When Robert F. Kennedy Jr. was confirmed as America’s secretary of health and human services, neutral observers might have asked themselves: Would it be possible for a lawyer who had questioned the safety of childhood vaccinations for two decades to look at the available data and reconsider his views?

Experts say vitamin A can mitigate measles but does not protect those who are unvaccinated from getting the disease, and RFK Jr. says immunization is a "freedom of choice."