Rod Stewart, 81, abruptly cancelled a scheduled concert in Chula Vista, California on Friday, just before taking the stage. The singer received urgent medical advice from his doctor deeming him unfit to perform. The cancellation is due to an upper respiratory infection resulting in a sore throat. No further details regarding the severity of the illness have been released. It is currently unknown if any upcoming performances will be affected. Representatives for Stewart have not yet announced rescheduling plans for the Chula Vista show. Fans who purchased tickets are advised to check with the venue for refund information.