But earlier this year the Trump administration decided not to buy an additional 500 million doses of the vaccine.

The Food and Drug Administration announced that Pfizer’s COVID-19 vaccine meets the “success criteria” outlined for an emergency use authorization. The decision moves the vaccine one step closer to full approval and distribution. 

The next step is for an outside panel of experts to review the FDA data on Thursday, and final approval from the agency to begin distribution could come as early as this weekend. 

The good news about the upcoming vaccine comes on the heels of news that the Trump administration declined an opportunity to buy millions of additional doses of the Pfizer vaccine over the summer. The decision could delay the distribution of the second batch of doses until after Pfizer fulfills other contracts with international buyers.

Experts have agreed that the first round of doses will go to medical personnel who have been on the front lines of the pandemic and are at a high risk of contracting the virus because of their work. 

News of the Trump administration’s decision to decline an option to buy as many as five times more doses of the vaccine was confirmed on Monday. The administration agreed to buy 100 million doses of the Pfizer vaccine, enough to vaccinate 50 million Americans. However they declined an offer to buy an additional 500 million more doses. 

Pfizer is not the only vaccine manufacturer close to the finish line. Drugmaker Moderna is also on track to receive emergency use authorization from the FDA later this month. After news broke of Trump’s decision not to buy more Pfizer vaccines, his administration insisted late Monday that between the two vaccines the country will be able to vaccinate every American who wants to be vaccinated by the end of the second quarter next year. That ambitious deadline would mean every American interested in the vaccine would receive it by the end of June. 

The White House is planning a vaccine summit Tuesday to address skepticism over the vaccine and highlight plans to distribute the vaccine. However, neither drug maker has accepted the invitation to attend and President-elect Joe Biden, who will oversee the majority of the largest vaccination process in history, was not invited. 

Instead, the summit will feature Vice President Mike Pence, government experts, state leaders and business executives. 

Biden said last week that “there is no detailed plan that we’ve seen,” on the details of distributing and administering the vaccines. The Trump administration has insisted that the bulk of that logistical work will need to be addressed by state and local governments. 

The Trump administration’s refusal to outline guidelines for states poses an additional problem for distribution, because the two vaccines come with unique challenges. For instance, the Pfizer vaccine must be transported at extremely low temperatures and comes in batches of nearly 1,000 vials. Each vial contains five doses, which means every step of the way requires careful planning. If a misstep happens, valuable vaccines could be rendered useless. 

The Associated Press contributed to this report.