Kennedy has touted the benefits of an unconventional measles treatment including the steroid budesonide, the antibiotic clarithromycin and cod liver oil, which has high concentrations of vitamin A.

In an interview, the H.H.S. secretary claimed that unconventional treatments were helping patients but described vaccination as a personal choice.

RFK Jr. has cited vitamin A and cod liver oil as effective methods of measles prevention while stopping short of outright suggesting vaccines.

Kennedy wrote in an opinion piece published Sunday on Fox News Digital that parents should consult with physicians about the MMR vaccine.