The Gates Foundation announced Tuesday that it is pledging $1.6 billion over five years to Gavi, the Vaccine Alliance.

Gavi CEO Sania Nishtar reported that the nonprofit has vaccinated 1.1 billion children in 78 low-income countries since its inception in 2000, and estimates that 19 million deaths were prevented as a result. It has been the Gates Foundation’s biggest grantee in the vaccine industry, receiving $7.7 billion prior to this announcement.