Rugby is much safer than most collision sport. Hitting in the sport is very controlled, not reckless like in football and hockey. There are penalties in rugby for using incorrect form while playing. Contact with the head is not that common, i have not seen many concussions in rugby.There is no such thing as a safe sport, but i have seen worse injuries in soccer and lacrosse.
If you practice a lot, have good coaches to show you the rules, and teach how to tackle properly you should be fine. Those freak accidents happen when people are reckless and don't stick to the form they were taught. It is not a very gentle sport, but it is fun :)
