The World Health Organization (WHO)-approved RTS,S vaccine, developed by British drugmaker GSK, is targeting infants in Cameroon's 42 worst-affected districts.

The central African country will be the first country to administer doses through a routine immunisation programme, following successful pilot campaigns in Kenya, Ghana and Malawi.

The rollout, due to start on Monday, was described by health officials as a milestone in the decades-long effort to curb malaria in the continent.

Twenty other countries aim to roll out the programme this year, according to global vaccine alliance Gavi.

The four-dose vaccine is only about 30% effective and protection begins to fade after several months.

GSK said it can only produce about 15 million doses a year.