Before COVID, Moderna was a startup which had never brought a therapy to market. They've managed to stay independent, instead of a marriage to one of the giants like BioNTech has. As such, Moderna's production capacity was almost entirely funded by the US via OWS contracts - so until those orders are fulfilled, almost all Moderna doses have to go to the US, and even after that Pfizer has much larger global production capacity.

Seems like it it very common in the Mountain West region. Especially at the start, it seemed like far more Moderna than Pfizer. Now it seems about equal.

Not OP, just to clarify for US folks: Here in the EU Moderna is only small part of the vaccination effort. The breakdown so far is roughly 70% Pfizer/Biontech, 20% AstraZenca and 10% Moderna. The Moderna deliveries are supposed to increase in Q3, however I am not sure how relevant it will be at that point. The EU also finalized a deal for 1.8 billion Pfizer/Biontech shots for the next couple years. So Moderna will probably also not be super relevant here going forward.

Is there so little supply? I thought there was a glut of vaccines in the US. I just got my second dose of Moderna yesterday (in the US South), and there was nobody at the vaccine center.

I should perhaps noted that I was speaking from an EU perspective. The US seems to be doing great, I wish I could say that we are as well.

I see a lot of Moderna vaccine appointments in MA. Maybe they don't have the scale like Pfizer and most of their supply is staying in MA?

Nope, I got Moderna weeks ago on Staten Island, NYC.