While many officials and scientists embrace other parts of the secretary’s agenda, his stance on vaccines is alienating allies who fear a public health crisis.

That kind of shot was first used during the Covid-19 pandemic, but the health secretary has been sharply critical of the technology.

Robert F. Kennedy Jr. has halted funding for mRNA shots. We explore why.

While many officials and scientists embrace other parts of the secretary’s agenda, his stance on vaccines is alienating allies who fear a public health crisis.