WASHINGTON (AP) — President Donald Trump on Monday signed an executive order calling for revamped childhood vaccine recommendations that promote his long-held but discredited theory that childhood shots should be spaced out into separate medical visits.

The order advocates separating the measles, mumps and rubella (MMR) vaccine into three different shots administered in separate appointments, and directs the nation’s health department to improve vaccine research, according to a White House fact sheet on the order.

Separate measles, mumps and rubella vaccines for children are not currently available in the United States, and vaccines are already extensively researched.