The hearing, convened by the Senate Health, Education, Labor and Pensions (HELP) committee, on which Paul sits, coincided with a classified hearing on Iran’s nuclear negotiations, which Paul attended, according to a spokesman.
“He was attending a classified Foreign Relations committee hearing at the exact same time,” Sergio Gor, a spokesman for Paul, told ABC News.
Paul stirred controversy when he said during a TV appearance last week that he heard cases of perfectly healthy children who wound up with medical issues after getting vaccinated.
"I'm not arguing vaccines are a bad idea. I think they are a good thing. But I think the parent should have some input. The state doesn't own your children. Parents own the children, and it is an issue of freedom,” Paul added during the segment.
Later, Paul clarified his comments, saying he supported vaccines and wasn’t saying vaccines caused disorders – only that they were “temporally related” – and also tweeted a picture of himself getting a booster shot.
They were also prepared for the possibility he wouldn’t attend the hearing at all: “What will he say today? Will he show up to the hearing? Or will he skip it altogether?”
Senators frequently have overlapping obligations that force them to miss hearings and other events, but more than half the members on this committee were able to attend, as The Hill pointed out.
ABC's Arlette Saenz contributed to this report.