Two Republican senators say they have not decided how they will vote on President Donald Trump’s nominee for surgeon general, Dr. Casey Means, raising questions about her ability to secure confirmation, Politico reported.

Senators Susan Collins, R-Maine, and Lisa Murkowski, R-Alaska, said they remain undecided after Means’s confirmation hearing, where she was questioned on vaccines, psychedelic therapy, and other health matters. If all Democrats on the Senate Health, Education, Labor, and Pensions Committee vote against Means, even a single Republican “no” could block her from advancing.

In her hearing, Means said she supports vaccines but did not rule out exploring a potential link between vaccines and autism. “We do not know what, as a medical community, causes autism,” she said. “We should not leave any stones unturned.” She emphasized that conversations between patients and physicians are essential.

Collins raised questions about Means’ past use of psychedelic drugs and her book advocating “psilocybin-assisted therapy,” telling Means, “I’m concerned.” Murkowski cited concerns over vaccine skepticism and assurances from last year’s Health and Human Services Secretary confirmation that she feels have not been met.

Several committee Republicans, including Sens. Roger Marshall, Tommy Tuberville, Josh Hawley, Jim Banks, Markwayne Mullin, and Jon Husted, said they support Means and would vote to confirm. Sens. Tim Scott and Ashley Moody declined to comment. Committee Chair Bill Cassidy, R-La., also did not disclose his vote.

The outcome of Means’ confirmation remains uncertain as senators weigh her positions and past statements ahead of a key committee vote.