SMV delivery

The challenge

The development of malaria vaccines was a major step forward in the battle against malaria. However, they do not completely eliminate the risk of malaria, and they are recommended to be used alongside other control measures, such as insecticide-impregnated bed nets and seasonal malaria chemoprevention (SMC). In addition, the malaria vaccine schedule is complex, requiring at least 4 doses in the first 2 years of life.

Malaria vaccination generally follows an age-based schedule, with a primary series of three doses given at monthly intervals starting at around 5 months of age. However, protection declines over time after vaccination, so at least one booster dose of vaccine is subsequently given to help maintain protection. This is generally also given according to an age-based schedule (~1 year after the priming doses). However, in areas where malaria cases typically occur only during certain months of the year, such as the Sahel, it has been suggested that a seasonal schedule, i.e. giving a booster dose just before the malaria season (regardless of the precise interval since their priming doses) would better protect young children during these crucial months, but this remains to be proven. Moreover, vaccine coverage is generally lower for later doses. 

Discussions with policymakers suggest that the primary series of three doses is best delivered through countries’ standard childhood immunisation programme, but there is less consensus on how booster doses should be delivered: through these same national childhood vaccination clinics, or through dedicated community mass campaigns.

The project

The SMV delivery project aims to compare the impact of three different malaria vaccine booster delivery strategies, following a standard initial three-dose primary series:

• Strategy 1: Age-based delivery of a booster dose through national childhood immunisation programme clinics.
• Strategy 2: Seasonal delivery of a booster dose through national childhood immunisation programme clinics.
• Strategy 3: Seasonal delivery of a booster dose through a dedicated community mass campaign.

To compare these approaches, two trials are underway, one in Guinea and one in Mali. Two matched areas have been identified in each country, and each will adopt a different strategy:

• Guinea: Age-based booster (strategy 1) versus seasonal booster (strategy 2).
• Mali: (Seasonal) booster delivered through childhood immunisation programme clinics (strategy 2) versus (seasonal) booster delivered through a community mass campaign (strategy 3).

The trials assess the effects of the two strategies on booster-dose coverage and the number of malaria cases. In addition, aspects such as cost-effectiveness, barriers to implementation, and caregiver and health worker attitudes toward different strategies are investigated, as is the impact of different booster-dose delivery strategies on vaccine-induced immune responses. 

Impact

The SMV delivery project will generate evidence directly relevant to health policymakers. It will:

• Provide comparative evidence on the vaccine booster coverage and malaria control achieved by the different delivery strategies.
• Generate insights into barriers and facilitators that could affect the implementation of each strategy.
• Provide an indication of the cost implications of the different strategies.

The SMV delivery project is designed to provide policymakers with the evidence they need to introduce the optimal strategy to minimise malaria cases among young children, thereby further reducing deaths from this disease.