Abstract

• Malaria remains a major public health problem in most tropical countries. Plasmodium falciparum infection can be life-threatening, especially in children. Insecticide-treated bed nets have been shown to reduce deaths due to malaria among young children.
   
• A malaria vaccine (RTS,S/AS01E) containing two adjuvants has been assessed for its ability to prevent P. falciparum malaria among young children living in endemic areas. The clinical data have been analysed by the European Medicines Agency (EMA) in cooperation with the World Health Organization (WHO).
   
• Efficacy has been evaluated in sub-Saharan African countries. Two trials including a total of more than 16 000 children aged 6 weeks to 17 months compared the malaria vaccine with a rabies vaccine or a meningococcal vaccine. Most of the children were healthy, had ready access to healthcare, and were protected with bed nets.
   
• In these trials, three injections of the malaria vaccine one month apart did not reduce overall mortality or malaria mortality in low-mortality settings. In the year following vaccination, the risk of malaria episodes was reduced by about 30% among children aged 6 to 12 weeks and by about 50% among those aged 5 to 17 months. The incidence of severe malaria was only reduced in the older age group. Vaccine efficacy waned rapidly over time, even with a booster dose at 18 months.
   
• During clinical trials, reactions at the injection site and systemic reactions were more frequent with the malaria vaccine than with the comparator vaccines. Febrile seizures during the days following vaccination were 2 to 5 times more frequent with the malaria vaccine among children aged 5 to 17 months. The malaria vaccine may also carry a risk of meningitis, as well as a risk of pneumonia among HIV-infected children and premature infants. 
   
• In summary. In two trials involving more than 16 000 sub-Saharan African children aged 6 weeks to 17 months, the RTS,S/AS01E malaria vaccine did not reduce overall mortality or mortality due to malaria. It roughly halved the frequency of malaria episodes but only prevented severe disease in children over 5 months old. Efficacy declined rapidly over time, despite administration of a booster dose. In addition to local and systemic adverse effects, this malaria vaccine may increase the risk of meningitis and pneumonia in some children.
   
• In late 2016, the harm-benefit balance of the RTS,S/AS01E malaria vaccine is highly uncertain, but its evaluation must continue where the vaccine is much needed.

©Prescrire 1 January 2017

"RTS,S/AS01E malaria vaccine (Mosquirix°) Children living in malaria-endemic regions: little efficacy, poorly documented harms" Prescrire Int 2017; 26 (178): 5-8. (Pdf, subscribers only)