Back in the old days, being below a certain % prevented an assassin from assassinating you.

The other day I was at 60% health, and an assassin was able to attempt an assassination.

Now, does being below a certain health % reduce the chance of an assassination and no longer prevent an attempt?

Or below a certain % you can no longer be assassinated, but an attempt can still be made anyway.

Thanks for clarification - helpfiles were silent on this.