Children in Ghana, Kenya and Malawi have been selected to trial the world's first malaria vaccine, which the World Health Organisation (WHO) says could save "tens of thousands of lives".
Around 750,000 children aged between five months and 17 months will receive injections designed to reduce their risk of contracting malaria, which kills more than 400,000 people per year.
How does the vaccine work?
British pharmaceutical giant GlaxoSmithKline's RTS,S, also known by its trade name Mosquirix, "trains the immune system to attack the malaria parasite, which is spread by mosquito bites", says the BBC.
Trials showed it cut the risk of malaria by 40 per cent. WHO regional director Dr Matshidiso Moeti said that, combined with existing measures such as mosquito nets and insecticides, the vaccine could save "tens of thousands" of lives.
Why only three countries?
Ghana, Kenya and Malawi were chosen "because all have strong prevention and vaccination programs but continue to have high numbers of malaria cases".
To be effective, the vaccine has to be administered once a month for three months, then again 18 months later, which could be challenging in poor and remote regions that only have sporadic access to healthcare.
The three pilot schemes will determine whether larger-scale implementation is feasible.
"Information gathered in the pilot programme will help us make decisions on the wider use of this vaccine," Moeti said.