Sen. Bernie Sanders (I-VT) is calling on Health and Human Services Secretary Robert F. Kennedy Jr. to resign from President Donald Trump’s administration over his vaccine policies, warning that his continued leadership could cause a public health crisis, as reported by Fox News.

“We’ve got to rally the American people. This is a huge issue,” Sanders told Fox News Digital on Monday during a visit to Manchester, New Hampshire, where he headlined the state AFL-CIO’s annual Labor Day breakfast.

Sanders, the ranking member of the Senate’s Health, Education, Labor and Pensions Committee, argued that Kennedy’s long-standing opposition to vaccines and his actions since becoming secretary threaten to undermine decades of public health progress.

“I’m not a scientist, I’m not a doctor, but I do talk to scientists, and I do talk to doctors, and the evidence is overwhelming. It’s not contestable. Vaccines work. They save millions and millions of lives,” Sanders said.

Sanders also warned, “If Kennedy and his friends are able to make people think that vaccines are not safe, it will be a real public health crisis for America.”

Kennedy, a longtime environmental activist and vaccine skeptic, was appointed late last year by President Trump as health secretary in his second administration. Since then, a number of his decisions have drawn scrutiny.

The calls for his resignation intensified after last week’s dismissal of Centers for Disease Control Director Susan Monarez, less than a month after she was confirmed.

Monarez was removed after refusing to carry out Kennedy’s directives to impose new restrictions on the availability of certain vaccines, including COVID-19 shots.

Following her firing, four other top CDC officials resigned in protest, accusing Kennedy and the administration of politicizing public health.

In a weekend opinion piece in the New York Times, Sanders wrote:

“Mr. Kennedy and the rest of the Trump administration tell us, over and over, that they want to Make America Healthy Again. That’s a great slogan. I agree with it. The problem is that since coming into office, President Trump and Mr. Kennedy have done exactly the opposite.”

Sanders further criticized Kennedy’s statements, noting that he has “absurdly claimed that ‘there’s no vaccine that is safe and effective.’” Sanders pointed out that one of Kennedy’s cited experts had his medical license revoked and saw a study retracted from a scientific journal.

The controversy has sparked rare bipartisan concern in Congress, with both Republicans and Democrats questioning Kennedy’s leadership of HHS.

The White House, however, defended the decision to fire Monarez. Press Secretary Karoline Leavitt told reporters Thursday that President Trump has the authority to remove officials who are not aligned with his administration’s goals.

“The president and Secretary Kennedy are committed to restoring trust and transparency and credibility to the CDC by ensuring their leadership and their decisions are more public-facing, more accountable, strengthening our public health system and restoring it to its core mission of protecting Americans from communicable diseases, investing in innovation to prevent, detect and respond to future threats,” Leavitt said.