Photo: WHO / Francis Kokoroko
Representatives from the National Malaria Programmes (NMPs) and Expanded Programmes of Immunization (EPIs) from 13 African countries in West and Central Africa participated in a recent workshop to consider implementation strategies for delivering the RTS,S/AS01 (RTS,S) malaria vaccine in settings with seasonal transmission. This included discussions on the need for implementation research to optimize the roll-out of the vaccine. The workshop was co-hosted by the OPT-SMC initiative and TDR through the Access and Delivery Partnership (ADP), with technical input from Gavi, the WHO Malaria Vaccines team, the WHO Regional Office for Africa, PATH and other stakeholders.
In October 2021, WHO recommended the RTS,S malaria vaccine for use to prevent malaria among children living in areas with moderate to high malaria transmission, informed by available clinical evidence and findings from the pilot implementation of the malaria vaccine in routine immunization programmes in Ghana, Kenya and Malawi. Gavi, the Vaccine Alliance, approved funding to support the roll-out of the vaccine, and country applications are currently being considered at a time when demand is high and RTS,S vaccine supply is limited.
Nearly 1.5 million children have been reached with the malaria vaccine in Ghana, Kenya and Malawi since the launch of the pilot programme in 2019. The experiences and lessons learned in the three pilot countries are invaluable and can help inform planning for vaccine roll-out in other countries. Some questions on implementation remain regarding the introduction of this (and potentially other) new malaria vaccines across Africa. In-depth exploration is required to inform the implementation of the RTS,S vaccine particularly in countries with low or moderate EPI vaccine coverage and/or highly seasonal malaria transmission, where greater challenges are expected to be encountered. Vaccine delivery may need to be adapted to optimize malaria control strategies to maximize the reduction of child morbidity and mortality in such settings.
The workshop, held in Dakar, Senegal and virtually, in January 2023, aimed to address questions about delivering the RTS,S vaccine in the context of seasonal malaria transmission and variability in routine childhood immunization coverage. During the workshop, current evidence on RTS,S efficacy and impact was reviewed. As the first pilot countries to introduce RTS,S through routine child vaccination services, Ghana, Kenya and Malawi shared their experiences to date.
Participants in this workshop included representatives from the National Malaria Programmes (NMPs) and Expanded Programmes of Immunization (EPIs) from 13 African countries that currently implement seasonal malaria chemoprevention (SMC) in West and Central Africa. SMC is a highly effective intervention to reduce the burden of malaria in high endemicity settings. It is delivered just before and during the height of malaria transmission, generally coinciding with the rains.
RTS,S/AS01 workshop participants in Dakar, Senegal, January 2023
Credit: Université de Thiès
Joint efforts between NMPs and EPI teams have been conducive in the three pilot countries. RTS,S efficacy in highly seasonal settings is significant; a phase 3 trial (2017-2020) of the vaccine provided just prior to the peak malaria season in areas of highly seasonal malaria found vaccine efficacy similar to efficacy of SMC, which is shown to prevent around 75% of malaria cases. However, duration of protection wanes over time, thus, timing of doses in relation to the transmission season is an important consideration. This information exchange has allowed considerations for the roll-out of the malaria vaccine in SMC implementing countries that are currently considering the introduction of the RTS,S malaria vaccine. Rich discussions ensued regarding implementation strategies and modes of delivery in countries with seasonal transmission and low or moderate EPI coverage particularly for children in the second year of life. Regulatory and supply management issues for introduction of RTS,S into the health systems of these countries were also covered during the workshop.
Implementation research to investigate vaccine delivery models
“The combination of effective strategies such as seasonal malaria chemoprevention, long-lasting insecticidal nets, plus the new RTS,S vaccine implemented at high coverage could reduce the malaria burden by up to 92%,” says Professor Jean-Louis Ndiaye from the Université de Thiès in Senegal, citing findings from previous studies.
The most optimal RTS,S delivery strategy in regions with seasonal malaria may require a hybrid delivery model with administration of doses 1-3 at monthly intervals from 5 months of age through routine EPI, and delivery of doses 4 and 5 annually (potentially through a campaign approach) just prior to the malaria season, for example in conjunction with SMC. This approach has not been implemented in public health programmes to date and might be associated with practical challenges. Yet, it is possible that this model could strike the balance between maximum vaccine efficacy, cost-effectiveness and feasibility for roll-out of the RTS,S vaccine.
There is a great need for exploration of this approach through implementation research, especially regarding mode of delivery and timing for the fourth dose, which is required for maximum protection.
The WHO Malaria Vaccines team and Gavi plan to facilitate the development of a comprehensive and vetted learning agenda in consultation with researchers and stakeholders on the ground across the African continent, to capture general and more specific implementation priorities generated in the Global South.
They urged countries that are beginning to introduce RTS,S to document and share lessons learned from seasonal vaccination strategies, especially regarding operational feasibility and vaccine efficacy and safety. Continued information exchange between countries planning to introduce RTS,S should be facilitated and are indeed planned under the umbrella of the ADP partnership.
For more details on the workshop and additional information, please visit: Workshop: Implementation strategies for delivering RTS,S in countries with seasonal transmission
For more information, please contact:
Dr Corinne Merle (TDR)
Dr Branwen Hennig (TDR)
This article was originally published in https://tdr.who.int