The rollout of malaria vaccines in a regular immunisation programme marks a "turning point" in the fight against the disease, Aurelia Nguyen, chief programme officer of the Gavi vaccine alliance, told AFP.
The mosquito-borne disease kills more than 600,000 people a year, mainly in Africa, according to the World Health Organization.
Following a pilot phase, the RTS,S vaccine is being rolled out at scale across the continent -- starting in Cameroon on Monday.
Why is the rollout so important?
Nguyen: "It's a historic day. Up to now we had done a small-scale pilot in three countries -- Kenya, Ghana and Malawi -- to understand how to use the vaccine. Now in Cameroon we are going straight into routine immunisation.
"This is truly a turning point. We have been working on the malaria vaccine for a very long time. It took 30 years. It is a challenging disease because it is transmitted by a parasite with a very complicated life cycle.
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"We (now) have a weapon which has proven to be safe and effective.
"There had been a lot of progress in the fight against malaria but we had reached a point where this progress was slowing down. In some countries, cases, hospitalisations and deaths were starting to rise. There are various causes: global warming, population movements."
Why Cameroon and where next?
Nguyen: "We decided to concentrate first where the need was greatest. Cameroon is one of the countries where disease incidence is fairly high.
"So we focused on Cameroon because that's where the vaccine will really have a positive impact.
"In Cameroon, 30 percent of consultations are linked to malaria. Having a preventative tool like the vaccine will free up the health system and result in fewer hospitalisations and deaths.
"We are working to start rolling out the vaccine in as many countries as possible. Thirty countries have shown an interest.
"We hope to have a fairly broad rollout within the next two years.
We are focusing first on the areas most at risk, and then bit by bit we will be able to expand, depending on what the countries want.
"Other countries have already had doses and are carrying out the implementation, preparation and training, for example Burkina Faso and Senegal."
Are other continents interested?
Nguyen: "It's a mosquito-borne disease, and we notice that the zones where mosquitos proliferate are increasing. The range of mosquitos is widening.
"So we see them in India, in southern Europe, elsewhere in Asia or Latin America, and this is where there could be other interested countries.
"We are starting to have these discussions and if these countries are eligible for Gavi support, they would be entitled to the same programme that we are doing in Africa."
Agence France-Presse