The most clinically advanced malaria vaccine so far should be ready for use in three to five years after Phase three trials began in May, researchers said Tuesday.

The vaccine -- known as the RTS,S -- is targeted to be at least 50 percent effective against the severe form of malaria and to last up to one year.

- We believe and hope that in three to five years from today we will be able to put the vaccine in use - Joe Cohen, the vaccine's co-inventor and a GlaxoSmithKline researcher told AFP.

Up to 16,000 children aged between six weeks to 17 months in seven African countries -- Burkina Faso Gabon, Ghana, Kenya, Malawi, Mozambique and Tanzania -- will be vaccinated.

- This is a tremendous moment in the fight against malaria and the culmination of more than two decades of research, including 10 years of clinical trials in Africa - said Cohen.

Malaria is the world's deadliest infectious disease. It kills around 900,000 people every year, mainly children under five in sub-Saharan Africa.

Phase three tests monitor safety and potential side effects and evaluate efficacy on a large scale.

Results of Phase 2 trials, which were announced last year, showed 53 percent efficacy against clinical malaria in young children.

If successful, the phase three testing and license of the vaccine would make it a "first generation malaria vaccine that is at least 50 percent effective against severe disease and death and lasts more than one year," said the Malaria Vaccine Initiative.

The vaccine is primarily intended for infants and children under five who are the most vulnerable to malaria.

In 2006, the international community set a long-term goal of having by 2025 a malaria vaccine that would be at least 80 percent effective against the less severe forms of the disease and last longer than four years.

The experts made the vaccine trial announcement during the fifth Multilateral Initiative on Malaria conference in the Kenyan capital Nairobi.

Other vaccines are also undergoing trials, but have not reached the advanced Phase three stage.

The health experts and researchers are also seeking ways to eradicate the disease through vector control such as using long-lasting insecticide bednets and indoor spraying.

More effective drugs are also being researched to tackle emerging resistance as well as medicines for the less severe but more widespread malaria type -- Plasmodium vivax.

The Nairobi conference began on Sunday and will close on Friday.