By Sharon Terlep and Jaewon Kang

As pharmacies and groceries across the U.S. prepare to dispense Covid-19 vaccines to the public, their customers and workers are wondering what happens to extra doses left unused at day's end -- and who might get access to one.

The companies say they are determined that no doses will go to waste, and are compiling wait lists and putting their own workers on standby in case extra shots become available.

Some 6,500 pharmacies in all 50 states -- including those at CVS Health Corp., Walmart Inc. and regional grocers -- will get 1 million doses from the federal government starting Thursday.

There is no charge to receive the vaccine, but the chains require customers who are eligible under state rules to schedule an appointment.

The question of what to do with extra shots can be tricky, though. Doses, which can expire within hours after coming out of cold storage, might go unclaimed if people don't show for appointments, or if vials contain more doses than expected.

Pharmacies face demand from customers and their own employees, and they are subject to a patchwork of state and local rules that may forbid vaccinating those who don't meet current eligibility requirements.

Maintaining wait lists can prove difficult too, as customers can register for more than one list or try to book appointments without meeting state guidelines.

Each state has its own rules for vaccine eligibility, in addition to guidelines from the U.S. Centers for Disease Control and Prevention. In some places, a vaccine provider can be penalized for inoculating a person who doesn't meet eligibility requirements, though generally those rules are relaxed when it comes to finding a use for spare doses that would otherwise expire, according to retailers and state guidelines.

Retail pharmacies are taking varied approaches to extra doses, with some saying they'll give priority to their employees while others say they'll try to find takers among the public and only vaccinate employees as a last resort, if at all. Most companies say they will coordinate with local health officials to ensure additional doses get to the right recipients.

CVS and Walgreens-Boots Alliance Inc., which will be the two biggest retail providers of vaccines, say they already have been vaccinating employees in small numbers with leftover doses that are set to expire and plan to continue as they vaccinate more broadly.

Drugstore employees already qualify for the vaccine under some state guidelines, because they are considered healthcare or front-line workers. But companies say leftover doses, in many cases, can also go to workers who wouldn't otherwise qualify, such as cashiers.

"Bottom line, we're not going to let a dose go to waste," a CVS spokesman said.

Walmart, which plans to administer federally allocated vaccine doses from stores in 22 states, adding to stores in 11 states already administering doses from state supplies, offers doses at risk of spoiling to shoppers or workers who qualify under state guidelines, said a spokeswoman.

"We turn to individuals, including our associates, who fall within that priority to administer the remaining doses. If no one is available in that priority, where states allow, we move to the next priority," she said. In some states, including New York, Illinois, Maryland and New Mexico, retail workers are deemed eligible, she said. In some cases, stores are keeping lists of eligible people to call to give excess doses, said a person familiar with the situation.

CVS, Walgreens, Walmart and Rite Aid Corp. declined to say how many of their workers they have vaccinated so far.

Other retailers are consulting wait lists of eligible customers or announcing spare doses to shoppers inside the store.

"If there were one or two doses left at the end of the day, no one is going to waste that precious resource," said Vic Vercammen, chief pandemic officer at supermarket chain Giant Eagle Inc.

Florida-based Publix Super Markets Inc. said it vaccinates employees ages 65 and older at the end of the night. Midwest chain Hy-Vee Inc. said it gives priority to its wait list of eligible customers but doesn't currently vaccinate its own employees.

Albertsons Cos. contacts eligible customers if there are extras, but supply shortage is a bigger issue right now, said Omer Gajial, senior vice president of pharmacy and health at the grocer. In a single day, the grocer recently booked appointments for all 19,000 doses it received for the state of Washington.

Koninklijke Ahold Delhaize NV, which owns the Giant and Stop & Shop chains, has provided leftover shots to employees, but said it happens rarely.

Recently, a Giant customer received a leftover dose and posted a video of his experience that went viral.

Shoppers began hanging out in stores in hopes of receiving inoculations at the end of the day and that became a significant issue for the grocer, said John McGrath, vice president of pharmacy services at Ahold Delhaize's Retail Business Services.

"That does not help with social distancing," Mr. McGrath said, adding that people stopped lingering after Giant staff told customers that it had no extra doses. Ahold Delhaize's goal is to schedule every vaccination and have appointments queued up, he said.

For some chains, wait lists are already proving difficult. Some customers are putting themselves on multiple online wait lists for extra doses, said Charlie Hartig, CEO of Midwest chain Hartig Drug Stores. For now, people can stay on more than one wait list if they indicate that they are willing to travel for inoculations.

--Sarah Nassauer contributed to this article.

Write to Sharon Terlep at sharon.terlep@wsj.com and Jaewon Kang at jaewon.kang@wsj.com

Corrections and Amplifications

This article was corrected at 1:59 p.m. ET because it misstated that Albertsons booked appointments for all 90,000 doses in Washington state. Albertsons booked appointments for all 19,000 doses in Washington state.

(END) Dow Jones Newswires

02-11-21 0544ET