccine

BACKGROUND

Live attenuated vaccines alter immune functions and are associated with beneficial outcomes. We previously demonstrated that live attenuated yellow fever virus (YFV) vaccine (LA-YF-Vax) dampens T-cell receptor (TCR) signaling in vitro via an RNA-based mechanism. We examined study participants before and after LA-YF-Vax to assess TCR-mediated functions in vivo.

METHODS

Serum samples and peripheral blood mononuclear cells (PBMCs) were obtained before and after LA-YF-Vax (with or without additional vaccines) or quadrivalent influenza vaccine. TCR-mediated activation was determined by interleukin 2 release or phosphorylation of the lymphocyte-specific Src kinase. TCR-regulating phosphatase (protein tyrosine phosphatase receptor type E [PTPRE]) expression was also measured.

RESULTS

Compared with prevaccination findings, LA-YF-Vax recipient PBMCs demonstrated transient reduction in interleukin 2 release after TCR stimulation and PTPRE levels, unlike in control participants who received quadrivalent influenza vaccine. YFV was detected in 8 of 14 participants after LA-YF-Vax. After incubation of healthy donor PBMCs in serum-derived extracellular vesicles prepared from LA-YF-Vax recipients, TCR signaling and PTPRE levels were reduced after vaccination, even in participants without detectable YFV RNA.

CONCLUSIONS

LA-YF-Vax reduces TCR functions and PTPRE levels after vaccination. Extracellular vesicles from serum recapitulated this effect in healthy cells. This likely contributes to the reduced immunogenicity for heterologous vaccines after LA-YF-Vax administration. Identification of specific immune mechanisms related to vaccines should contribute to understanding of the "off-target," beneficial effects of live vaccines.

Determinants of neonatal, infant and under-five mortalities: evidence from a developing country, Bangladesh

We investigated the macroeconomic determinants of neonatal, infant, and under-five mortalities in Bangladesh for the period 1991-2018 and discuss implications of the United Nations' Sustainable Development Goal 3 (SDG 3) and Millennium Development Goal 4 (MDG 4) for developing countries. We used annual time series data and the econometric techniques of Fully Modified Ordinary Least Squares (FMOLS) and Dynamic Ordinary Least Squares (DOLS) regressions for analysis. Determinants most effective in combating neonatal, infant, and under-five mortalities include variables such as 'protecting newborns against tetanus', 'increasing healthcare expenditure', and 'making sure births are attended by skilled healthcare staff'. Employing more healthcare workers and assuring more and improved healthcare provisions can further reduce the neonatal, infant, and under-five mortalities. Developing countries with similar macroeconomic profiles can achieve similar SDG 3 and MDG 4 outcomes by emulating the policies and strategies Bangladesh applied to reducing child mortalities over the last three decades.

The Effect of a Second Dose of Measles Vaccine at 18 Months of Age on Nonaccidental Deaths and Hospital Admissions in Guinea-Bissau: Interim Analysis of a Randomized Controlled Trial

BACKGROUND

The world is set on the eradication of measles. Continuation of the measles vaccine (MV) after eradication could still reduce morbidity because the MV has so-called beneficial nonspecific effects. We evaluated the effect of a "booster" dose of the MV on overall severe morbidity.

METHODS

We conducted a randomized controlled trial among children aged 17.5 to 48 months in Guinea-Bissau, where the MV is recommended only at 9 months of age. At the time of this interim analysis, 3164 children had been allocated 1:1 to a second dose of measles vaccine (MV2) at 18 months of age or to no vaccine. Severe morbidity (a composite outcome of nonaccidental deaths and hospital admissions) rate ratios (SMRRs) were calculated by Cox regression analysis censored for national oral polio vaccine (OPV) campaigns.

