Pfizer, which is a for-profit company, has been making its own case for booster shots. Last month, the company reported that the power of its two-dose vaccine wanes slightly over time, but continues to offer lasting protection against serious disease. “It’s in their interest to say third doses are required,” Apoorva says.

It’s also more profitable to sell vaccine doses to countries like the U.S., which pay more money for the shots than poorer countries could. Pfizer and Moderna both recently increased the price of their vaccines in new contracts with the E.U.

There’s also some anecdotal evidence of people getting third shots in the U.S., even though the government doesn’t recommend it at the moment. (One San Francisco hospital is offering a supplemental shot to residents who got the one-dose Johnson & Johnson vaccine.)

“I see it on social media all the time: people saying, ‘I was worried so I just went to the CVS and got a third dose,’” Apoorva told me. But, she added, right now there’s no need — so far the “evidence tells us it is not necessary.”