Changing dosing schedule of a malaria vaccine candidate can improve its efficacy to about 87 per cent, compared with 63 per cent using the current standard regimen, a new study has found. The study was conducted at the Walter Reed Army Institute of Research (WRAIR) in the US in 30 malaria-naive adults, using the controlled human malaria infection model (CHMI), also referred to as the malaria challenge model.
Malaria continues to have a devastating global impact, infecting more than 200 million people annually and killing an estimated 438,000- most of them young children – in 2015. The RTS,S/AS01 malaria vaccine candidate – developed in the early 1980s – is the first vaccine to successfully complete a pivotal large-scale phase 3 trial in Africa.
The paediatric RTS,S/AS01 vaccine candidate has been positively reviewed by the European Medicines Agency (EMA) and recommended for pilot implementation in sub-Saharan Africa by the World Health Organisation (WHO) to determine its potential real-world application.
This regimen has been shown to reduce cases of malaria by about half over 18 months of follow-up in children 5 to 17 months at first vaccination, and the administration of a fourth dose at 18 months results in an about 40 per cent reduction in cases over four years of follow-up. Its ability to protect against malaria waned over time.
In light of the partial efficacy profile of RTS,S/AS01, scientists have continued investigating a variety of strategies to improve the absolute level of the vaccine’s efficacy. In the new study, researchers sought to determine if a novel immunisation schedule, specifically delaying RTS,S/AS01 administration and reducing dosage of the third vaccination, as well as any following booster dose, would significantly increase the candidate vaccine’s ability to protect against infection.