FILE - In this July 27, 2020 photo, a nurse prepares a syringe during a study of a possible COVID-19 vaccine in Binghamton, N.Y.
FILE - In this July 27, 2020, photo, a nurse prepares a syringe during a study of a possible COVID-19 vaccine in Binghamton, N.Y.

WASHINGTON - The Trump administration opted last summer not to lock in a chance to buy millions of additional doses of one of the leading coronavirus vaccine contenders, a decision that could delay the delivery of a second batch of doses until manufacturer Pfizer fulfills other international contracts. 

The revelation, confirmed Monday by people familiar with the matter, came a day before President Donald Trump aimed to take credit for the speedy development of forthcoming coronavirus vaccines at a White House summit Tuesday. 

Pfizer's vaccine is expected to be endorsed by a panel of Food and Drug Administration advisers as soon as this week, with delivery of 100 million doses — enough for 50 million Americans — expected in coming months.  

Under its contract with Pfizer, the Trump administration committed to buy an initial 100 million doses, with an option to purchase as many as five times more.  

This summer, the White House opted not to lock in an additional 100 million doses for delivery in the second quarter of 2021, according to people who spoke about the matter on condition of anonymity because they were not authorized to discuss it publicly.  

FILE - A customer wearing a mask walks out of a Walgreen's pharmacy store and past a sign advising that COVID-19 vaccines are not available there yet during the coronavirus outbreak, December 2, 2020.

Days ahead of the vaccine's expected approval, the administration is reversing course, but it is not clear that Pfizer, which has since made commitments to other countries, will be able to meet the latest request on the same timeline. 

The Pfizer vaccine is one of two on track for emergency FDA authorization this month, the other coming from drugmaker Moderna. 

The Trump administration insisted late Monday that between those two vaccines and others in the pipeline, the U.S. will be able to accommodate any American who wants to be vaccinated by the end of the second quarter of 2021. 

The administration's decision not to lock in additional Pfizer purchases last summer was first reported by The New York Times. Health and Human Services Secretary Alex Azar told NBC the administration is "continuing to work across manufacturers to expand the availability of releasable, of FDA-approved vaccine as quickly as possible. … We do still have that option for an additional 500 million doses." 

Seeking to tamp down public skepticism over the vaccine and secure a key component of Trump's legacy, Tuesday's summit will highlight the administration's plans to distribute and administer the vaccine.  

But officials from President-elect Joe Biden's transition team, which will oversee the bulk of the largest vaccination program in the nation's history once he takes office January 20, were not invited. 

Officials from the pharmaceutical companies developing the vaccines also were not expected to attend, despite receiving invitations, according to people familiar with the matter. Some expressed concerns about the event contributing to the politicization of the vaccine development process and potentially further inhibiting public confidence in the drugs. 

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