The Biden administration on Thursday took a modest first step toward sharing coronavirus vaccines with the world, announcing that it intends to send 1.5 million AstraZeneca doses to Canada and 2.5 million to Mexico.

Why it matters: The vaccine developed by AstraZeneca and Oxford University hasn't been approved in the U.S., and the White House has faced growing criticism for sitting on doses that could be used elsewhere

• The deal comes in the form of a loan, with the U.S. sending doses to Canada and Mexico now with the expectation that they will return doses to the U.S. later this year.

The big picture: The world has four major sources of coronavirus vaccines: China (33% of all doses produced), the U.S. (27%), the EU (19%) and India (13%), according to data shared with Axios by Airfinity, a science information and analytics company.

• While China has exported around 60% of the vaccines it has produced — in part due to a low sense of urgency in China, where the virus is largely under control — the U.S. has exported 0%, focusing instead on covering all U.S. adults.
• India has exported 65% of its production to date, per Airfinity, but the CEO of the country's largest producer said last month that he'd been "directed to prioritize the huge needs of India."
• The EU is having a vigorous debate about whether to more tightly control exports, lamenting what it sees as an imbalance with the U.S. and U.K.