The medical team from a local hospital that oversaw the protocols for the show said an analysis of health data revealed six positive cases in the two weeks following the event among people who had attended the concert.
Organisers said none of the infected people required hospitalisation and that four of them believed the origin of their infection was from the concert.
According to Dr Josep Maria Llibre, the six infections are fewer than the average contagion spread for Barcelona at the time.
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Spanish health authorities gave special permission to allow up to 5,000 people into the venue.
Ticket holders were all told to wear masks and received the all-clear from a coronavirus antigen test.
However, there was no social distancing at the event.
The test and a mask were included in the ticket price, which cost between €23 and €28 (£20 and £24).