Babies need vitamin K to help their blood clot, but they aren’t born with enough of it in their system. Two researchers were awarded the Nobel Prize in 1943 for their discovery of vitamin K and its ability to form clots and stop bleeding in babies, and the vitamin K shot has been a standard intervention for newborns in the U.S. since the American Academy of Pediatrics recommended it more than 60 years ago.

But in recent years, parents have started refusing the shot. Although the vitamin K shot is not a vaccine, it has become entangled in the anti-vaccine movement. False and misleading information online has led some parents to believe the shot is harmful. In addition, some parents have voiced a desire for a more natural birthing experience, one without pharmaceutical intervention. And some simply don’t want their babies to go through the pain of an injection that they don’t believe is necessary.