There's been quite a bit of research on protective equipment. Basically, headgear is ineffective as concussion is an internal brusing of the brain caused by the brain rattling around inside the skull after rapid deceleration. Head gear protects against fractured skull type injuries and skin wounds only.
The only way is to eliminate contact with the head - WR (World Rugby) are doing this by reducing the level of the tackle to the nipple line (causing mcuh wailing and nashing of teeth from those who see it as a sissy-type reaction). In tandem with this all players suspected of being concussed need to be removed from the field for assessment - this is also being done.
There's been some hiccups and resistance along the way, but rugby seems to be doing a pretty good job (compared to other sports). We just need to keep relying on medical experts and being conservative in our approach to contact with the head and concussion assessments.
http://theconversation.com/wearing-...the-risk-of-serious-injury-new-research-84887
https://bjsm.bmj.com/content/38/2/159
http://thejns.org/doi/pdf/10.3171/2016.1.FOCUS15615