Almost 300 fraudulent Covid-19 passport claims have been rejected in Northern Ireland.
The figure emerged after the region’s vaccine certification system was dogged with technical difficulties last week.
It was partially suspended on Tuesday after issues with data sharing emerged.
The new CovidCertNI app enables users to show proof of vaccination for international travel.
Dr Eddie O’Neill, who leads the programme, said on Monday that it is now “stable and running well."
He also revealed that 294 applications where people have fraudulently tried to claim a certificate have been rejected.
“We had three individuals who made 38 applications between them, putting in different vaccination dates every time,” he told the.
The programme has issued 5,843 certificates in less than 28 hours.
“The system is stable, it’s running well, we did everything as we said we would do it, we released it in phases and now people are hopefully feeling a bit less anxious,” he said.
The vaccine certificates are valid for three months once issued.
Those planning to travel on and between August 4-10 can apply via the NI Direct website.
Thirteen Covid-19 deaths were reported in Northern Ireland over the weekend, while 1,072 new cases of the virus were confirmed on Sunday by the Department of Health.
A GP in Northern Ireland has claimed that a "can't be bothered" attitude towards getting a Covid-19 vaccine is contributing to Covid deaths
Speaking to the, Dr Frances O'Hagan, deputy chairwoman of the British Medical Association (BMA) in NI, said some people have an attitude of "I'll get around to it next week or whatever".
"I'm looking towards our numbers of having still over 1,000 cases a day and unfortunately the very sad tale of our 13 deaths over the weekend. That's the product of 'I can't be bothered'."
The latest figures show just 61.4% of those aged 18-29 have received a vaccine, with uptake in other age groups significantly higher.
Dr Tom Black, the BMA's Northern Ireland chairman, told, older people understand what vaccinations are for because they have seen the alternative.
"When I was a young doctor I used to deal with two or three cases of meningitis every week.
"The older folk know if you get your vaccination you don't get meningitis. I think younger folk have to some extent been protected, they haven't had that exposure, that experience of severe illness due to a lack of vaccination.
"There is a lesson to be learned, you need your vaccine to protect yourself. If you don't have it you will be at risk."