How to turn off text notifications on iPhone for specific messages?

I'm in a texting group chat with two other people, and they text way too much and I get really annoyed with them because I don't care about what they're saying half of the time and I have to concentrate on other things. Is there any way to still receive their messages, but not get a vibration without turning of my vibration completely?

You can't do this for specific messages, however you can do this for specific senders.

The easiest way would be to go to the address book entry for the people in question and set their text tone/vibration to None.

Another option would be to use the Do Not Disturb feature in the latest version of iOS. This allows you to silence calls, alerts, notifications from everyone or to permit select people.