Tickets to two HSE and NHS staff only concerts in Dublin with The Script sold out in half an hour.
The free gigs had been announced for the 3Arena in February next year.
The first concert announced was sold out within three minutes, while a second was added.
The band say they are overwhelmed by the response and say it's the least they can do to thank frontline workers for all they're doing to fight Covid-19.
"Myself, Mark and Glen are overwhelmed by the phenomenal response we’ve had to the free shows for HSE and NHS (NI) staff and feel it's the very least we can do to say an enormous and heartfelt thanks to their continued efforts in the fight against this virus," said the band's singer Danny O'Donoghue.
Ticket applications were only available to the eligible frontline staff who must bring their valid staff ID card - original format, no photocopies - to the show, a spokesperson for promoter MCD said.