WASHINGTON — Chris Klomp, President Donald Trump’s nominee to become deputy health secretary, told senators Tuesday that fighting the nation’s measles outbreak would be a top priority and that the measles-mumps-rubella vaccine remains the strongest public health defense against the disease. “Unquestionably, the MMR vaccine is the single most effective public health tool that we have against measles,” Klomp said during his confirmation hearing before the Senate Finance Committee. Klomp has served since February as chief counselor to Health Secretary Robert F. Kennedy Jr. and has overseen day-to-day operations at the Department of Health and Human Services. His testimony came as the United States reported nearly 3,300 measles cases this year, the highest total in 35 years. Democratic senators pressed Klomp to explain his position on vaccination amid repeated controversies involving Trump administration health nominees. Kennedy and Trump have questioned vaccine safety in recent months, while several nominees have struggled to affirm the shots’ safety without contradicting their political superiors. Asked what advice he would give parents, Klomp said they should consult their children’s pediatricians. He also acknowledged that HHS strongly recommends measles vaccination, while adding that the department should continue studying the safety of licensed medical interventions. Klomp took a more guarded position when senators asked about claims that the MMR vaccine contains fetal tissue. Kennedy said last month on social media that it did. The American Academy of Pediatrics has rejected that claim, explaining that some vaccines use viruses grown in cell cultures originally developed from two abortions in the 1960s, but that fetal tissue is not present in the vaccines produced today. Klomp said he was not a vaccine expert but told senators he did not believe the vaccine contains fetal tissue today. He also defended Trump’s August executive order calling for the combined MMR shot to be made available as separate measles, mumps and rubella vaccinations. Klomp said the goal was to reach parents who are uneasy about combination vaccines and encourage them to protect their children against measles. Sen. Maggie Hassan, a New Hampshire Democrat, challenged that explanation, saying it was difficult to reconcile the administration’s stated desire for children to receive fewer shots with a policy that could require more injections. She also said there was no scientific evidence that separating the vaccines would improve safety. Sen. Michael Bennet, a Colorado Democrat, similarly questioned the rationale for splitting the vaccine. Klomp repeatedly sought to separate his own responsibilities from the policy positions of Kennedy and Trump. He said his role as chief counselor has centered on keeping HHS functioning rather than setting department policy. On scientific oversight, Klomp promised to maintain rigorous standards, including qualified lead researchers, independent peer review and a commitment to publish results regardless of whether they support the department’s preferred conclusions. He said poor-quality research would not be tolerated and pledged to dismiss anyone who failed to follow the scientific method. Klomp’s nomination will also face scrutiny over his role in negotiating agreements with pharmaceutical companies to lower prescription drug prices and expand domestic manufacturing. Democrats have criticized the administration for withholding the terms of those agreements. The Finance Committee will decide whether to advance his nomination to the full Senate. Klomp is scheduled to appear before the Senate health committee Wednesday.