It reads: “There is a large body of evidence to show that MMR vaccine is highly effective and only rarely causes serious side effects. This is from research studies as well as from years of experience using MMR vaccine. “We therefore have no research evidence about the safety and effectiveness of the single vaccines used in this way as well as no experience. Among those criticising the US president’s new executive order is Louisiana senator Bill Cassidy, who said it was “wrong” and that Trump “does not have the expertise to make these changes”. “Parents should listen to their child’s pediatrician about vaccines rather than listening to an inaccurate executive order.