The RTS,S/AS01 malaria vaccine reduced the incidence of malaria in infants by approximately one-third, researchers from the RTS,S Clinical Trials Partnership reported in The New England Journal of Medicine.
“We’ve made significant progress in recent years in our battle against malaria, but the disease still kills 655,000 people a year — mainly children younger than 5 years in sub-Saharan Africa,” Salim Abdulla, MD, PhD, director of the Ifakara Health Institute in Tanzania, said in a press release. “An effective malaria vaccine would be a welcome addition to our took kit, and we’ve been working toward this goal with this RTS,S trial.”
Abdulla and colleagues studied the vaccine in 6,537 infants aged 6 to 12 weeks, who were receiving their standard vaccines through the Expanded Program on Immunization. The children were assigned to three groups: group one received three doses of the vaccine plus a booster dose; group two received just the three doses; and group three received a nonmalaria vaccine.
During the 14 months after the first dose of vaccine, the incidence of clinical malaria was 0.31 per person-year in those who received the vaccine and 0.4 in those in the control group. This translated to a vaccine efficacy of 30.1% (95% CI, 23.6-36.1) for the intention-to-treat population. Against severe malaria, the vaccine efficacy was 26% (95% CI, –7.4 to 48.6) in the intention-to-treat population. In the per-protocol population, the vaccine efficacy was 31.3% (95% CI, 23.6-38.3). Against severe malaria, the vaccine efficacy was 36.6% (95% CI, 4.6-57.7) for the per-protocol population.
Adverse events were similar among the groups. Within 1 month of receiving the third dose, 99.7% of the infants who received the vaccine were positive for anti-circumsporozoite antibodies. The geometric mean titer was 209 endotoxin units (EU)/mL (95% CI, 197-222).
“The efficacy is lower than what we saw last year with the older 5- to 17-month-age category, which surprised some of use scientists at the African trial sites,” Abdulla said. “It makes us even more eager to gather and analyze more data from the trial to determine what factors might influence efficacy against malaria and to better understand the potential of RTS,S in our battle against this devastating disease.”
In an accompanying editorial, Johanna P. Daily, MD, of the division of infectious disease at Albert Einstein College of Medicine in Bronx, N.Y., said developing a malaria vaccine has been challenging, and although the vaccine efficacy reached 56% in a trial among children aged 5 to 17 months, the efficacy was much lower for this trial.
“The results of this trial suggest that this candidate malaria vaccine is not ready to become part of the routine panel of infant immunizations,” Daily wrote. “However, this trial did show protection in a subset of children and thus should be used as an opportunity to enlighten researchers regarding the host responses that correlate with vaccine protection.”
For more information:
The RTS,S Clinical Trials Partnership. N Engl J Med. 2012;doi:10.1056/NEJMoa1208394.
Daily J. N Engl J Med. 2012;doi:10.1056/NEJMe1213392.
Disclosure: Abdulla received funding from PATH Malaria Vaccine Initiative. Daily reports no relevant financial disclosures.