Federal and state governments must increase the number of healthcare workers qualified to administer vaccine doses in order to achieve the widespread immunity needed to end the pandemic, public health experts say, or else millions of shots could go to waste.

“In a few months from now, I do suspect that we’ll be able to vaccinate a couple million people per day, but … we have to have the personnel,” said Dr. Eric Toner, chief scientist at Johns Hopkins University’s Center for Health Security. “Doing it in the hospitals has been the easy part. It’ll get more complicated when we open up the mass vaccination clinics.”