I have started my research career with the evaluation of the impact of the Gambian National insecticide-treated bed nets (ITNs) on childhood morbidity and mortality and on malaria in pregnancy. ITNs reduced mortality in children <10 years of age by 25%. It also showed that ITNs could prevent malaria in pregnancy and this resulted in a higher mean birth weight in intervention villages. This is one of the projects on which the recommendation by the World Health Organization of implementing ITNs for the prevention of malaria is based.

I also carried out, about around the same period, one of the first phase 3 malaria vaccine trials in sub-Saharan Africa, namely SPf66. Unfortunately, the vaccine was not efficacious, but the trial provided important information on how to conduct a malaria vaccine trial.

Antimalarial drug resistance and efficacy of new treatments has been for long time a major subject in my research portfolio. I have contributed assessing the magnitude of the resistance to chloroquine and sulfadoxine-pyrimethamine, both in West and Eastern Africa, and investigated how the intensity of malaria transmission influenced the spread of drug resistant parasites. I have also evaluated the safety and efficacy of artemisinin-based combination treatments in Africa and in other continents, including in high risk groups such as children <5 years old and pregnant women.  For the latter, I reported that dihydroartemisinin-piperaquine is the treatment with the highest efficacy and acceptable safety, while artemether-lumefantrine has excellent safety but lower efficacy.

I have worked extensively on malaria in pregnancy and produced data on the burden of infection and efficacy and effectiveness of control interventions. For example, I evaluated several approaches to increase the coverage of intermittent preventive treatment during pregnancy (IPTp), one of them combining IPTp with malaria screening and treatment between IPTp doses.

In the last 10 years, I investigated residual malaria transmission and factors maintaining it; and I have evaluated interventions with the potential of further reducing or interrupting residual malaria transmission. I have characterized malaria transmission across The Gambia and established the likely ‘parasite flow’ by genotyping and modelling, showing that transmission in western Gambia is partly maintained by parasites from eastern Gambia. We carried out several cluster randomized trials to evaluate the safety, efficacy and acceptability of different control interventions. For example, we recently evaluated the impact mass drug administration with ivermectin (endectocidal drug that may reduce vector survival after a blood meal) and dihydroartemisinin‐piperaquine on residual malaria transmission. The intervention decreased significantly malaria prevalence in intervention villages.  

We carried out the first Controlled Human Malaria Infection (CHMI) experiment in The Gambia and showed that individuals with serological evidence of higher malaria exposure were able to better control infection and had higher parasite growth inhibitory activity.

Finally, the MRC Unit The Gambia I am leading is fully involved in the national response to the covid-19 epidemic. Besides providing the diagnostic facilities and managing patients in our clinical services, we are starting several covid-19 related projects. We are validating a new antigen-based diagnostic test and setting up a cohort of covid-19 patients to determine their immune response over 6 months. We are about to start a treatment trial with 2 cohorts, one with mild disease patients and the other with severe disease patients.