A nurse is worried she was lured into a false sense of security regarding the vaccine after she caught coronavirus only a matter of weeks after receiving the Pfizer vaccine.
The NHS employee, who wishes to remain anonymous, works within the Hywel Dda University Health Board area in south-west Wales, which covers Pembrokeshire Local, Ceredigion and Carmarthenshire.
She's said of her new positive test result that she is "angry and heartbroken" that she's caught the deadly virus at this stage.
Wales is also in a tight lockdown, with First Minister Mark Drakeford set to review the measures next week as the UK continues to report staggering death figures.
The new mutant strain of Covid has been ripping across Britain, and the nurse in question explained she was initially relieved to be offered the chance of the vaccine back in December when the new, highly contagious strain emerged.
At first, she had trouble getting an appointment, however, she managed to receive her first dose of the Pfizer-BioNtech vaccine just over three weeks ago.
The hospital nurse, who works in the Hywel Dda University Health Board area in west Wales, said she felt "angry and heartbroken" about catching Covid at this stage.
She added: "It gave me peace of mind. It made me feel safer and that I was doing the right thing for my family, but it gives a false sense of security."
The nurse also explained that she was told it would take 10 days for the jab to offer her some protection against the virus and reduce risk of transmission, however, she started feeling unwell three weeks later.
Her partner and one of her children has also tested positive, experiencing "quite severe symptoms" of a high temperature, breathlessness and a bad cough.
She added she was "shocked" when she found out she had contracted the virus.
The Pfizer vaccine was the first to be rolled out and began on December 8 2020.
Two doses are needed for the vaccine to work fully, and currently, around a million people have had their first dose.
Advice regarding the vaccine for the whole of the UK was that the second dose of the vaccine was needed three weeks after the initial one, however, this has since changed.
Now, it's recommended that there is a 12-week gap between doses, following the UK's chief medical officers' advice.
The World Health Organisation has stated that it does not recommend following the UK's decision but has "made a provision for countries in exceptional circumstances of vaccine supply constraints and epidemiological settings" to delay the second dose for a few weeks, as this will maximise the number of people getting their first dose.