By Kate Kelland

LONDON (Reuters) - Funding for phase one of pilot deployments of the world's first malaria vaccine in sub-Saharan Africa has been secured and immunization campaigns will begin in 2018, the World Health Organization (WHO) said on Thursday.

The vaccine, known as RTS,S or Mosquirix and developed by British drugmaker GlaxoSmithKline, is only partially effective and needs to be given in a four-dose schedule, but is the first approved shot against the mosquito-borne disease.

The WHO said last year that while RTS,S was promising, it should be deployed only on a pilot basis before any wide-scale use, given its limited efficacy.

Pedro Alonso, director of the WHO's Global Malaria Programme, said on Thursday that securing funding and being able to trial the vaccine in Africa pilots would be a milestone in the fight against malaria.

"These pilot projects will provide the evidence we need from real-life settings to make informed decisions on whether to deploy the vaccine on a wide scale," he said.

The go-ahead comes after the Global Fund to Fight AIDS, Tuberculosis and Malaria on Thursday approved $15 million for the malaria vaccine pilots, assuring full funding for the first phase of the programme.

Earlier this year, the GAVI Vaccine Alliance and UNITAID announced commitments of up to $27.5 million and $9.6 million respectively for the first four years of the programme.

Malaria infects around 200 million people a year worldwide and killed an estimated 440,000 in 2015. The vast majority of malaria deaths are among babies in sub-Saharan Africa.

RTS,S was developed by GSK in partnership with the non-profit PATH Malaria Vaccine Initiative and part-funded by the Bill & Melinda Gates Foundation.

(Reporting by Kate Kelland; Editing by Mark Potter)