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Malaria Vaccine May Be Working – Huge Event with a Global Impact

 

The efficacy and safety of the RTS,S/AS01 candidate malaria vaccine during 18 months of follow-up have been published previously. The current report, published online in The Lancet (23 April 2015), reports the final results from the same trial, including the efficacy of a booster dose.

 

We are all in this together: The trial was sponsored by GlaxoSmithKline Biologicals SA (GSK), the vaccine developer and manufacturer, and funded by both GSK Biologicals SA and the PATH Malaria Vaccine Initiative (MVI). GlaxoSmithKline Biologicals SA received a grant from MVI to run the trial and MVI received a grant from the Bill & Melinda Gates Foundation to run this trial.

 

Between March 2009 and January 2011, children (age 5-17 months) and young infants (age 6-12 weeks) were enrolled at 11 centers in seven countries in sub-Saharan Africa. Participants were randomly assigned (1:1:1) at first vaccination by block randomization with minimization by center to receive three doses of RTS,S/AS01 at months 0, 1, and 2 and a booster dose at month 20 (R3R group); three doses of RTS,S/AS01 and a dose of comparator vaccine at month 20 (R3C group); or a comparator vaccine at months 0, 1, 2, and 20 (C3C [control group]). Participants were followed up until Jan 31, 2014. Cases of clinical and severe malaria were captured through passive case detection. Serious adverse events (SAEs) were recorded. Analyses were by modified intention to treat and per protocol. The coprimary endpoints were the occurrence of malaria over 12 months after dose 3 in each age category. Vaccine efficacy (VE) against clinical malaria was analyzed by negative binomial regression and against severe malaria by relative risk reduction.

 

8,922 children and 6,537 young infants were included in the modified intention-to-treat analyses. Children were followed up for a median of 48 months and young infants for 38 months after dose 1. From month 0 until study end, compared with 9,585 episodes of clinical malaria that met the primary case definition in children in the C3C group, 6,616 episodes occurred in the R3R group (VE 36.3%) and 7,396 occurred in the R3C group (28.3%, 23?3-32?9); compared with 171 children who experienced at least one episode of severe malaria in the C3C group, 116 children experienced at least one episode of severe malaria in the R3R group (32.2%) and 169 in the R3C group (1?1%). In young infants, compared with 6,170 episodes of clinical malaria that met the primary case definition in the C3C group, 4,993 episodes occurred in the R3R group (VE 25.9%) and 5,444 occurred in the R3C group (18?3%); and compared with 116 infants who experienced at least one episode of severe malaria in the C3C group, 96 infants experienced at least one episode of severe malaria in the R3R group (17.3%) and 104 in the R3C group (10.3%). In children, 1,774 cases of clinical malaria were averted per 1,000 children in the R3R group and 1,363 per 1000 children in the R3C group. The numbers of cases averted per 1,000 young infants were 983 in the R3R group and 558 in the R3C group.

 

The frequency of SAEs overall was balanced between groups. However, meningitis was reported as a SAE in 22 children: 11 in the R3R group, ten in the R3C group, and one in the C3C group. The incidence of generalized convulsive seizures within 7 days of RTS,S/AS01 booster was 2.2 per 1,000 doses in young infants and 2.5 per 1,000 doses in children.

 

According to the authors, RTS,S/AS01 prevented a substantial number of cases of clinical malaria over a 3-4 year period in young infants and children when administered with or without a booster dose. Efficacy was enhanced by the administration of a booster dose in both age categories. Thus, the vaccine has the potential to make a substantial contribution to malaria control when used in combination with other effective control measures, especially in areas of high transmission.

 

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