In 2021 alone, 25 million children globally did not receive the first dose of the diphtheria-tetanus-pertussis-
containing vaccine (DTP1). The vast majority of these - live in low-income and middle-
income countries. In addition, many children received their first dose of the measles-containing vaccine
(MCV1) much later than scheduled, thus, are at significant risk of becoming infected before they are eventually
vaccinated and may contribute to suboptimal herd immunity. In The Gambia, there is a recent upsurge of
measles, with a 6-fold increase in cases as of mid-2022 compared to 2020 figures despite achieving a
minimum MCV1coverage of 90% over the last decade. Recent data suggest that a large proportion of
vaccinations are delayed or not delivered in an age-appropriate manner, according to the national vaccination
windows. In addition, untimely MCV1 and zero-dose are thought to co-exist and clustered in certain remote
communities and may contribute to suboptimal herd immunity. The PI, Dr Oghenebrume Wariri will apply novel
spatiotemporal modelling approaches to map the subpopulation with untimely measles vaccination and zero-
dose at fine-spatial scale and examine potential links with suboptimal herd immunity and risk of measles
outbreaks. He will also examine how geographic accessibility shapes the uptake and delivery of routine
vaccination in The Gambia. The project will leverage longitudinal cohort data from Health and Demographic
Surveillance Systems in The Gambia, and bio-banked serological samples covering rural populations in the
Kiang West District of The Gambia. There are four specific aims for this K43 award: 1) to determine the
spatiotemporal pattern of untimely MCV1 and zero-dose children at high-spatial resolution in The Gambia; 2) to
determine if there is a spatiotemporal relationship between cluster location of untimely MCV1 and measles
population immunity in The Gambia; 3) To investigate the contribution of geographic accessibility (between
households and vaccination posts; and between fixed and outreach vaccination posts) to zero-dose prevalence
and delayed MCV1; 4) to model geographic access to routine vaccination services to understand the utility of
the current vaccine delivery channels and potentially identify optimal locations of vaccination clinics and posts.
This K43 Award will equip Dr Wariri with novel skills and competencies in geospatial and infectious disease
modelling, manuscript and grant writing. Dr Wariri will be working with a multi-disciplinary mentoring committee
comprising internationally-recognised African, UK, and US-based experts in vaccinology, population immunity
and infectious diseases modelling, and geospatial modelling. The proposed research, in combination with a
structured mentoring and training plan that includes didactic courses and workshops, is designed to facilitate
Dr. -term goal of developing an independently funded infectious diseases and spatial epidemiology
research program focussed on vaccination in Africa, consistent with the mission of the Fogarty International
Centre.
