Kings of Leon have cancelled their US Tour which includes a stop at SPAC on August 20th.  Tickets will be refunded at point of purchase. Tickets purchased online or via phones will be automatically refunded.  According to a statement from the band:

We are so sorry to say Kings of Leon are canceling their entire US tour due to Caleb Followill suffering from vocal issues and exhaustion. The band is devastated, but in order to give their fans the shows they deserve, they need to take this break. Unfortunately, the US dates cannot be rescheduled due to the band's international tour schedule.

The band will resume touring in Canada at the Rogers Center in Vancouver, BC, on September 28th. That show was originally schedule for September 14th."