A British nurse has caught COVID-19 three weeks after getting the vaccine, prompting experts to issue warnings that it would take time for immunity to build up.
The nurse, who has been working for the Hywel Dda University Health Board area in west Wales, said that she got the virus while waiting for the second dose of the Pfizer-BioNtech jab, which was first rolled out in the UK last month.
She said she was “angry and heartbroken” about catching the fatal disease at this stage.
"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," she said.
The nurse, who asked not to be identified, said she was told it would take 10 days for the vaccine to offer some protection, however, she started feeling unwell three weeks later.
She said she had "quite severe symptoms" of a bad cough, high temperature and breathlessness and that was shocked when tested positive.
Meanwhile, Deputy Chief Executive of Hywel Dda health board, Dr Philip Kloer, said that although a COVID vaccine “reduces your chance of suffering” from the virus, no vaccine is ever 100% effectual.
On Friday, the Welsh First Minister warned people receiving the vaccine to “continue to act in a precautionary way.”
Professor Tim Spector, who heads up the ZOE Symptom Tracker App study, has also said that some junior NHS staff members contracted the virus after getting the shot.
"We are getting reports of reinfections, some soon after vaccination, "I'm a junior doctor and have had Covid twice the last one five days post vaccination..."', he wrote on Twitter.
"Remember vaccinations take several weeks to have a preventive effect so keep alert and keep logging!"
This comes after a 56-year-old American doctor in South Florida died two weeks after getting a first dose of a Pfizer vaccine.
Dr. Gregory Michael, a Miami-Beach obstetrician, was in good health, the Sun-Sentinel reported. He received his first dose of the Pfizer-BioNTech vaccine on December 18 at Mount Sinai Medical Center.
However, small spots began to appear on his feet and hands after three days and he went to the emergency room at Mount Sinai, where he had worked in private practice for 15 years.
Michael’s blood count was far below normal ranges, and he was admitted to the intensive care unit. Doctors tried for two weeks but could not raise his platelet count.
The doctor was “conscious and energetic” through the process, but just days before a last resort surgery, he suffered a stroke and died.
Health officials from Florida and the Centers from Disease Control and Prevention (CDC) are investigating whether the vaccine played a role in his death, which possibly is the country's first death linked to the vaccine.
Also, a California nurse tested positive for the coronavirus more than a week after receiving Pfizer vaccine.
Matthew W., 45, who works at two different local hospitals, said in a Facebook post on December 18 that he had received the vaccine.
He told the ABC News affiliate that except for his arm that was sore for a day he had suffered no other side-effects.
However, six days later on Christmas Eve, he got sick after working a shift in the COVID-19 unit. He got the chills and later came down with muscle aches and fatigue.
He then went for a test to find that he was infected with the COVID-19 virus the day after Christmas.