Washington (CNN) — The Senate voted on Thursday to confirm Robert F. Kennedy Jr. Health and Human Services Secretary, a victory for President Donald Trump after Kennedy faced intense scrutiny over his controversial views on vaccines and public health policy.

The 52-48 vote was largely along party lines, though Republican Sen. Mitch McConnell of Kentucky once again joined with Democrats to oppose the nomination.

McConnell has now voted against three of Trump’s Cabinet nominees, more than any other Republican senator.

The confirmation vote highlights the extent of Trump’s influence over the Senate GOP majority, as a slate of contentious nominees who faced questions over whether they could be confirmed – including Kennedy, Pete Hegseth as defence secretary and Tulsi Gabbard as director of national intelligence – have been approved by Senate Republicans for top administration posts.

McConnell, who also opposed the confirmations of Hegseth and Gabbard, has undergone an evolution in his party, moving from establishment leader to a key swing vote.

McConnell has had a strained relationship with Trump and others in the MAGA sphere for years, in part due to his opposition to the Republican party’s growing isolationist streak.

Kennedy will now serve as one of the nation’s leading public health officials.

The US Department of Health and Human Services is comprised of a number of key federal health agencies, including the Food and Drug Administration, the National Institutes of Health, the Centers for Medicare and Medicaid Services, and the Centers for Disease Control and Prevention.

During confirmation hearings on Capitol Hill, Kennedy denied being anti-vaccine, telling senators instead that he is “pro-safety.” He went on to say, “I believe that vaccines play a critical role in health care.”

At one point, Sen. Bernie Sanders, a Vermont independent, asked Kennedy if he agreed that the evidence shows vaccines do not cause autism, citing dozens of studies.

Kennedy began to say, “If you show me those studies, I will absolutely –,” at which point Sanders jumped in to say, “That is a very troubling response because the studies are there. Your job is to have looked at those studies as an applicant for this job.”

It’s not the first time Kennedy has said he’s not “anti-vaccine,” but as a CNN fact check from 2023 noted, despite those claims, Kennedy has been one of the country’s most prominent anti-vaccine activists and has for years used false and misleading claims to undermine public confidence in vaccines that are indeed safe.

Routine childhood vaccinations are projected to prevent hundreds of millions of illnesses, tens of millions of hospitalisations and more than 1 million deaths among people born between 1994 and 2023, according to the CDC.

Vaccines are thoroughly tested before their release, and their safety is monitored on an ongoing basis.

During his confirmation hearings, Kennedy also made several mistakes when describing how Medicare and Medicaid operate, deepening Democrats’ concerns about his ability to lead the massive agency.

As HHS secretary, he will oversee the two programs that provide health insurance to more than 150 million Americans.

At one point, he incorrectly described Medicare Part A as “mainly for primary care or physicians,” when it actually covers inpatient hospital care.

He also skipped over the fact that half of enrollees are in Medicare Advantage plans run by private insurers who are paid by the government to care for beneficiaries.

Plus, he said that Medicare is paid for by employer taxes, leaving out the other funding streams, such as enrollee premiums and government support.

When describing Medicaid, Kennedy said the program is fully funded by the federal government, but it is actually jointly funded by the federal government and states.

And he said costs in Medicaid are too high, though states only charge nominal copays for certain services.

Kennedy launched a presidential bid during the 2024 election cycle – first as a Democratic challenger to then-President Joe Biden, then as an independent – focused on reversing “the chronic disease epidemic.”

He proposed numerous policies aimed to overhaul food safety and environmental guidelines, promote holistic medicines and restructuring public funding for vaccine research.

In the final days of Kennedy’s campaign, he met with Trump on multiple occasions, in which the two discussed the possibility of him endorsing Trump in exchange for a role in his administration. Kennedy later suspended his campaign and endorsed Trump.

The votes to confirm Kennedy, along with Gabbard and Hegseth, underscore the degree to which the Trump White House has been able to keep Republican senators in line throughout the confirmation process, minimising dissent as the administration attempts a historic overhaul of the federal government.

The White House ultimately won over sceptical GOP senators through a mix of Trump’s personal conversations with senators, extensive engagement from Vice President JD Vance – a former senator from Ohio – and assurances from nominees that their past controversial views would not drive their positions in Trump’s Cabinet.

Those closest to Trump have long believed that successfully pushing his nominees through the confirmation process would be a crucial early test of his strength on Capitol Hill, multiple sources familiar with the strategy told CNN.

Sen. Bill Cassidy, a Louisiana Republican and doctor, at one point said that he was “struggling” with Kennedy’s nomination.

But Cassidy later announced he would vote yes, saying that he had what he described as “intense conversations” with the White House and thanking Vance for “honest counsel.”

GOP Sen. Lisa Murkowski of Alaska said Wednesday that she would support RFK Jr.’s confirmation.

Murkowski said, “I continue to have concerns about Mr. Kennedy’s views on vaccines and his selective interpretation of scientific studies, which initially caused my misgivings about his nomination.” But the senator went on to say that Kennedy “has made numerous commitments to me and my colleagues, promising to work with Congress to ensure public access to information and to base vaccine recommendations on data-driven, evidence-based, and medically sound research.”