(Bloomberg) -- Americans looking for the latest Covid jab are being turned away from pharmacies that don’t have enough shots — putting the first week of the new booster rollout off to a bumpy start.

Last week, the Centers for Disease Control and Prevention encouraged all Americans ages 6 months and up to roll up their sleeves for newly updated shots from Moderna Inc. and Pfizer Inc. that have been formulated to protect against newer strains of the virus. But many looking to follow the CDC’s advice have been met with an unexpected obstacle: At some pharmacies, there are still no shots to be had.

A spokesperson for Rite Aid said that manufacturers are experiencing delays in shipping. CVS Health Inc. and Walgreens Boots Alliance also said some stores have yet to receive vaccines.

People all over the US have taken to social media to express frustrations as pharmacies have issued last-minute cancellations or rescheduled appointments for when supply is expected to be in stock. Cynthia Cox, a vice president of KFF, said on Twitter that none of the in-network pharmacies her insurance plan covers had the vaccine in stock yet. Other users said they scheduled appointments at CVS or Walgreens, only to have them canceled due to lack of supply.

The pharmacies said they expect to make more appointments available as supply ramps up, but didn’t provide details on how many stores or appointments had been affected.

“This rollout seems to be especially complicated because now pharmacies are on the hook for purchasing vaccines (as opposed to the government supply),” said Andie Pivarunas, senior director of public affairs at the National Community Pharmacists Association. But, she said, a certain amount of delay is par for course when rolling out a new shot. 

Local health clinics that expected to get vaccines have also had to cancel appointments due to lack of supply. The Carver County Health Department in Minnesota said it had to cancel a vaccine clinic scheduled for Tuesday.  Future dates only list Moderna’s vaccine as an option. Another clinic in Missouri said it had to cancel all vaccination appointments because the vaccines likely won’t arrive until October.

Moderna and Pfizer said they began shipping vaccine doses to wholesalers and retailers immediately after authorization.  A spokesperson for Moderna said its already shipped millions of doses to pharmacies, and that shipments are arriving daily. 

“We expect it to be widely available at pharmacies and prescriber’s offices throughout the US, including places it may not be currently available today,” Jerica Pitts, a spokeswoman for Pfizer, said in a statement. “Insured individuals will continue to receive the vaccine when their local pharmacy or prescriber has supply of the vaccine.”Pfizer said it is not facing a shortage of its vaccine. Neither company could account for why the supply issues are occurring. 

“We now ship to distributors, and they provide to pharmacies and other points of care,” said Chris Ridley, a spokesman for Moderna.The supply snags aren’t necessarily the result of high-demand, as was seen earlier in the pandemic. Pfizer is only forecasting 24% of eligible Americans will get its new booster, up slightly from 17% uptake seen last season. But this time around, there are new variables at play. Before the Covid public health emergency ended in May, the US government paid for vaccines and allocated them to states, essentially streamlining the process. Now, consumers, retailers, distributors and insurers are for the first time navigating booster rollout in the commercial market. 

“It always was anticipated that it could take several weeks for manufacturers, distributors and pharmaceutical wholesalers to ship the initial and subsequent provider orders,” said Logan Anderson, a spokesman for the Virginia Department of Health.

Many pharmacies, however, began offering booster appointments as soon as the CDC greenlit the new shots last week. They anticipated to have them available within days. 

--With assistance from Nacha Cattan.

©2023 Bloomberg L.P.