Comparison of school based and supplemental vaccination strategies in the delivery of vaccines to 5-19 year olds in Africa - a systematic review

Scaling-up high-impact micronutrient supplementation interventions to improve adolescents' nutrition and health in Burkina Faso and Tanzania: protocol for a cluster-randomised controlled trial

INTRODUCTION

Adolescence is a critical time for growth and development, but this age group is often neglected in research and development of nutrition interventions. Despite recommendations from the WHO to provide nutrient supplements to adolescents, evidence remains scarce on the most effective supplementation strategy. This study aims to compare weekly iron and folic acid (IFA) supplementation with daily multiple micronutrient supplements (MMSs) in prevention of anaemia and improvement of school outcomes among adolescents in Burkina Faso and Tanzania.

METHODS AND ANALYSIS

A three-arm cluster-randomised, school-based supplementation trial will be conducted among 84 schools (42 schools per site) and roughly 4500 students aged 10-17. Schools will be matched on three characteristics: number of students, school ranking profile, distance to main road (Tanzania) or distance to city council (Burkina Faso). Each school will be randomised to receive either weekly IFA, daily MMSs or serve as a control. Supplements will be delivered to students by teachers, who will provide monitoring data to the study team. Baseline and endline surveys will be conducted prior to and after each supplementation cycle (12 weeks in Burkina Faso; 1 year in Tanzania) to assess haemoglobin, anthropometry and sociodemographic variables. The primary outcome of haemoglobin will be analysed continuously using linear regression, and anaemia status will be analysed using logistic or multinomial regression, depending on categorisation level of the outcome. Secondary analyses of school performance indicators will also be conducted with either logistic or linear regression.

ETHICS AND DISSEMINATION

This protocol has been approved by the Institutional Review Board of the Harvard TH Chan School of Public Health (IRB20-1108) and the Research Ethics Committees for the Ministries of Health in Tanzania (Zanzibar) and Burkina Faso. Results will be disseminated during meetings with the Ministries of Health and the participating communities as well as through peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT04657640; NCT05104554.

Policy implications of the potential use of a novel vaccine to prevent infection with Schistosoma mansoni with or without mass drug administration

Schistosomiasis is one of the most important neglected tropical diseases (NTDs) affecting millions of people in 79 different countries. The World Health Organization (WHO) has specified two control goals to be achieved by 2020 and 2025 - morbidity control and elimination as a public health problem (EPHP). Mass drug administration (MDA) is the main method for schistosomiasis control but it has sometimes proved difficult to both secure adequate supplies of the most efficacious drug praziquantel to treat the millions infected either annually or biannually, and to achieve high treatment coverage in targeted communities in regions of endemic infection. The development of alternative control methods remains a priority.

In this paper, using stochastic individual-based models, we analyze whether the addition of a novel vaccine alone or in combination with drug treatment, is a more effective control strategy, in terms of achieving the WHO goals, as well as the time and costs to achieve these goals when compared to MDA alone. The key objective of our analyses is to help facilitate decision making for moving a promising candidate vaccine through the phase I, II and III trials in humans to a final product for use in resource poor settings.

We find that in low to moderate transmission settings, both vaccination and MDA are highly likely to achieve the WHO goals within 15 years and are likely to be cost-effective. In high transmission settings, MDA alone is unable to achieve the goals, whereas vaccination is able to achieve both goals in combination with MDA. In these settings Vaccination is cost-effective, even for short duration vaccines, so long as vaccination costs up to US$7.60 per full course of vaccination. The public health value of the vaccine depends on the duration of vaccine protection, the baseline prevalence prior to vaccination and the WHO goal.

