Malaria Vaccine Trial Yields Promising Results
by Justine Alford
Photo credit: AFPMB, “Anopheles gambiae,” via Flickr. CC BY-NC-ND 2.0. This mosquito is the primary vector for malaria transmission in the majority of sub-Saharan Africa.
Each year, it is estimated that at least 200 million malaria cases. At least 600,000 of those are fatal. While anti-malarial treatments and preventative measures such as insecticides and mosquito nets have reduced the global burden of disease by 45% since 2000, the emergence of insecticide and drug resistance is becoming a major hurdle in tackling this problem. Therefore, there exists a need for an effective malaria vaccine to overcome these issues and further reduce malaria incidence, especially in areas where transmission is still high.
Although no malaria vaccines are licensed at present, one candidate vaccine, RTS,S/AS01, is currently undergoing phase III clinical trials in several countries in Africa. Now, the results from an 18-month efficacy and safety investigation are in, and it’s looking promising.
For the study, 6,537 babies between the ages of 6-12 weeks and 8,923 children between the ages of 5-17 months were randomly assigned either 3 doses of the candidate vaccine or a control vaccine. The participants were then followed up for the next year and a half in order to determine rates of malaria and any possible adverse events.
As reported in PLOS Medicine, they found that the vaccine efficacy against clinical malaria was 46% in children and 27% in infants. Although this may sound modest, it actually averted an average of 829 cases of malaria per 1,000 children vaccinated across all study sites. While the efficacy was found to wane over time, over the 18 month period it prevented a significant number of cases of malaria and was particularly effective in regions with the highest incidence of malaria.
With regards to safety, they did find that the occurrence of one serious adverse event, meningitis, was higher in those given the malaria vaccine compared with those receiving the control. They cannot prove that it was the vaccine that caused this since it is only an association, but the researchers will keep a close eye on this for the remainder of the trial.
Taken together, this trial has demonstrated that even a modest vaccine efficacy can have a significant impact on malaria cases. This vaccine may therefore be an effective way to curb malaria in areas where the disease remains a burden, such as sub-Saharan Africa, especially if used in conjunction with other preventative measures such as mosquito nets and insecticide.
As a result of this promising study, the vaccine manufacturers, GlaxoSmithKline, have now applied for regulatory approval; so far no other candidate malaria vaccines have reached this far. If successful, the vaccine could be approved for use as early as next year.
For now, researchers will continue with the trial to see how long protection lasts, and to investigate whether a booster will improve efficacy.
Via PLOS Medicine and BBC News