Infectious Diseases

Biography

Biography: Peter F. Billingsley

Abstract

Cases and deaths caused by malaria worldwide increased in 2016. Prevalence of Plasmodium falciparum (Pf) by RDT was ~11% in 2-14-year olds on Bioko Island, Equatorial Guinea (EG) in 2017 compared to ~45% in 2004. Between 2004 and 2017, a national and international team supported by a technical advisory group instituted intense malaria control measures funded by one of the largest per capita investments in malaria control in the world. Consistent with prevalence reduction, malaria related mortality was reduced by ~85% and the EIR and basic case reproduction number (R₀) by >90%. However, the prevalence as measured by RDT has remained stable recently (14% and 11% in 2012 and 2016), and qPCR studies in EG indicate prevalence is 3-fold higher. This situation is common in Africa. New tools are needed to move toward an R₀ <1 and elimination. R₀ has two components, vectorial capacity of mosquitoes and the chance an individual bitten by an infected mosquito will transmit: the majority of investment in malaria control is aimed at reducing vectorial capacity. Case management and other treatment strategies reduce the chance an exposed individual will transmit in the short term. A vaccine with significant efficacy against infection could have an enormous additional impact on the probability an exposed individual can transmit, directly protecting many and indirectly protecting many more through herd immunity if administered to an entire community. PfSPZ Vaccine induced sterile protection for 6 months against intense Pf transmission in 3 clinical trials in Mali and Burkina Faso. Protection by time to event and proportional analyses reached 52% and 38% respectively, opening the possibility of mass vaccination programs to regionally eliminate Pf. The results of clinical trials including >5,000 injections to >2,000 subjects of PfSPZ products and plans for Phase 3 and 4 trials and elimination campaigns will be presented.