Analysis of the potential for a malaria vaccine to reduce gaps in malaria intervention coverage

Background

The RTS,S/AS01 malaria vaccine is currently being evaluated in a cluster-randomized pilot implementation programme in three African countries. This study seeks to identify whether vaccination could reach additional children who are at risk from malaria but do not currently have access to, or use, core malaria interventions.

Methods

Using data from household surveys, the overlap between malaria intervention coverage and childhood vaccination (diphtheria-tetanus-pertussis dose 3, DTP3) uptake in 20 African countries with at least one first administrative level unit with Plasmodium falciparum parasite prevalence greater than 10% was calculated. Multilevel logistic regression was used to explore patterns of overlap by demographic and socioeconomic variables. The public health impact of delivering RTS,S/AS01 to those children who do not use an insecticide-treated net (ITN), but who received the DTP3 vaccine, was also estimated.

Results

Uptake of DTP3 was higher than malaria intervention coverage in most countries. Overall, 34% of children did not use ITNs and received DTP3, while 35% of children used ITNs and received DTP3, although this breakdown varied by country. It was estimated that there are 33 million children in these 20 countries who do not use an ITN. Of these, 23 million (70%) received the DTP3 vaccine. Vaccinating those 23 million children who receive DTP3 but do not use an ITN could avert up to an estimated 9.7 million (range 8.5–10.8 million) clinical malaria cases each year, assuming all children who receive DTP3 are administered all four RTS,S doses. An additional 10.8 million (9.5–12.0 million) cases could be averted by vaccinating those 24 million children who receive the DTP3 vaccine and use an ITN. Children who had access to or used an ITN were 9–13% more likely to reside in rural areas compared to those who had neither intervention regardless of vaccination status. Mothers’ education status was a strong predictor of intervention uptake and was positively associated with use of ITNs and vaccination uptake and negatively associated with having access to an ITN but not using it. Wealth was also a strong predictor of intervention coverage.

Conclusions

Childhood vaccination to prevent malaria has the potential to reduce inequity in access to existing malaria interventions and could substantially reduce the childhood malaria burden in sub-Saharan Africa, even in regions with lower existing DTP3 coverage.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03966-x.

New immunization strategies: adapting to global challenges

Immunization has made an enormous contribution to global health. Global vaccination coverage has dramatically improved and mortality rates among children due to vaccine-preventable diseases have been significantly reduced since the creation of the Expanded Programme of Immunization in 1974, the formation of Gavi, the Vaccine Alliance, in 2000, and the development of the Global Vaccine Action Plan in 2012. However, challenges remain and persisting inequities in vaccine uptake contribute to the continued occurrence and outbreaks of vaccine-preventable diseases. Inequalities in immunization coverage by geography, urban-rural, and socio-economic status jeopardize the achievement of global immunization goals and call for renewed immunization strategies. These should take into account emerging opportunities for building better immunization systems and services, as well as the development of new vaccine products and delivery technologies. Such strategies need to achieve equity in vaccination coverage across and within countries. This will require the participation of communities, a better understanding of vaccine acceptance and hesitancy, the expansion of vaccination across the life course, approaches to improve immunization in middle-income countries, enhanced use of data and possible financial and non-financial incentives. Vaccines also have an important role to play in comprehensive disease control, including the fight against antimicrobial resistance. Lessons learned from disease eradication and elimination efforts of polio, measles and maternal and neonatal tetanus are instrumental in further enhancing global immunization strategies in line with the revised goals and targets of the new Immunization Agenda 2030, which is currently being developed.

National immunization programmes

Immunization represents one of the most cost-effective means to improve the health and well-being of populations and contribute to sustainable development. Since the inception of the Expanded Programme on Immunization (EPI) in 1974, considerable gains have been made in improving access to vaccination in all countries. However, the full potential of vaccination is yet to be tapped.Health system weaknesses have prevented universal access to vaccination and are a limitation for sustainable use of the increasing array of new vaccines. Fortunately, solutions exist and opportunities are available to strengthen immunization systems and to implement strategies to achieve the vision of universal access to vaccines. National immunization programmes are responsible for the management of immunization at the country level and cover a range of functions from establishing evidence-based policies to financing and procurement of vaccines, vaccine management and logistics, delivery of vaccination services and collection, as well as analysis and use of immunization data. Well-functioning immunization programmes that deliver high-quality services using tailored strategies to meet the needs of different population groups can reap the health benefits of high and equitable coverage with vaccines.

The origins of the vaccine cold chain and a glimpse of the future

International efforts to eradicate smallpox in the 1960s and 1970s provided the foundation for efforts to expand immunization programmes, including work to develop immunization supply chains. The need to create a reliable system to keep vaccines cold during the lengthy journey from the manufacturer to the point of use, even in remote areas, was a crucial concern during the early days of the Expanded Programme on Immunization. The vaccine cold chain was deliberately separated from other medical distribution systems to assure timely access to and control of vaccines and injection materials. The story of the early development of the vaccine cold chain shows how a number of challenges were overcome with technological and human resource solutions. For example, the lack of methods to monitor exposure of vaccines to heat during transport and storage led to many innovations, including temperature-sensitive vaccine vial monitors and better methods to record and communicate temperatures in vaccine stores. The need for appropriate equipment to store and transport vaccines in tropical developing countries led to innovations in refrigeration equipment as well as the introduction and widespread adoption of novel high performance vaccine cold-boxes and carriers. New technologies also helped to make injection safer. Underlying this work on technologies and equipment was a major effort to develop the human resources required to manage and implement the immunization supply chain. This included creating foundational policies and a management infrastructure; providing training for managers, health workers, technicians, and others. The vaccine cold chain has contributed to one of the world's public health success stories and provides three priority lessons for future: the vaccine supply chain needs to be integrated with other public health supplies, re-designed for efficiency and effectiveness and work is needed in the longer term to eliminate the need for refrigeration in the supply chain.

Strengthening routine immunization systems to improve global vaccination coverage

BACKGROUND

Global coverage with the third dose of diphtheria-tetanus-pertussis vaccine among children under 1 year of age stagnated at ∼ 83-84% during 2008-13.

SOURCES OF DATA

Annual World Health Organization and UNICEF-derived national vaccination coverage estimates.

AREAS OF AGREEMENT

Incomplete vaccination is associated with poor socioeconomic status, lower education, non-use of maternal-child health services, living in conflict-affected areas, missed immunization opportunities and cancelled vaccination sessions.

AREAS OF CONTROVERSY

Vaccination platforms must expand to include older ages including the second year of life. Immunization programmes, including eradication and elimination initiatives such as those for polio and measles, must integrate within the broader health system.

GROWING POINTS

The Global Vaccine Action Plan (GVAP) 2011-20 is a framework for strengthening immunization systems, emphasizing country ownership, shared responsibility, equity, integration, sustainability and innovation.

AREAS TIMELY FOR DEVELOPING RESEARCH

Immunization programmes should identify, monitor and evaluate gaps and interventions within the GVAP framework.