After more than a decade of clinical research and $300 million in investment, the world's leading experimental malaria vaccine passed an important milestone last month. On 18 October, researchers reported the first phase 3 trial data showing that the vaccine against the Plasmodium falciparum parasite—known as RTS,S or Mosquirix—cut the risk of malaria infection after one year by 56% in a study of 6,000 infants aged 5–17 months old (N. Engl. J. Med. doi:10.1056/NEJMoa1102287, 2011).

“It's a huge step forward,” says study coauthor Pedro Alonso, director of the Barcelona Centre for International Health Research. “This is the first time that, truly, conclusively, one can show that one can produce protective immune responses in African children.”

It's been a long and winding road for the RTS,S vaccine. GlaxoSmithKline's product first hit a few snags during early trials in adults. But, with the focus shifted to protecting the young, researchers are confident that the vaccine is well on its way to widespread use in children. Here we chronicle the major steps along the path of RTS,S's clinical development.

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