Not really...it would help in that situation also, though.
What I mean that the notification (vibration and/or sound) should....notify...the user there is a new message. it doesn't really help when the user gets notified half a second it has been notified. And that ten times in a row.

To avoid complications with messages received within the time a new notification may be done, and thus the possibility not have been read, I would suggest to build in a timer: when a message comes in, don't immediately notify via sound/vibration (but only visible). When within, say 5 seconds, no new message comes in, then vibrate/make sound.
If new message comes in, reset timer, but not for more than x seconds total: the situation could occur that an extreme amount of message are coming in and the timer for the notification by vibration/sound keeps resetting...