The U.S. government is paying $530 for each five-day course of Paxlovid, Pfizer’s oral COVID-19 treatment. But if one of six other wealthy countries gets a better deal from Pfizer on Paxlovid, the U.S. government’s contract for the first 10 million doses would allow it to secure a lower price.

The six countries mentioned in the “most favored nations” clause of the contract are: Canada, France, Germany, Italy, Japan and the United Kingdom.

The purchase agreement also features a buyback clause. If, for example. Paxlovid’s Emergency Use Authorization gets pulled, Pfizer agrees to buy back unexpired doses. Details of the Paxlovid contract were broadcast by NPR after the network filed a public records request.