Oregon Sen. Ron Wyden, the top Democrat on the Senate Finance Committee and its incoming chair, is launching an investigation into Health and Human Services Secretary Robert F. Kennedy Jr., alleging he lied to Congress during his 2025 confirmation hearing.

In a letter co-signed by Maryland Sen. Angela Alsobrooks, Wyden asks for all documents related to Kennedy's 2019 trip to Samoa, his presidential campaign, his confirmation process, and communications between federal health officials and Children's Health Defense, the anti-vaccine group Kennedy chaired until December 2024.

Children's Health Defense has a December 4 deadline to comply.

The inquiry strikes at sworn testimony from the man who now runs the nation's health agencies. Kennedy testified at his January 2025 confirmation hearing that his June 2019 visit to Samoa had nothing to do with vaccines.

Yet letters obtained by The Guardian and The Associated Press through an open records lawsuit show he wrote to Samoa's prime minister in January 2019 explicitly asking to study what happened with the MMR vaccines, using the words vaccine or vaccination eight times.

HHS has called any claim that Kennedy lied under oath false and outright defamatory, and has not explained why his testimony contradicts the letter.

The trip occurred months before one of the deadliest measles outbreaks in recent history. Samoa had paused vaccinations in 2018 after two children died from improperly mixed MMR vaccines; the administering nurses were charged with manslaughter.

Immunization rates plummeted before the outbreak began in September 2019, ultimately reaching 5,700 cases and 83 deaths, mostly children under five.

Critics, including Samoan officials, say Kennedy's presence as Children's Health Defense chair emboldened anti-vaccine activists and worsened the vaccination crisis. Kennedy denies this, saying he never made a public statement about vaccines or discouraged Samoans from getting vaccinated.

Wyden is expected to assume the Finance Committee chairmanship when Democrats take Senate majority control in January, and he posted a single word — Subpoenas — on election night.

The letter carries no subpoena power yet, but Tim Stretton of the Project on Government Oversight told The Guardian that Children's Health Defense would be unwise to ignore it, since noncompliance could trigger subpoenas.

Knowingly giving false testimony to Congress is a crime, though it is rarely prosecuted; Republican senators led by Rand Paul this year recommended the Justice Department prosecute Anthony Fauci for false Covid-19 testimony.

The probe is one of a broad array of investigations Democrats plan into the Trump administration after regaining control of Congress in the midterms.

Several Democrats, including incoming senator Annie Andrews, a South Carolina pediatrician, have called for Kennedy's impeachment, and Bernie Sanders, incoming chair of the health committee, told The Guardian he is open to it.

Legal experts note the Justice Department under Trump is unlikely to prosecute, but Kennedy's statements could ground hearings, an impeachment inquiry, or other obstacles for the administration. HHS and Children's Health Defense did not immediately respond to requests for comment.