If anyone, infant or adult, have had a full course of hep b vaccinations they will never require a booster, the only exception to this is immunosupressed individuals ie people having chemo or those that are HIV positive.
With regard to the need for infants to have it done, well hep B can actually be passed on through non sexual household contact, ie by touching open cuts or sores of an infected person. You do have a right to choose in Australia, vaccination is not compulsory here, no school, preschool, childcare centre or playgroup is legally allowed to refuse a child because of their vaccination status.
Everyone needs to be aware however that both Tax Benefit Supplement and the Childcare Allowance are both affected by vaccination compliance. If you choose not to fully vaccinate your child you will need to get a GP or someone who has an immunisation provider number – to sign a Conscientious or Medical Objection form.
As for chicken pox, it can be and is a killer, just because it is something we all had as kids does not make it harmless, mumps, measles, whooping cough etc we're all common 30 or 40 years ago, it doesn't make them harmless, my sister has been deaf since childhood as a direct result of mumps. The most common serious complications that arise from chicken pox are pneumonia and encephalitis.
I am not a "drum beater" for child immunisations but I do think that they are there for a reason, they are not being provided for free to every child just for fun, there has been years of research regarding what is necessary. There is an infinite amount of stuff to be found on the internet with regard to the right/wrong thing to do, just be aware of who wrote what you are reading and keep in mind there are two sides to every coin.