A field trial of a new malaria vaccine that uses viruses carrying malaria antigen to stimulate the immune system to resist the pathogen has reported promising early results.
The international consortium conducting the Kenyan trial reports its findings in the journal Science Translational Medicine.
The vaccine – developed by the Jenner Institute at Oxford University in the UK – was found to be 67% effective at protecting against infection by Plasmodium falciparum, one of the parasites that causes malaria.
Malaria is a disease that results from the bite of a female mosquito carrying a Plasmodium parasite.
A safe and effective malaria vaccine would do much to reduce the huge social and economic burden of a disease that kills hundreds of thousands of people a year – most of them young children in sub-Saharan Africa.
Following decades of research, this is now the second malaria vaccine to show promise in recent trials. Another vaccine – recently tested in more advanced trials – was shown to be partially effective in protecting children for up to 4 years.
The new vaccine is based on two virus “vectors” encoded with a key protein or antigen for Plasmodium falciparum that triggers the immune system to produce T-cells to protect against malaria.
The vectors are disabled viruses designed to carry the antigen into the liver and trigger the production of T-cells that can recognize and fight the parasite should it enter the bloodstream of the vaccinated person.
The two viruses are a recombinant chimpanzee adenovirus 63 (ChAd63) and the modified vaccinia Ankara (MVA). They both carry the code for the malaria antigen ME-TRAP (multiple epitope string and thrombospondin-related adhesion protein).
The researchers conducted the field trial of the “T cell-inducing vaccination strategy” among healthy, male, adult volunteers living in a malaria-endemic area in Kilifi County, Kenya.
The 121 volunteers were randomly assigned to receive either the new vaccine or a rabies vaccine (as a control). At the start of the trial, they all received antimalaria drugs to clear any parasites from their blood.
During 8 weeks of follow-up, the researchers tested blood samples from the volunteers to identify new infections with P. falciparum.
The results showed that T-cell inducing vaccination reduced the risk of infection with P. falciparum by 67%.
One of the researchers, Adrian Hill, director of the Jenner Institute and professor of human genetics at Oxford, says:
“This is an exciting and very positive result with this new type of malaria vaccine that targets the parasite in the liver by inducing protective T cell responses. Such high efficacy in this first field trial is encouraging for further testing in children and infants who most need a malaria vaccine.”
The promising result means the researchers can move onto larger field trials in several populations.
Philip Bejon, professor of tropical medicine at Oxford and Executive Director of the KEMRI – Wellcome Trust Research Programme, in Kilifi, Kenya, where the trial took place, says the result clearly shows “the potential of these new viral vectored vaccines and identifies a rapid new means of demonstrating vaccine efficacy against infection in field trials.”
The Malaria Vectored Vaccines Consortium (MVVC), that funded and ran the trial, is a 5-year project that aims to bring together resources and networks to design and carry out East and West African trials of safe and affordable viral-vectored malaria vaccines.
Meanwhile, Medical News Today has learned about a major challenge facing global efforts to eradicate malaria – the advance of drug-resistant malaria that is moving at an alarming pace across Asia.
In a paper published online in The Lancet Infectious Diseases in February 2015, scientists reported how they found evidence of parasite resistance to the frontline drug artemisinin in samples collected in and around Myanmar. Should the resistant strain spread into neighboring India, it will pose a serious threat to the global control and eradication of malaria, they warn.