The world's first malaria vaccine is being rolled out in parts of Kenya starting Friday, having already been released in Ghana and Malawi.

It will be added to the routine immunization schedule and more than 300,000 children are expected to receive the vaccine over the next three years.

Malaria kills more than 400,000 people every year worldwide, mostly children, which could change the game, said world health correspondent Tulip Mazumdar.