There were no significant COVID-19 outbreaks following a mid-sized rock concert held in Barcelona in March, the organisers have said.
Festivals per la Cultura Segura are now arguing that similar events can be held without social distancing and other COVID-19 precautions.
The concert was held at the Palau Sant Jordi arena, with 5,000 music fans allowed to watch indie rock band Love of Lesbian.
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).
A group of concert organisers behind the initiative described it as a pilot programme to help restart cultural events with the sector suffering after a year of pandemic restrictions.
"There is light at the end of the tunnel," organiser Jordi Herreruela said about the results.