RESULTS

There were no measles cases during the trial period. There were 43 nonaccidental deaths or hospital admissions during follow-up. Severe morbidity was 2.6 per 100 person-years in the MV2 group and 3.6 per 100 person-years among controls; hence, the estimated effect of MV2 on severe morbidity was 28% (SMRR, 0.72; 95% confidence interval [CI], .38-1.38). At 12 months of follow-up, the number needed to treat to prevent 1 severe morbidity event was 137 children. After OPV campaigns, the estimated effect of MV2 was reduced to 9% (SMRR, 0.91; 95% CI, .46-1.81).

CONCLUSIONS

MV2 may reduce nonmeasles severe morbidity by 28% (-38% to 62%), although this did not achieve statistical significance in this study. If significant in higher powered studies, this has major implications for child health, even after measles eradication.

CLINICAL TRIALS REGISTRATION

NCT02943681.

Stopping Oral Polio Vaccine (OPV) After Defeating Poliomyelitis in Low- and Middle-Income Countries: Harmful Unintended Consequences? Review of the Nonspecific Effects of OPV

Background

The live vaccines bacille Calmette-Guérin (BCG) and measles vaccine have beneficial nonspecific effects (NSEs) reducing mortality, more than can be explained by prevention of tuberculosis or measles infection. Live oral polio vaccine (OPV) will be stopped after polio eradication; we therefore reviewed the potential NSEs of OPV.

Methods

OPV has been provided in 3 contexts: (1) coadministration of OPV and diphtheria-tetanus-pertussis (DTP) vaccine at 6, 10, and 14 weeks of age; (2) at birth (OPV0) with BCG; and (3) in OPV campaigns (C-OPVs) initiated to eradicate polio infection. We searched PubMed and Embase for studies of OPV with mortality as an outcome. We used meta-analysis to obtain the combined relative risk (RR) of mortality associated with different uses of OPV.

Results

First, in natural experiments when DTP was missing, OPV-only compared with DTP + OPV was associated with 3-fold lower mortality in community studies (RR, 0.33 [95% confidence interval {CI}, .14-.75]) and a hospital study (RR, 0.29 [95% CI, .11-.77]). Conversely, when OPV was missing, DTP-only was associated with 3-fold higher mortality than DTP + OPV (RR, 3.23 [95% CI, 1.27-8.21]). Second, in a randomized controlled trial, BCG + OPV0 vs BCG + no OPV0 was associated with 32% (95% CI, 0-55%) lower infant mortality. Beneficial NSEs were stronger with early use of OPV0. Third, in 5 population-based studies from Guinea-Bissau and Bangladesh, the mortality rate was 24% (95% CI, 17%-31%) lower after C-OPVs than before C-OPVs.

Conclusions

There have been few clinical polio cases reported in this century, and no confounding factors or bias would explain all these patterns. The only consistent interpretation is that OPV has beneficial NSEs, reducing nonpolio child mortality.

Infectious Diseases-Related Hospitalizations During Oral Polio Vaccine(OPV) and non-OPV immunization periods: An Empirical Evaluation of all Hospital Discharges in California(1985-2010)

BACKGROUND

Live attenuated vaccines such as oral polio vaccine (OPV) can stimulate innate immunity and may have off-target protective effects on other pathogens. We aimed to address this hypothesis by examining changes in infectious diseases (ID)-related hospitalizations in all hospital discharges in California during OPV-(1985-1996) and non-OPV-immunization periods (2000-2010).

METHODS

We searched the OSHPD (Office of Statewide Health Planning and Development) database for all hospital discharges with any ID-related discharge diagnosis code during 1985-2010. We compared the proportion of ID-related hospitalizations (with at least one ID-related discharge diagnosis) among total hospitalizations during OPV immunization (1985-1996) vs non-OPV immunization (2000-2010) periods.

