There no option available.
Once SEPM will update virus defination,SEP client automatic update next heart beat setting.
You can adjust the schedule that Symantec Endpoint Protection Manager uses to download content updates from LiveUpdate to the management server. For example, you can change the default server schedule frequency from hourly to daily to save bandwidth.
Configuring the LiveUpdate download schedule for Symantec Endpoint Protection Manager
See as per below Mithun comments
https://www-secure.symantec.com/connect/forums/system-running-slow#comment-6556331