Vaccines for malaria in the offing
Scientists are on the verge of finding vaccines for malaria after two trials of malaria vaccines developed by Sanaria, a United States of America (USA) company, proved successful.
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The vaccines are the Sanaria® PfSPZ and the Sanaria® PfSPZ-CVac.
According to a report by the science-based online Lancet Infectious Diseases and Medical Journal, journal, investigators in the first trial reported that the Sanaria® PfSPZ vaccine protected against natural infections of plasmodium falciparum.
In the second trial reported in the Nature, an international journal of science, published in the United Kingdom, investigators from the University of Tübingen, Germany, reported that all nine subjects immunised with three doses of Sanaria® PfSPZ-CVac malaria vaccine were protected against the plasmodium falciparum malaria when exposed to the disease 10 weeks after their last vaccine dose.
According to Dr Stephen Hoffman, Sanaria Founder and CEO, “It is possible that different PfSPZ-based vaccines may be required for different sub-populations and different indications such as for travellers and mass vaccination programmes.”
The first trial
The first trial was conducted in Donéguébougou, Mali in West Africa and dubbed: “Safety and efficacy of PfSPZ vaccine against plasmodium falciparum via direct venous inoculation in healthy malaria-exposed Malian adults: a randomised, double-blind trial.”
The trial was led by Dr Mahamadou Sissoko of the Malaria Research and Training Centre at the University of Science, Techniques and Technologies of Bamako, Mali, and Dr Sara Healy of the Laboratory of Malaria Immunology and Vaccinology (LMIV) of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health in Bethesda, Maryland.
In the study, five doses of PfSPZ vaccine were administered to 44 subjects while saltwater placebo was also given to 44 other subjects. Volunteers were followed for six months through the subsequent rainy season to determine the presence of malaria parasites in the blood.
While a staggering 93 per cent of the placebo group had one or more infections, only 66 per cent of the vaccinated subjects acquired an infection and in those vaccinated subjects, who became infected, the time to infection was delayed.
The outcome represents 48 per cent protective efficacy by time-to-event analysis, and 29 per cent efficacy by proportional analysis. There were no differences in adverse events between the vaccinated group and the placebo group.
Commenting on the trial, Professor Ogobara Doumbo, Director of the Bamako Malaria Research Training Centre at the University of Bamako, Mali, said, “Those of us in countries where people’s lives are devastated by malaria have been waiting for a highly effective malaria vaccine for decades.”
Second trial
In the second trial, PfSPZ-CVac was administered to the nine subjects three times over eight weeks; the research demonstrated the three doses were also safe and effective when administered over just 10 days.
Scientists at the Vaccine Research Centre, National Institute of Allergy and Infectious Diseases (NIAID), U.S. National Institutes of Health found that assays of the subjects’ cellular immunity correlated with vaccine-induced protection.
A team from Antigen Discovery Inc. that studied the antibody responses of the nine protected individuals, identified 22 malaria parasite proteins that could be the targets of protective immune responses.
The clinical trial of the vaccine to evaluate alternative dosage regimens included 42 adult volunteers, 21-45 years old where 27 volunteers received PfSPZ-CVac at varying doses.
There was no difference in adverse events between volunteers who received the vaccine and those who received saltwater placebo.
They were enrolled, vaccinated and assessed under the direction of Dr Benjamin Mordmüller at the Institute of Tropical Medicine, University of Tübingen, Germany.
The German Centre for Infection Research funded the current trial with additional support from Sanaria.
Reactions
Reacting to the report, Prof. Martin Grobusch, Director of the Centre of Tropical Medicine at the University of Amsterdam’s Academic Medical Centre, said, “Travellers continue to be at high risk of acquiring malaria. A vaccine like PfSPZ-CVac that provides complete protective immunity for 10 weeks and can be administered in less than two weeks will be an ideal tool for the prevention of malaria in the travelling population.”
Sanaria Founder and CEO, Dr Stephen L. Hoffman, said, “These are extremely encouraging results as we have seen significant protection with a dosage regimen that we know to be sub-optimal.”
“We are now building on the protective efficacy seen in this first landmark study of efficacy of PfSPZ vaccine in Africa in current clinical trials of PfSPZ vaccine underway in Tanzania, Equatorial Guinea, Burkina Faso, Germany, the U.S., and of course in Mali.”
“We feel that we are moving rapidly toward establishing a dosage regimen that will provide the high-level protection needed by the billions of people at risk every day from this lethal disease,” he said.