RESULTS

There were 19,281,039 ID-related hospitalizations (8,464,037 with an ID-related discharge-diagnosis as the principal discharge diagnosis for the hospitalization) among 98,117,475 hospitalizations in 1985-2010; 9,520,810 ID-hospitalizations/43,456,484 total hospitalizations in 2000-2010 vs 7,526,957/43,472,796 in 1985-1996. The RR for ID-related hospitalizations in 2000-2010 vs 1985-1996 was 1.27(95% CI: 1.26-1.27) for all diagnoses and 1.15(95% CI: 1.15-1.16) for principal diagnoses. Increases also existed in the proportion of lower respiratory and gastrointestinal infections.

DISCUSSION

The proportion of ID-related hospitalizations was lower in the OPV-immunization period compared to the period after OPV was discontinued. When focused only on hospitalizations with ID as the principal discharge diagnosis the signal remained significant but was smaller. These findings require replication in additional studies.

A narrative review of nonspecific effects of pediatric vaccines on child mortality and morbidity

We reviewed evidence on nonspecific effects of pediatric vaccines on mortality and morbidity in countries with high child mortality. Literature search of epidemiological studies was conducted for studies published between 2000 and September 2021 using MEDLINE. Consistent evidence exists regarding the potential protective effect of measles vaccine on child survival. Vaccination with Bacillus Calmette-Guérin (BCG) vaccine was related to lower risk of mortality in young children (including low birth weight babies) and inverse associations were found between developing a scar and having a positive tuberculin test after BCG vaccination with mortality. BCG vaccine might also reduce the risk of nontuberculosis infectious diseases. Studies on the association between diphtheria-pertussis-tetanus (DPT) vaccine and child survival showed inconsistent findings, which might be affected by bias and confounding. More evidence is needed to assess the role of these and other vaccines in children's health and to better understand potential biological mechanisms and other influential factors.

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.

National Immunization Campaigns With Oral Polio Vaccine May Reduce All-cause Mortality: An Analysis of 13 Years of Demographic Surveillance Data From an Urban African Area

BACKGROUND

Between 2002 and 2014, Guinea-Bissau had 17 national campaigns with oral polio vaccine (OPV) as well as campaigns with vitamin A supplementation (VAS), measles vaccine (MV), and H1N1 influenza vaccine. We examined the impact of these campaigns on child survival.

METHODS

We examined the mortality rate between 1 day and 3 years of age of all children in the study area. We used Cox models with age as underlying time to calculate adjusted mortality rate ratios (MRRs) between "after-campaign" mortality and "before-campaign" mortality, adjusted for temporal change in mortality and stratified for season at risk.

RESULTS

Mortality was lower after OPV-only campaigns than before, with an MRR for after-campaign vs before-campaign being 0.75 (95% confidence interval [CI], .67-.85). Other campaigns did not have similar effects, the MRR being 1.22 (95% CI, 1.04-1.44) for OPV + VAS campaigns, 1.39 (95% CI, 1.20-1.61) for VAS-only campaigns, 1.32 (95% CI, 1.09-1.60) for MV + VAS campaigns, and 1.13 (95% CI, .86-1.49) for the H1N1 campaign. Thus, all other campaigns differed significantly from the effect of OPV-only campaigns. Effects did not differ for trivalent, bivalent, or monovalent strains of OPV. With each additional campaign of OPV only, the mortality rate declined further (MRR, 0.86 [95% CI, .81-.92] per campaign). With follow-up to 3 years of age, the number needed to treat to save 1 life with the OPV-only campaign was 50 neonates.

CONCLUSIONS

OPV campaigns can have a much larger effect on child survival than otherwise assumed. Stopping OPV campaigns in low-income countries as part of the endgame for polio infection may increase child mortality.

National immunisation campaigns with oral polio vaccine may reduce all-cause mortality: Analysis of 2004-2019 demographic surveillance data in rural Bangladesh

BACKGROUND

West African studies have suggested that national immunisation campaigns with oral polio vaccine (C-OPV) may non-specifically reduce all-cause child mortality rate by 15-25%. We investigated whether C-OPVs had similar non-specific effects in rural Bangladesh from 2004 to 2019.

