The Biden administration will reengage with the World Health Organization and opt into a multilateral effort to distribute vaccines around the world, reversing two decisions by the Trump administration that ripped the country away from public health diplomacy in the middle of a pandemic.

Biden signed a series of directives hours after taking office, including a call to halt the country’s withdrawal from the U.N. health agency. Secretary of State-designate Tony Blinken said in his confirmation hearing Tuesday that the United States will participate in Covax, an international effort to source and distribute vaccines.

By moving quickly on both issues, the incoming administration signaled a return to a more cooperative approach to global health amid a crisis that has already claimed more than 2 million lives worldwide. But after months of WHO-bashing, threats and domestic chaos, America’s future role and influence remain an open question.

Biden’s ability to reenter the coronavirus fight is therefore seen as one early test of his ability to reengage with the rest of the world after four years of “America First” foreign policy.

There is no question that the WHO will continue to work with the United States, its largest donor, experts said. But it remains to be seen whether the appetite for U.S. leadership remains the same.

“I think it’s mixed emotions,” said J. Stephen Morrison, director of the Global Health Policy Center at the Center for Strategic and International Studies.

“The WHO is going to welcome them,” he said. “But there’s going to be an edge to it.”

The start of a new U.S. administration comes at a make-or-break moment for the Geneva-based agency — and for health diplomacy more broadly.

Over the past year, the coronavirus pandemic has tested the multilateral order, particularly the WHO, which has found itself at the center of a global health crisis and a geopolitical storm over China’s role in the international system.

The early days of the Biden administration will coincide with annual WHO meetings. To signal U.S. support, Biden will send a delegation led by top infectious-disease expert Anthony S. Fauci, who is expected to deliver remarks on Thursday.

Fauci’s address will come days after an independent panel published an early review that raised questions about the WHO’s ability to respond to emergencies and amid a months-long debate about reforming the organization.

With the United States on the sidelines, the conversation about WHO reform has been led by other powers, most notably Germany and France.

Blinken said Tuesday that the WHO is an “imperfect” institution in need of reform, but did not offer specifics.

The current debate centers on what went wrong with the coronavirus response and what should be changed ahead of the next emerging health threat.

It is clear now that in the early days of the outbreak, Chinese officials withheld information from the WHO. Unable or unwilling to press for more details, the agency repeated false claims from the Chinese government about the virus’s transmissibility.

In the weeks that followed, WHO officials continued to lavish China with praise, eroding the agency’s credibility, just when it needed it most.

The independent assessment released this week questioned why the agency waited until the third week of January 2020 to hold an emergency session, delayed the declaration of a Public Health Emergency of International Concern, or PHEIC, and was slow to use the word “pandemic.”

“The global pandemic alert system is not fit for purpose,” the panel concluded. “The World Health Organization has been underpowered to do the job.”

Though former president Donald Trump first praised China and the WHO for their handling of the initial outbreak, he later seized on criticism of the Geneva-based agency, using its early missteps to deflect from the crisis unfolding in the United States.

By spring, Trump was threatening to cut funding. In July, he sent a letter giving the agency one-year notice of U.S. intent to withdraw. Though it was never clear whether the United States could withdraw without Congressional approval, the move undermined the agency in the middle of an emergency.

Because the United States had not technically left the organization, it will not “rejoin” this week but instead recommit. A key question going forward is whether reengagement will come with additional financial backing, or other shows of support.

Biden’s team is also expected to opt into Covax. In September, the Trump administration declined to participate in the program because of its link to the WHO. The United States and Russia were the only big players who opted out.

The Biden administration will change that. “We believe strongly that we can ensure that every American gets the vaccine, but also help make sure that others around the world who want it have access to it,” Blinken said Tuesday.

The WHO has stressed that Covax needs more money to reach its goal of vaccinating a significant portion of the population in every country by the end of 2021 — a goal that seems increasingly out of reach.

Those who support the initiative hope the United States will step in with funding, though neither Biden or Blinken has outlined specific plans to date.