State and federal officials must ensure providers are equipped to administer a vaccine that needs to be kept at extremely cold temperatures, as one of the leading vaccine candidates would require. States are also missing out on desperately sought federal funding to hire and train staff to administer the shots, as they’re also trying to amass basic supplies. Some states may also rely on a new, untested federally designed system to track who’s getting shots and manage supplies.

“It’s the littlest thing that trips up a whole system,” said Kris Ehresmann, the Minnesota Department of Health’s infectious disease director.

In short, state officials overseeing the largest and most complex vaccination campaign in history say the effort will require a level of careful coordination with the federal government that’s been lacking during the pandemic. Struggles on obtaining testing supplies and protective gear have instilled worries about a smooth vaccination rollout, and a key deadline for states to deliver distribution plans has already been pushed back. A breakdown along any step in the process could cause vaccine distribution efforts to stumble, prolonging the country’s return to normal.