Appointments are being canceled, sites are temporarily closing, county waitlists are in the thousands and states are adjusting eligibility timelines as vaccines supplies dwindle nationwide.
With shipments coming weekly, officials say they don't have much visibility on their supplies as they simultaneously schedule first and second doses, and plan to expand vaccination sites.
"There's a lot of uncertainty right now," Dr. Amesh Adalja, a senior scholar with Johns Hopkins Center for Health Security, told ABC News. "Everybody knows that the supply chain will be coming, but nobody knows exactly when it is coming, how much of it is coming and how steady the supply chain will be. That makes it harder to plan."
With its current supply on track to be depleted by the end of this week, and a shipment of over 100,000 Moderna vaccines delayed, the New York City health department will close 15 vaccination hubs from Thursday through Sunday, officials said.
"This is crazy," Mayor Bill de Blasio said during a media briefing this week. "This is not the way it should be. We have the ability to vaccinate a huge number of people. We need the vaccine to go with it."
Some 23,000 people expecting to receive their first dose will need to reschedule, de Blasio said Wednesday.
New York City isn't alone. San Francisco Mayor London Breed said Tuesday that the city is projected to run out of vaccines by Thursday if more don't arrive.
"We simply need more vaccines," said Breed, noting that the city had set up a new dashboard to track vaccine allotment.
As Collin County, Texas, waits for more shipments, more than 144,000 people are currently on its vaccination waitlist. Just over 1,000 doses have been administered, and 7,000 new doses were expected this week.
Residents are frustrated.
"I don't want to die of COVID. It's that simple," Plano resident Pat Parker, who said she is no. 16,793 on the waitlist, told ABC News Dallas affiliate WFAA-TV. "What did I just register for? Nothing, nothing."
The supply concerns come as many regions are expanding vaccination eligibility. On Wednesday, Los Angeles County opened it up to residents ages 65 and up -- a group that includes over 1 million people -- though local health officials warned that supply remains scarce. Call centers were inundated, and websites crashed as residents attempted to schedule the limited number of available appointments.
"One of the issues that everyone has had around the allocation and distribution from the federal government is it has been week-to-week, which makes it difficult for our sites to do a lot of planning, and it really makes it difficult to extend appointments past a few days, which I think then makes it hard on the public," LA County Department of Public Health Director Dr. Barbara Ferrer said Tuesday at a media briefing.
States also have had to adjust their timelines after learning late last week that they wouldn't receive as many doses as anticipated from the federal reserve. Oregon health officials said they would have to delay the expansion of doses to seniors by several weeks. Instead of starting to vaccinate all seniors on Jan. 23, the state will begin vaccinating in waves, starting with those age 80 and older on Feb. 8.
"The approach completely depends on Oregon getting a reliable supply of doses from the federal government," Patrick Allen, director of the Oregon Health Authority, said during a press briefing Friday.
The certainty around the federal supply is making it difficult to open more vaccination sites and plan more than a few weeks out, health officials in Mississippi said.
"We don't know where we're going to be in a month," Dr. Thomas Dobbs, the state health officer, said Friday during a panel with the Mississippi State Medical Association. "Since we don't have 100% visibility of the vaccine on hand for a week from now, it's too far ahead of us to plan properly."
This lack of visibility led to some confusion last week, when the state health department announced new vaccine appointments wouldn't be available for a month out. After additional supplies became available, residents are now able to make appointments as early as Jan. 25, officials said.
"We can't depend on much stability," said Dobbs, noting he expects the situation to improve in the coming weeks.
As New York City runs out of available first doses, de Blasio floated freeing up the second doses the city has on reserve.
"We've got about 65,000 doses that we could put into play right away if we had that freedom," he said. "Let's be creative and let's do something to reach the most people as quickly as possible -- and then catch up in the days ahead."
With a new administration in the White House, many leaders are hoping for more transparency on available doses and ramped-up production of the Pfizer's and Moderna's vaccines. Other COVID-19 vaccine candidates, such as Johnson & Johnson's, also could help with supply shortages if authorized, health officials said.
"I know the Biden administration is going to intensify production," de Blasio said. "I have faith that the weeks ahead, we're going to see a whole different level of production of the vaccine happening."
Ferrer urged patience, saying that with a new federal administration, "We expect our situation to improve greatly."
For now, Adalja recommended that people continue to be "tenacious" about getting appointments if they're eligible, as the longer people go unvaccinated, the more time the virus has to spread.
"It's unfortunate that it's come to this," he said. "It shouldn't be this hard to get a vaccine."