Pfizer's stock dropped 4.3 percent while Moderna's fell 3.1 percent and Novavax saw a 2.8 percent dip in its stock Friday morning.

Donald Trump's pick for head of Health and Human Services is trying to walk back his anti-vaxxer past — but still sowing doubt for the life-saving public health measure

Robert F. Kennedy Jr. wants to revisit federal vaccine recommendations, take fluoride out of public water and boost access to raw milk, among other goals.

Donald Trump wants Robert F. Kennedy Jr. to be his health and human services secretary. But Kennedy has spread misinformation about vaccines, fluoride, raw milk and other health topics. Here's what he has said.

Vaccines are most effective at scale when enough people get them to provide "herd immunity" from a virus, doctors and officials say.