But in a statement on U2's website, Bono said a doctor has ruled out anything serious related to his voice and told fans he will be back for the rest of the group's tour.
Entitled "Back On Song, Back To Berlin", his message reads: "I've seen a great doctor and with his care I'll be back to full voice for the rest of the tour.
"So happy and relieved that anything serious has been ruled out.
"My relief is tempered by the knowledge that the Berlin audience were so inconvenienced.
"There was an amazing atmosphere in the house, it was going to be one of those unforgettable nights but not for this reason...
"We can't wait to get back there on November 13th."
The message was accompanied by a sketch and a picture of a handwritten note which said: "PS To the ones who sang Red Flag Day for me last night, thanks, those are some high notes in that one... as always, 'you take us higher'."
U2 opened the European segment of its 2018 Experience + Innocence tour in Berlin on Friday.
It has a sold-out show scheduled in Cologne on Tuesday and a second concert in the German city on Wednesday before back-to-back performances in Paris on Saturday and Sunday.
Source : Sky Entertainment News
