President Donald Trump hailed Operation Warp Speed as one of his administration’s greatest achievements during a recent Cabinet meeting, even as his pick for Health and Human Services secretary, Robert F. Kennedy Jr., faced intense criticism at a congressional hearing for efforts to restrict access to vaccines, including COVID-19 shots central to the effort Mr. Trump has touted.

The three-hour hearing exposed a contrast between widespread bipartisan praise for the unprecedented federal program to accelerate COVID-19 vaccines and a growing cadre of vaccine-skeptical figures within the president’s political orbit. Kennedy, seated at the Cabinet table while Mr. Trump lauded Operation Warp Speed, was repeatedly challenged Thursday by lawmakers over his past advocacy and policy proposals.

Mr. Trump described Operation Warp Speed as "one of the greatest achievements ever," crediting the program with accelerating development and distribution of COVID-19 vaccines. Democrats on the Senate panel, while critical of Kennedy’s positions, also acknowledged the program’s role in rapidly producing vaccines. Sen. Maggie Hassan, D-N.H., called Operation Warp Speed "a monumental achievement."

Sen. Raphael Warnock, D-Ga., told Kennedy he represented a public health concern and contrasted Kennedy’s stance with the administration’s prior push to speed vaccine development. Lawmakers questioned Kennedy about his history of opposing or seeking to limit access to several vaccines, including the mRNA COVID-19 inoculations that were central to the 2020 effort.

Kennedy’s testimony underscored tensions within parts of the Republican coalition: a willingness to embrace the political and scientific success of Operation Warp Speed alongside growing skepticism of mRNA vaccine technologies among some supporters of the "Make America Great Again" movement. Several senators emphasized that praise for the 2020 vaccine effort crossed party lines even as they criticized Kennedy’s recent work and statements.

Operation Warp Speed, launched by the Trump administration in 2020 amid the COVID-19 pandemic, combined federal funding, regulatory flexibility and private-sector partnerships to accelerate vaccine research, manufacturing and distribution. The program aimed to shorten the typical vaccine development timeline through parallel testing and early production agreements.

The hearing did not resolve broader questions about how the administration will reconcile the president’s public praise for the vaccine program with policy approaches advocated by Kennedy and other vaccine critics. Lawmakers from both parties pressed Kennedy on scientific claims and the potential public-health consequences of policies that could limit access to vaccines that public health officials say are effective at preventing serious illness.

The exchange reflects a larger, ongoing debate about public health, trust in medical institutions and the political dynamics of pandemic-era policy. While Operation Warp Speed remains a frequently cited example of government-led innovation in crisis, the hearing illustrated how divergent views on vaccine science persist among high-profile political figures and their supporters.