Dr. Walensky’s decision was a boost for President Biden’s campaign to give a broad segment of Americans access to boosters. The White House had come under criticism for getting ahead of the regulatory process.

The White House could begin promoting and rolling out a plan for booster shots as soon as Friday. That would be in keeping with the administration’s previously announced plan to offer the additional doses this week.

The C.D.C.’s statement arrived well past midnight, a sign of the complicated and confusing decision-making surrounding the boosters. The C.D.C. advisers similarly spent two days debating who should get boosters and when, and could not agree on whether occupational risk should qualify as a criterion.

“I am surprised that Dr. Walensky overturned one of the four A.C.I.P. votes today, and I believe others will be as well,” said Dr. Yvonne Maldonado, an infectious disease expert at Stanford and the American Academy of Pediatrics liaison to the committee.