The overall goal of this study is to assess the impact of RTS,S (malaria) vaccination and PBO nets on malaria infection and transmission, independently and how they interact when they are introduced together.

The specific objectives for the study are as follows:

1. To estimate the impact of PBO nets and RTS,S vaccine on Plasmodium infection prevalence and transmission, independently and how they interact when they are introduced together in Malawi (Phase 1).
2. To assess the feasibility of evaluating the impact of RTS,S vaccine and PBO nets independently in a larger scale future study.

Introduction: The decline in malaria incidence has stalled globally and incidence is increasing in some high transmission settings of sub-Saharan Africa, including Malawi. The situation is worsening despite the scale-up of previously effective interventions, raising concerns that the impact of current malaria control and prevention strategies maybe compromised.

Problem: There is an urgent need for innovative approaches to malaria control and Malawi is currently positioned to assess two of the most promising new interventions. The Malawi Ministry of Health (MOH) is launching large scale projects to evaluate a new formulation of insecticide-treated bed nets with a chemical synergist, piperonyl butoxide (PBO), designed to enhance the insecticidal effect of pyrethroids and the new malaria vaccine RTS,S (RTS,S). In an effort to gain the most information from these, interventions Malawi's National Malaria Control Programme (NMCP) have invited the Malawi International Center for Excellence in Malaria Research (ICEMR) to evaluate the effectiveness of the two interventions (alone and in combination) on malaria prevalence and transmission.

Objective: In this proposed implementation study, we propose to assess the impact of PBO nets and RTS,S vaccine on Plasmodium infection prevalence and transmission.

Study type and methodology: We will enroll children in a prospective cohort study in which the follow-up will be at the 2nd, 4th, and 6th month. We are selecting two health center catchment areas: one in which both RTS,S and PBO nets are available through the government health system and one in which there is no RTS,S vaccine available and standard long-lasting insecticide-treated nets (LLINS) have been distributed through the public section. At each visit, we will collect specimens to identify malaria infection and detect gametocyte infections. We will also collect and analyze mosquitoes from 100 households in both catchment areas to provide an entomological evidence of the force of infection. Children in households that are scheduled to receive both PBO nets and RTS,S vaccine will be compared to children in households that are not scheduled to receive either of these interventions.

Inclusion Criteria:

• Children aged 7 to 18 months of age (age-eligible for at least 3 doses of RTS,S doses) OR being one of not more than two children living in the household of an enrolled age-eligible child and being >18 mos and < 10 years of age.
• Not on cotrimoxazole prophylaxis for HIV infection
• Weight >5 kg
• Permanent residence of Health Centre (HC) catchment area
• Residence within 10 km from the HC
• Written informed consent from parent/guardian for the child to participate in the study

Exclusion Criteria:

Non-residents of the catchment area and visitors to the study area will be excluded because the study requires follow-up for at least 6 months and access to interventions such as conventional, PBO nets and malaria vaccination.

Children whose age is between 7 and 18 months, which indicates they could receive at least 3 RTS,S doses, will be eligible to participate. Following informed consent from parents/guardians, up to two children who are 18 months but ≤10 years of age, from the same household as the vaccine-eligible child, will also be enrolled. Only households whose families intend to stay in the area for at least six months and whose eligible children will also be expected to use an assigned health center for child vaccinations will be eligible to participate.

Only de-identified data will be shared.