WASHINGTON — The leader of Operation Warp Speed says the Trump administration was looking at several different vaccines during the summer when it had the option to lock in additional Pfizer vaccine doses.

Chief science adviser Moncef Slaoui told ABC on Tuesday “no one reasonably would buy more from any one of those vaccines because we didn’t know which one would work and which one would be better than the other.”

The administration is coming under scrutiny for failing to lock in a chance to buy millions of additional Pfizer doses. That decision could delay the delivery of a second batch of U.S. doses until Pfizer fulfills other international contracts.

Assistant Secretary for Health Adm. Brett Giroir says the situation with Pfizer doesn’t change the timeline for vaccinating “any American who wants it” by “late spring and early summer.” He tells CBS, “We will be able to vaccinate about 20 million people this month and another 20 million to 25 million in January and another 20 to 25 million in February.”

Those numbers assume FDA authorization of the Pfizer and Moderna vaccines.