The Trump administration turned down the chance to secure more of the Pfizer-BioNTech coronavirus vaccine, which Britain became the first to roll out Tuesday, and will probably need to wait until June or July to procure doses beyond an initial order of 100 million because other countries have snapped up limited supply, the company told the White House.

Trump administration officials defended their decision, noting that the United States is at the front of the line for the promising Moderna vaccine, which is expected to be approved in coming weeks, along with the Pfizer jab. But both vaccines require two doses, meaning the 100 million doses purchased of each will cover two sets of 50 million people — far short of the entire population.

The European Union and Japan have both staked claim to an even larger portion of Pfizer doses than the United States has, and Americans will have to wait as those countries receive shares of their initial orders while supplies remain limited. But as a wealthy country with a large number of orders in place and good cold storage infrastructure, the United States is still near the top of the global vaccine pecking order, while some poor countries could have to wait until 2024 to offer vaccines to their entire populations, according to one study.

Given the Trump administration’s big promises on vaccines, the prospect of limited supply and long waits in the United States will lead to questions about where those doses are going. Here is what we know so far.

On Dec. 8, Margaret Keenan, 90, and William Shakespeare, 81, became the first British patients to receive the Pfizer-BioNTech coronavirus vaccine shot. (Reuters)

Britain

On Tuesday, 90-year-old British grandmother Margaret Keenan became the first recipient of the Pfizer vaccine outside trials.

The British government has agreed to purchase 40 million doses for delivery in 2020 and 2021.

It is still not clear how much supply will be available in the early months of the vaccination push.

Canada

Canadian Prime Minister Justin Trudeau announced that Canadians will begin receiving the Pfizer vaccine next week.

Canada is set to receive up to 249,000 doses this month, according to the government, though use will be contingent on Health Canada authorization of the vaccine.

The initial doses will serve as a “dry run” for a larger-scale rollout, allowing Canada to test out the logistics of distributing a vaccine that requires extreme cold storage.

Canada has purchased 20 million doses, with the option to buy 76 million, according to Pfizer.

Japan

In July, the government of Japan announced a major deal with Pfizer: 120 million doses of the vaccine, to be delivered in the first half of 2021.

Pfizer began conducting a small-scale trial in Japan in October. The results of that trial, as well as global results, will shape when the company applies for regulatory approval in Japan, according to Nikkei Asia.

Japan’s vaccine timeline is particularly tight because the country is set to host the Summer Olympics. It is still not clear how much of the 120 million dose order Pfizer can deliver before then.

European Union

So far, the EU has placed the largest order for the Pfizer vaccine: 200 million doses, with an option to buy 100 million more.

E.U. regulators are reviewing the safety and efficacy of the vaccine and could grant authorization before the end of the month.

However, European officials have provided few details about when, where and how the vaccine will eventually be rolled out.

Israel

The first doses of the Pfizer vaccine will arrive in Israel on Thursday, reports the Times of Israel, citing multiple Hebrew media reports.

Israel expects 100,000 initial doses as part of a pilot program to help the country sort out how to store and ship a vaccine that must be stored at minus-94 degrees Fahrenheit and be used within five days of removal from cold storage.

The country reportedly purchased 8 million doses of Pfizer’s coronavirus vaccine.

Others

According to data compiled by researchers at Duke University, Peru, Costa Rica, Ecuador, New Zealand, Australia, Chile, Kuwait and Lebanon have also cut deals with Pfizer.