Sen. Rand Paul said Tuesday that he does not think the government should require people to receive vaccinations, amid a heated debate over the growing influence of anti-vaccine groups and as Washington state experiences its worst measles outbreak in more than two decades.

Paul (R-Ky.) made similar comments ahead of his unsuccessful White House bid in 2016. On Tuesday, he was the sole lawmaker to strike a defiant tone on the topic at a hearing of the Senate Health, Education, Labor and Pensions Committee.

Paul said that he and his children have been vaccinated, and that in general, he believes “the benefits of most vaccines vastly outweigh the risks.” But he added that he supports “persuasion” rather than government-mandated vaccines.

“It is wrong to say that there are no risks to vaccines. Even the government admits that children are sometimes injured by vaccines . . . I still don’t favor giving up on liberty for a false sense of security,” Paul said.

The rise of the anti-vaccine movement, facilitated in part by social media, has prompted an alarming resurgence of measles in states across the country. The deadly disease was declared eliminated from the United States in 2000, according to the Centers for Disease Control and Prevention. But public health officials are now scrambling to keep the highly contagious virus from once again spreading out of control, particularly among under-vaccinated populations in states such as Washington, Oregon and Idaho.

At Tuesday’s hearing, Paul acknowledged that those who are not vaccinated could spread diseases to immunocompromised people. But he claimed that “there doesn’t seem to be enough evidence of this happening to be reported as a statistic.”

The recent measles outbreak in the Pacific Northwest has sickened at least 75 people, most of them unvaccinated children under 10. Globally, cases of measles are surging to alarmingly high levels, UNICEF recently warned.

But Paul appeared to play down the seriousness of the situation, asking, “If the fear of this is valid, are we to find that next we’ll be mandating flu vaccines?”

In 2015, as he was mulling a presidential bid, Paul said in interviews on CNBC and with conservative radio host Laura Ingraham that he believed the choice to vaccinate should be up to parents rather than mandated by the government.

In the CNBC interview, he claimed to have “heard of many tragic cases of walking, talking normal children who wound up with profound mental disorders after vaccines.”

“I’m not arguing vaccines are a bad idea; I think they’re a good thing,” Paul, who is an ophthalmologist, said at the time. “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.”

Asked Tuesday what the senator meant by parents “owning” their children, Paul’s spokesman, Sergio Gor, said that Paul was emphasizing that “at the end of the day, parents should have a say about what happens to their kids.”

The notion that vaccines might cause autism has its roots in fraudulent research that was debunked nearly a decade ago and was recently refuted again in a study of more than half a million people.

Lena H. Sun contributed to this report.

Correction: An earlier version of this report incorrectly stated that Paul had questioned whether the benefits of vaccinations outweigh the risks. The article has been corrected.