Kennedy, seeking to defend against past anti-vaccine remarks, said he wants HHS under his potential leadership to have a "gold standard" and "evidence-based science."

"And if you show me where I'm wrong on this, show me a single statement I made about science that is erroneous," he said.

Kennedy made a number of false or unfounded statements regarding vaccines, pesticides, and more. A fact-check of some of his claims during his first confirmation hearing can be found here.

Democrats, and some Republicans, are confronting Kennedy throughout this hearing and have been pointing to data that shows vaccines like those for measles, polio, HPV and more are safe.

Data from the Centers for Disease Control and Prevention shows the HPV vaccine is safe and effective despite past statements from Kennedy that the HPV vaccine is "dangerous" and increases the risk of cervical cancer.

"Do you stand by those statements, yes or no?" Sen. Patty Murray, of Washington, asked.

"I stand by your previous statement. I litigated on that issue. I represented hundreds of young girls who felt that they were injured by the vaccine," Kennedy replied.

Kennedy has referred clients to a firm suing Merck over claims that it failed to communicate alleged risks of its HPV vaccine.

The HPV vaccine was recommended in 2006 in the U.S, for routine vaccination at age 11 or 12.

The HPV vaccine is safe and effective, according to the CDC. Data shows that in the 10 years after the vaccine was recommended in 2006 in the United States, infections with four strains of HPV infections decreased by 86% in female teens ages 14 to 19 and 71% in women in their early 20s.

Democratic Sen. Tammy Baldwin pressed for a commitment from Kennedy to keep mifepristone on the market. Kennedy said he wouldn't get ahead of President Donald Trump on the issue.

"President Trump has not chosen a policy," Kennedy said. "I will implement his policy."

Trump shifted his stance on abortion access throughout the 2024 campaign, largely saying it's a state issue. He avoided speaking in depth on his view on the abortion pill. The Biden administration vigorously pushed back against legal challenges brought against mifepristone that arose after the fall of Roe v. Wade.

Republican Sens. Bill Cassidy and Rand Paul, both doctors, had a brief argument over the Hepatitis B vaccine for infants.

Cassidy defended the vaccine's efficacy amid Paul's questioning of some of its uses: "A vaccine on day one of life prevents chronic Hepatitis B 95% of the time."

Cassidy, a doctor from Louisiana, is the chairman of the Senate HELP Committee.

During Wednesday's hearing with the Senate Finance Committee, Cassidy had a tense exchange with Kennedy over Medicare and Medicaid.

Leaving the hearing, Cassidy wouldn't say whether he was satisfied with his answers.

"I'm not commenting on anything about RFK until after all the process is over," Cassidy told ABC's Allison Pecorin.

Kennedy can only afford to lose three Republican votes, should all Democrats oppose his nomination -- as is expected.