Most supporters of the anti-vaccination movement advocate for “natural” disease prevention, such as taking lots of vitamins to bolster the immune system. So why are they opposing using vitamin K to treat babies born with a deficiency? Because it’s delivered by injection, of course.

The family of similar molecules known as vitamin K modify blood proteins so that they bind to calcium ions, allowing clotting. Most people get all the vitamin K they need from their diet, particularly green leafy vegetables, although some conditions result in deficiencies.

However, the situation for infants is different, particularly newborns. Vitamin K deficiencies occur in 2-10 cases out of 100,000, with symptoms appearing anywhere in the first 12 weeks of life.

While the consequences can be life-threatening, with severe bleeding potentially leading to brain damage or death, in the developed world there is a simple treatment – intramuscular vitamin K1 injections. All newborns in the USA are now given a routine vitamin K shot, removing the risk entirely.

However, Vanderbilt University’s Monroe Carell Jr. Children’s Hospital has reported eight cases of Vitamin K Deficient Bleeding (VKDB) in the last year. Descriptions of the first four cases should be enough to get any parent to agree to their child getting the supplement, but it seems not.

A Centers for Disease Control study on why parents refuse vitamin K shots found, "Reasons included concern about an increased risk for leukemia when vitamin K is administered, an impression that the injection was unnecessary, and a desire to minimize the newborn's exposure to 'toxins.'"

The American Academy of Pediatrics, have concluded, "Earlier concern regarding a possible causal association between parenteral [injected] vitamin K and childhood cancer has not been substantiated.” Moreover, even if such an association did exist, the danger would be orders of magnitude lower than that from VKDB.

Unfortunately, as Chris Mooney points out in Mother Jones, the forces of evidence-based medicine are fighting against a tide of misinformation, spread mainly by the well-known anti-vaccine advocates, who call the injections “a terrible assault to a baby’s suddenly overloaded sensory system.”

Vitamin K can be administered orally but this has been shown to be less effective than via injection, as the baby may vomit up the dose, and parents often forget to stick to the regime.

One of the problems with favoring ideology over evidence is that, once started, it’s hard to stop. As Amanda Marcotte says at Slate, “The anti-vaccination movement has morphed into an anti-shot movement, and it's children who are paying the price.”