The Premier League game between Watford and leaders Chelsea was stopped after a supporter suffered a cardiac arrest.
Referee David Coote took both sets of players off the pitch at Vicarage Road in the 12th minute with the score 0-0.
Almost 25 minutes after the game was stopped, the supporter was carried out on a stretcher and taken to hospital.
"Our thoughts are with the fan - who had a cardiac arrest but has now been stabilised - and all those affected," said Watford.
"Thank you to the medical staff, players and fans for their quick response.