The Trump administration has blamed the agency for the coronavirus pandemic.

The U.S. and China have both declined to join a 172-country effort to develop, manufacture and equitably distribute a vaccine for COVID-19.

The decision undermines the global effort to collaborate on a vaccine by encouraging others to fend for themselves first, according to public health experts, and risks Americans not getting access to a successful vaccine developed by another country.

For the Trump administration, opposition stems from the involvement of the World Health Organization, which President Donald Trump and other U.S. officials have blamed for the novel coronavirus pandemic. The U.S. began the withdrawal process from the global agency in July.

Along with the vaccine alliance Gavi and the Coalition for Epidemic Preparedness Innovations, WHO is helping to coordinate the new vaccine effort, known as COVAX, and urging countries to join.

With nine vaccine candidates, under development by pharmaceutical companies and universities, COVAX aims to deliver safe, effective vaccines once they have first received approval to all participating countries equally based on their populations. The project will prioritize healthcare workers, then vulnerable groups like the elderly and those with pre-existing conditions, before distributing further doses based on countries’ individual needs.

“This cannot be a race with a few winners, and the COVAX Facility is an important part of the solution — making sure all countries can benefit from access to the world’s largest portfolio of candidates and fair and equitable distribution of vaccine doses,” said Stefan Löfven, Sweden’s prime minister.

So far, 80 countries have signed up as “potentially self-financing” partners, with 92 low- and middle-income countries that would receive support and increase their purchasing power by working together.

By the end of 2021, the goal is to deliver two billion vaccines globally, COVAX said Tuesday.

But that will require greater coordination and financial contributions — at least $1 billion more for research and development, WHO said Tuesday — and for now at least, it will not include support from the U.S. and China.

Secretary of State Mike Pompeo said Wednesday that “no nation will match” the U.S. commitment to delivering vaccines around the world, “But it is also imperative that when we do that, we need to go do so in a way that’s effective, not political, that is science-based — when we have seen demonstrated from the World Health Organization that it is not that.”

The charge that WHO is political and not science-based is not a new one from Pompeo, although critics say it is gratuitous at best. While WHO was slow to determine the novel coronavirus was contagious, it is limited in its ability to demand information from member states like China. Either way, its work on vaccines has been praised, including by Pompeo earlier this year.

A White House spokesperson went further than Pompeo, seeming to suggest that the U.S. wants to focus on its own production first.

“The United States will continue to engage our international partners to ensure we defeat this virus, but we will not be constrained by multilateral organizations influenced by the corrupt World Health Organization and China,” deputy spokesperson Judd Deere told the Washington Post, which first reported the U.S. decision.

That notion may have some support among the U.S. public, but it has been cast as short-sighted by public health experts, who say it puts Americans at risk.

“Joining Covax is a simple measure to guarantee U.S. access to a vaccine — no matter who develops it first. This go-it-alone approach leaves America at risk of not getting a vaccine,” said Rep. Ami Bera, D-Calif., a doctor and vice chair of the House Committee on Science, Space, and Technology.