Health Secretary Robert F. Kennedy Jr. told the anti-vaccine group he founded that they had "a strong and steadfast friend at the White House" and that he would "die with my boots on" pursuing vaccine risk answers. His remarks to Children's Health Defense signaled a shift from earlier this year when White House officials pushed him to sidestep the vaccine issue.

The speech came a day after President Trump's surgeon general nominee, Dr. Nicole Saphier, defended vaccine safety and efficacy at her Senate confirmation hearing. Mr. Kennedy plunged into vaccines after discussing food safety and nutrition. He was preceded by Mark Gorton, president of the MAHA Institute, who called the polio vaccine's success a "fraud," and followed by Andrew Wakefield, the discredited British doctor whose retracted paper linked the MMR vaccine to autism.

With midterms less than two months away, Mr. Kennedy is rallying his Make America Healthy Again followers. He promised to "be in this fight" to the end and said his team was launching studies. He drew applause when announcing he would examine health effects of electromagnetic radiation and chemtrails.

President Trump recently signed an executive order limiting childhood vaccines and falsely called the measles shot "lethal." Dr. Mehmet Oz later corrected him on CBS's "Face the Nation." Measles cases have surpassed a 35-year record with about 3,300 cases, and Pennsylvania reported a fourth death this week.