BCG immunisation for TB was routine up until 2005. The 'ring of dots' (often called the 'six needles) is called the Heaf test, and it's very similar to skin sensitively tests for allergies. The six needles introduce a tiny amount of the TB antigen into the skin and the site is examined a week later to assess the reaction - if you are already immune to TB the site will show marked inflammation, if you're not it will hardly react at all (in some cases it's hard to find the test site). My Heaf test at school reacted well - so well that the doctor was 50/50 whether to give me the jab - reading up on BCG now, it seems giving the jab to 'strong reactors' often leads to inflammation and scarring at the injection site ... explains a lot!! When I was tested again when I started nursing, and I had a VERY definite reaction - I still have a scar from those six needles!