People in a Lincolnshire town say they are "in limbo" over when they will get their second Covid jabs, despite waiting over the recommended time.
Government guidance says everyone should be offered a second vaccine dose within 12 weeks of the first jab to be fully vaccinated against the virus.
But Mablethorpe resident Keith Farrow, 75, said his 12-week wait was up on Sunday 18 April and was still waiting.
Health bosses have reassured residents they will get their top-up doses soon.
Mr Farrow said he had been told by his surgery there was a problem with deliveries but he would be notified about a new appointment as soon as possible.
"It's that sitting by the phone every day. We'd just like to know what is happening," he said.
Mr Farrow added that his neighbours had told him they were in a similar position.
Another local resident told the BBC they felt they had been "left in limbo", while others said they were concerned that delays could make them more vulnerable to Covid-19.
'Immunity doesn't just end'
However, Deputy Chief Nurse Rebecca Neno, from NHS Lincolnshire Clinical Commissioning Group (CCG), said there was no need to worry.
"The deliveries of vaccines don't always match exactly to the 12-week interval between vaccinations. Some people get called a few weeks early - some get called a few weeks later," she said.
Ms Neno said she wanted to reassure those who had experienced a "slightly longer" wait that the first dose would still offer them a high level of protection.
"Immunity doesn't just end at 12 weeks," she said.
NHS Lincolnshire CCG said there was "an adequate supply" to cover second dose vaccinations for everyone in Lincolnshire.
A spokesperson for the Department of Health and Social Care (DHSC) said: "Our vaccination programme continues to make phenomenal progress [and] we have been clear everyone who is due a second dose should receive it on schedule."
The DHSC spokesperson added they were also "on track" to offer a first jab to all adults by the end of July.
More than 10 million people in the UK have received a second dose of a Covid-19 vaccine, according to latest government figures, meaning over 19% of UK adults are now fully vaccinated.