Gavi works to expand access to vaccines for children in some of the world’s poorest countries. Health experts say the move could have deadly consequences.

Gavi has paid for more than 1 billion children to be vaccinated through routine immunization programs, saving an estimated 18 million lives.

The U.S. will no longer contribute funding to Gavi, a global alliance that helps buy vaccines for the world's poorest children, because it ignores safety, Health Secretary Robert F. Kennedy Jr. said on Wednesday,