If you want information on the CP vaccine, varicilla go to the department of health website and go to childhood immunisations..

Immunise - Immunise Australia Program

there you can view the immunisation handbook which has all the information for and against vaccination and information on risk factors and reactions etc.

as far as im aware the 18mo one is not compulsory, though i did get DD1 done..

the vaccine is the same as any it only has a life of 7-10 years within the immune system as the immune system replenishes and becomes new after a period of time, but it has a memory and will remember certain illnesses and immunisation/vaccinations.
the reason you have a booster is to remind the immune system what its trying to defend.

i just find it interesting how people decide to not immunise. and feel well its not prevelent in my area so i dont need to. but the reason its not prevelant is because people are immunising against an illness to help reduce its occurance and its working.
the more people who do not immunise the more chance there is of an illness coming back

this was evident when they stopped immunising against TB in a certain country within 5 years the incidence of infection rose by 70% so they soon re introduced the immunisation.

i am all for witholding and delaying immunisations for medical reasons and for people who are well informed, but the simple reason, oh you never see anyone with that now is silly as there is a reason why its not common..

sorry ill get off my high horse now..