A licensed malaria vaccine would provide a valuable new tool for malaria control and elimination efforts.
Several candidate vaccines targeting different stages ofthe malaria parasite’s lifecycle are currently under
development, with one candidate, RTS,S/AS01 for the prevention of Plasmodium falciparum infection,
having recently completed Phase III trials. Predicting the public health impact of a candidate malaria
vaccine requires using clinical trial data to estimate the vaccine’s efficacy profile—the initial efficacy
following vaccination and the pattern of waning of efficacy over time. With an estimated vaccine efficacy
profile, the effects of vaccination on malaria transmission can be simulated with the aid of mathematical
models.
Here, we provide an overview of methods for estimating the vaccine efficacy profiles of pre-erythrocytic
vaccines and transmission-blocking vaccines from clinicaltrial data. In the case of RTS,S/AS01, model estimates
from Phase II clinical trial data indicate a bi-phasic exponential profile of efficacy against infection,
with efficacy waning rapidly in the first 6 months after vaccination followed by a slower rate of waning
over the next 4 years. Transmission-blocking vaccines have yet to be tested in large-scale Phase II or
Phase III clinical trials so we review ongoing work investigating how a clinical trial might be designed to
ensure that vaccine efficacy can be estimated with sufficient statistical power. Finally, we demonstrate
how parameters estimated from clinical trials can be used to predict the impact of vaccination campaigns
on malaria using a mathematical model of malaria transmission