METHODS

Chakaria, is a health and demographic surveillance system (HDSS) in Southern Bangladesh. From 2004-2011 the HDSS covered a random sample of households; from 2012 to 2019 it covered a random sample of villages. Using Cox proportional hazards models, we calculated hazard ratios (HR) comparing mortality for children under 3 years of age after C-OPV versus before C-OPV to assess the effect of receiving a C-OPV. We allowed for different baseline hazard function in the two periods (2004-2011, 2012-2019), with separate models for each period.

FINDINGS

There were 768 deaths (2.1%) amongst 36,176 children. The HR after C-OPV was 0.69 (95% confidence interval: 0.52-0.90). National campaigns providing vitamin A or measles vaccine did not have similar effects. Each additional dose of C-OPV was associated with a reduction in the mortality rate by 6% (-2 to 13%). The number needed to treat with C-OPV to save one life between 0 and 35 months of age was 88 (81-96).

INTERPRETATION

This is the fourth study to show that C-OPV has beneficial non-specific effects on child survival. All studies have shown a beneficial effect of C-OPV on child health. Stopping OPV as planned after polio eradication without any mitigation plan could have detrimental effects for overall child health in low-income countries.

FUNDING

The Chakaria HDSS was funded by international sponsors. No sponsor had any influence on the preparation of the article.

Out-of-Sequence Vaccinations With Measles Vaccine and Diphtheria-Tetanus-Pertussis Vaccine: A Reanalysis of Demographic Surveillance Data From Rural Bangladesh

BACKGROUND

Due to delays in vaccinations, diphtheria-tetanus-whole-cell-pertussis (DTP) is often given with or after measles vaccine (MV)-out of sequence. We reanalyzed data from Matlab, Bangladesh, to examine how administration of MV and DTP out-of-sequence was associated with child survival.

METHODS

In sum, 36 650 children born between 1986 and 1999 were followed with registration of vaccinations and survival. Controlling for background factors using Cox proportional hazards models, survival was analyzed between 9 and 24 months of age. We measured the mortality rate ratio (MRR) to compare vaccination groups. Oral polio vaccine (OPV) campaigns, which started in 1995, reduced the mortality rate and reduced the difference between vaccination groups. In the main analysis, we therefore censored for OPV campaigns; there were 151 nonaccident deaths before the OPV campaigns.

RESULTS

Compared with MV administered alone (MV-only), DTP administered with or after MV had MRR 2.20 (1.31-3.70), and DTP-only had MRR 1.78 (1.01-3.11). Compared with MV-only, DTP administered with MV had a female-male MRR 0.56 (0.13-2.38), significantly different to DTP administered after MV, which had MRR 14.83 (1.88-117.1), test of interaction P = .011. Compared with having DTP (no MV) as most recent vaccination, MV-only had a nonaccident MRR of 0.56 (0.32-0.99).

CONCLUSION

The negative effects of non-live DTP with or after live MV are not explained merely by selection bias. These observations support a live-vaccine-last policy where DTP should not be given with or after MV.

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.

Maternal Priming: Bacillus Calmette-Guérin (BCG) Vaccine Scarring in Mothers Enhances the Survival of Their Child With a BCG Vaccine Scar

BACKGROUND AND HYPOTHESIS

Maternal priming might enhance the beneficial nonspecific effects (NSEs) of live measles vaccination (MV). Children with a bacillus Calmette-Guérin (BCG) vaccine scar have a lower mortality rate than those without a scar that is not explained by protection against tuberculosis. We examined the hypothesis that BCG scarring would have a stronger effect on a child if the mother also had a BCG scar.

