A four year trial found that the RTS,S/AS01E malaria vaccine was only 16.8% effective.
In highly variable results, vaccine efficacy declined over time — from 43.6% in the first year to almost zero in the fourth year — and with increasing exposure to malaria.
For every 100 vaccinated children, 65 cases of clinical malaria were averted. Multiple episodes of malaria were common, with 551 cases among 118 of the 223 children who received the vaccine.