Modelling the impact of a Schistosoma mansoni vaccine and mass drug administration to achieve morbidity control and transmission elimination

Mass drug administration (MDA) is, and has been, the principal method for the control of the schistosome helminths. Using MDA only is unlikely to eliminate the infection in areas of high transmission and the implementation of other measures such as reduced water contact improved hygiene and sanitation are required. Ideally a vaccine is needed to ensure long term benefits and eliminate the need for repeated drug treatment since infection does not seem to induce lasting protective immunity. Currently, a candidate vaccine is under trial in a baboon animal model, and very encouraging results have been reported. In this paper, we develop an individual-based stochastic model to evaluate the effect of a vaccine with similar properties in humans to those recorded in baboons in achieving the World Health Organization (WHO) goals of morbidity control and elimination as a public health problem in populations living in a variety of transmission settings. MDA and vaccination assuming different durations of protection and coverage levels, alone or in combination, are examined as treatment strategies to reach the WHO goals of the elimination of morbidity and mortality in the coming decade. We find that the efficacy of a vaccine as an adjunct or main control tool will depend critically on a number of factors including the average duration of protection it provides, vaccine efficacy and the baseline prevalence prior to immunization. In low prevalence settings, simulations suggest that the WHO goals can be achieved for all treatment strategies. In moderate prevalence settings, a vaccine that provides 5 years of protection, can achieve both goals within 15 years of treatment. In high prevalence settings, by vaccinating at age 1, 6 and 11 we can achieve the morbidity control with a probability of nearly 0.89 but we cannot achieve elimination as a public health problem goal. A combined vaccination and MDA treatment plan has the greatest chance of achieving the WHO goals in the shorter term.

Nearly 258 million people are infected worldwide by schistosome parasites. The World Health Organization (WHO) has set control guidelines to combat the morbidity and mortality induced by infection, defined by reaching ≤5% and ≤1% prevalence of heavy-intensity infections in school-aged children (SAC), respectively. Mass drug administration (MDA) is the major route for morbidity control and elimination. However, MDA does not provide long-term protection against schistosome parasites and frequent drug administration is therefore required to control morbidity. Infection does not induce lasting acquired immunity to reinfection. Drug resistance is another issue with MDA which, if it arises, could possibly make drug treatment ineffective over time as drug-resistant genes in the parasite population increase in frequency. A vaccine is ideally needed to both reduce the possibility of reinfection and to achieve transmission elimination within a feasible time frame. Based on the recent results obtained for a new candidate vaccine in the baboon animal model, we employ an individual-based stochastic model to assess the impact of a vaccine with an efficacy of 100% when applied in endemic regions with different intensities of transmission. Simulations suggest that the probability of achieving morbidity control and elimination as a public health problem depends on the duration of protection provided by vaccination, the age categories of the human host population vaccinated, and the coverage levels achieved. In order to achieve elimination as a public health problem, model simulations suggest that combining vaccination (with 5 years of protection) with MDA (treating 75% of school-aged children, 5–14 years of age) is the best option, particularly in high transmission settings.

Comparison of school based and supplemental vaccination strategies in the delivery of vaccines to 5-19 year olds in Africa - a systematic review

Background: Some vaccine preventable diseases (VPDs) still remain a public health burden in many African countries. The occurrence of VPDs in all age groups has led to the realization of the need to extend routine immunisation services to school age children, adolescents and adults. Supplemental immunisation activities (SIAs) and school based vaccinations (SBVs) are common strategies used to complement the expanded programme on immunisation (EPI). This review aimed to assess the effectiveness of SIAs compared to SBVs in the administration of vaccines to 5-19 year olds in Africa.

Methods: Systematic review methods were used to address our study aim. Several electronic databases were searched up to March 30, 2017 for primary studies investigating the delivery of vaccines via SIAs or SBVs to 5-19 year olds. This search was complemented by browsing reference lists of potential studies obtained from search outputs. Outcomes considered for inclusion were: vaccination coverage, costs of the strategy or its effect on routine immunisation services.

Results: Out of the 4938 studies identified, 31 studies met the review inclusion criteria. Both SIAs and SBVs showed high vaccination coverage. However, the SIAs reported higher coverage than SBVs: 91% (95% CI: 84%, 98%) versus 75% (95% CI: 67%, 83%). In most settings, SBVs were reported to be more expensive than SIAs. The SIAs were found to negatively affect routine immunisation services.

Conclusions: Both SIAs and SBVs are routinely used to complement the EPI in the delivery of vaccines in Africa. In settings where school enrolment is suboptimal, as is the case in many African countries, our results show SIAs may be more effective in reaching school age children and adolescents than SBVs. Our results re-iterate the importance of evaluating systematic evidence to best inform African authorities on the optimal vaccine delivery strategies targeting school age children and adolescents.