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 this morning 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 BBC.
However he said 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 between 4 and 10 August can apply via the NI Direct website.
Meanwhile, from today new changes to international travel mean passengers from EU amber list countries and the US who have had two jabs no longer have to self isolate upon arrival in Northern Ireland.
This brings Northern Ireland into line with policy across the UK.