Samoa was on the brink of catastrophe in 2019. An improperly prepared measles vaccine killed two babies, and when vaccinations resumed, many parents were still wary. Thousands of small children were left unprotected against a highly contagious disease resurging across the globe.

Robert F. Kennedy Jr., then the chairman of an anti-vaccine nonprofit, saw an opportunity for a national study that would track health outcomes in the absence of widespread vaccine use — months before a deadly measles outbreak killed 83 people and sickened thousands.

The subject will no doubt be raised during Kennedy’s Senate confirmation hearing for secretary of health and human services next Wednesday.