METHODS

In a randomized controlled trial (RCT) of early MV in children aged 4.5 months, the BCG-scar status of the children and their mother were registered at enrollment at 4.5 months of age. The children were followed up until they were 36 months of age. Using a Cox proportional hazards model, we compared mortality rate ratios according to maternal and child BCG-scar status after adjusting for where the BCG vaccine was given (the national hospital or elsewhere). We censored for other interventions that have immunomodulating effects on child survival, including neonatal vitamin A supplementation and early MV.

RESULTS

A total of 2213 children had not received neonatal vitamin A supplementation and early MV; 83% of these children and 44% of the mothers had a BCG scar. Children whose mother had a BCG scar were not more likely to have a BCG scar than those whose mother did not have a BCG scar (risk ratio, 1.01 [95% confidence interval (CI), 0.98-1.05]). Among the children, having a BCG scar was associated with a 41% (95% CI, 5%-64%) lower mortality between the ages of 4.5 and 36 months. The reduction in mortality was 66% (95% CI, 33%-83%) if the mother also had a BCG scar but only 8% (95% CI, -83% to 53%) if the mother had no BCG scar (test of interaction, P = .04).

CONCLUSIONS

Maternal BCG priming might be important for the effect of BCG vaccination on child survival. Ensuring better BCG vaccine scarring among mothers and children could have a considerable effect on child mortality levels.

Research protocol of two concurrent cluster-randomized trials: Real-life Effect of a CAMPaign with Measles Vaccination (RECAMP-MV) and Real-life Effect of a CAMPaign with Oral Polio Vaccination (RECAMP-OPV) on mortality and morbidity among children in rural Guinea-Bissau

BACKGROUND

Measles and oral polio vaccinations may reduce child mortality to an extent that cannot be explained by prevention of measles and polio infections; these vaccines seem to have beneficial non-specific effects. In the last decades, billions of children worldwide have received measles vaccine (MV) and oral polio vaccine (OPV) through campaigns. Meanwhile the under-five child mortality has declined. Past MV and OPV campaigns may have contributed to this decline, even in the absence of measles and polio infections. However, cessation of these campaigns, once their targeted infections are eradicated, may reverse the decline in the under-five child mortality. No randomized trial has assessed the real-life effect of either campaign on child mortality and morbidity. We present the research protocol of two concurrent trials: RECAMP-MV and RECAMP-OPV.

METHODS

Both trials are cluster-randomized trials among children registered in Bandim Health Project's rural health and demographic surveillance system throughout Guinea-Bissau. RECAMP-MV is conducted among children aged 9-59 months and RECAMP-OPV is conducted among children aged 0-8 months. We randomized 222 geographical clusters to intervention or control clusters. In intervention clusters, children are offered MV or OPV (according to age at enrolment) and a health check-up. In control clusters, children are offered only a health check-up. Enrolments began in November 2016 (RECAMP-MV) and March 2017 (RECAMP-OPV). We plan 18,000 enrolments for RECAMP-MV with an average follow-up period of 18 months and 10,000 enrolments for RECAMP-OPV with an average follow-up period of 10 months. Data collection is ongoing. The primary outcome in both trials is non-accidental death or non-accidental first non-fatal hospitalization with overnight stay (composite outcome). Secondary outcomes are: non-accidental death, repeated non-fatal hospitalizations with overnight stay, cause-specific primary outcome, outpatient visit, and illness. We obtained ethical approval from Guinea-Bissau and consultative approval from Denmark.

DISCUSSION

Cluster randomization and minimum risk of loss to follow-up are strengths, and no placebo a limitation. Our trials challenge the understanding that MV and OPV only prevent measles and polio, and that once both infections are eradicated, campaigns with MV and OPV can be phased out without negative implications on child health and survival.

TRIAL REGISTRATION

NCT03460002.

