Some doctors in England have complained of delays in receiving doses of the Covid-19 vaccine.
One Kent GP has been forced to cancel 80 vaccination appointments set for tomorrow after a vaccine delivery was postponed.
A GP in Southport, Merseyside cancelled 128 appointments for the same reason.
NHS England says delays are caused when vaccination hubs haven't demonstrated the necessary safety checks, but doctors dispute this.
One GP told the BBC they were told by their Clinical Commissioning Group there was a software glitch with Pinnacle, the IT system used for recording vaccinations. NHS England says there are no reports of technical issues.
Dr Yvette Rean's vaccination site was due to receive 975 doses of the Pfizer-BioNTech vaccine today, but was told yesterday the doses won't be arriving until Tuesday.
"We've had to cancel 80 patients who had all arranged transport. It's chaos and it's not fair on the patients or the GP practices and staff," she said.
I'M GOING TO SHOUT NOW.— Yvette Doc 😷 #WearAMask (@yvettedoc50) December 13, 2020
HAVING SPENT WEEKS ORGANISING THESE COVID VACCINES & GETTING 975 PATIENTS BOOKED IN, WE HAVE BEEN TOLD THEY WON'T BE ARRIVING ON MON AS PLANNED BUT TUES SOMETIME
I HAVE 80 PATIENTS BOOKED FOR TUES am @TeamGP @NHSEngland @NikkiKF @DrSimonHodes @pulsetoday
Adding to the pressure on GPs is the vaccine's short life span once it's been removed from frozen storage. GPs have been told they have just five days from when a batch of vaccines has thawed from -70C, to when the doses must be discarded.
Dr Rean says the delay in getting the batch to the vaccination site in Kent means she'll be left with 3.5 days to carry out nearly 1000 vaccinations.
"We are having to rebook for a full day of vaccinating," she said. "There isn't a central booking system in place, so this is having to be done manually, so it is a logistical nightmare. All this and we are running our GP service at the same time."
A spokesperson for the NHS, said: "Practices will start vaccinating once all the necessary safety checks have been completed, and when surgeries can demonstrate they meet updated guidance."
But Dr Rean said her vaccination team received an email on Saturday from the regional NHS Clinical Commissioning Group, saying the site had been cleared for vaccines to go ahead.
It's been a similarly frustrating experience for Dr Simon Tobin, a GP in Southport, Merseyside. He and his staff spent Sunday lining up vaccination appointments for 128 of the surgery's most vulnerable patients, only to be told the doses would be delivered 24 hours late.
"It was absolutely gutting for myself and the staff," he said.
He tweeted: "I'm just so frustrated after all our hard work today. We'll have to ring them [the patients] ALL again tomorrow."
"So relieved I could cry."
Dr Richard Van Mellaerts, a clinical director of the Kingston Primary Care Network in London, said he had staff working over the weekend in case his batch of vaccines arrived. Late on Sunday he was told the delivery might not arrive until Tuesday.
When the delivery did arrive on Monday morning he tweeted: "I am so relieved I could cry."
Pfizer, which is working with the German firm BioNTech to manufacture the vaccine, confirmed there are no delays at its factory in Belgium, nor in delivering the vaccine doses to UK distribution centres.
A Pfizer spokeswoman told the BBC: "We are working closely with the NHS across all four nations to support the efficient roll-out of the Pfizer/BioNTech COVID 19 vaccine.
"Pfizer is supporting the delivery of the vaccine to the Government's requested locations which is progressing according to plan. The Government and NHS are then handling the onward distribution to vaccination sites."