If Robert F Kennedy Jr has an arch-nemesis, then it is probably Dr Paul Offit.

The paediatrician is a doctor of global significance. He happens to be one of the inventors of the rotavirus vaccine (RotaTeq), which has saved thousands of infant lives since it was rolled out twenty years ago.

But the 75-year-old has, in these dark times of misinformation and bonkers conspiracy theories, railed at the rise of RFK Jr and his anti-science cronies.

“He is an evil, evil man and I have such hatred for him,” he said recently. “I will do everything I can every day to hold up to the light what he is doing to America’s children.”