Stopping live vaccines after disease eradication may increase mortality

Several live vaccines may have beneficial non-specific effects (NSEs) reducing mortality more than can be explained by the prevention of the target infection, a phenomenon which has been linked to innate immune training. Most randomised controlled trials (RCTs) of oral polio vaccine (OPV) and measles vaccine (MV) have shown a large reduction in mortality that must have been at least partly nonspecific because it was much larger than the reduction explained by prevention of the target disease. Hence, stopping a live vaccine after disease-eradication could have negative health effects if the potential beneficial NSEs are not considered. We reviewed one eradicated disease, smallpox, and two infections likely to be eradicated in coming decades, polio and measles. No study was made of unintended effects of stopping smallpox vaccination when it happened in 1980. We have subsequently documented in both Guinea-Bissau and Denmark that smallpox-vaccinated individuals continued to have a survival advantage long after smallpox had been eradicated. The few studies which have examined the effect of OPV on survival all suggest strong beneficial NSEs; in RCTs, OPV compared with inactivated polio vaccine (IPV) has been associated with non-specific reductions in morbidity. RCTs, natural experiments and observational studies have found strong beneficial NSEs for MV. Hence, the imminent eradication of polio and the planned stop of OPV in 2024 and the subsequent eradication of measles infection and the possible stop to live MV could have negative effects for child survival. Before live vaccines are phased out, potential unintended effects of stopping these vaccines should be thoroughly studied.

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

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

Effect of sex on vaccination outcomes: important but frequently overlooked

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

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.

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

Background

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

Methods

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

Results

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

Conclusion

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

National Immunization Campaigns with Oral Polio Vaccine Reduce All-Cause Mortality: A Natural Experiment within Seven Randomized Trials

BACKGROUND

A recent WHO review concluded that live BCG and measles vaccine (MV) may have beneficial non-specific effects (NSEs) reducing mortality from non-targeted diseases. NSEs of oral polio vaccine (OPV) were not examined. If OPV vaccination campaigns reduce the mortality rate, it would suggest beneficial NSEs.

SETTING

Between 2002 and 2014, Guinea-Bissau had 15 general OPV campaigns and other campaigns with OPV plus vitamin A supplementation (VAS), VAS-only, MV, and H1N1 vaccine. In this period, we conducted seven randomized controlled trials (RCTs) with mortality as main outcome.

METHODS

Within these RCTs, we assessed whether the mortality rate was lower after-campaign than before-campaign. We used Cox models with age as underlying time and further adjusted for low birth-weight, season and time trend in mortality. We calculated the adjusted mortality rate ratio (MRR) for after-campaign vs before-campaign.

RESULTS

The mortality rate was lower after OPV-only campaigns than before, the MRR being 0.81 (95% CI = 0.68-0.95). With each additional dose of campaign-OPV the mortality rate declined further (MRR = 0.87 (95% CI: 0.79-0.96) per dose) (test for trend, p = 0.005). No other type of campaign had similar beneficial effects. Depending on initial age and with follow-up to 3 years of age, the number needed to treat with campaign-OPV-only to save one life was between 68 and 230 children.

CONCLUSION

Bissau had no case of polio infection so the results suggest that campaign-OPV has beneficial NSEs. Discontinuation of OPV-campaigns in low-income countries may affect general child mortality levels negatively.

The nonspecific face of adaptive immunity

Memory T cells generated by infection or immunization persist in the organism and mediate specific protection upon rechallenge with microbial pathogens expressing the same molecular structures. However, multiple lines of evidence indicate that previously encountered or persisting pathogens influence the immune response to unrelated pathogens. We describe the acquisition of non-antigen specific memory features by both innate and adaptive immune cells explaining these phenomena. We also focus on the different mechanisms (homeostatic or inflammatory cytokine-driven) that lead to acquisition of memory phenotype and functions by antigen-inexperienced T lymphocytes. We discuss the implications of these new concepts for host defense, auto-immunity and vaccination strategies.

Expected and Unexpected Effects of Vaccination

Vaccination is widely considered to be one of the greatest medical achievements of civilization and one of the top major breakthroughs of humanity.