Neither are you Pixie.
I'll tell you how.
I know my children do not have vaccination acquired immunity. I therefore take more care. I know what the first symptoms of these diseases are. I don't assume they can't carry them and can't pass them on. I keep my children off school with a raised temperature of any degree. I know how to look for Koplik's spots, for example, which can appear before measles rash or other symptoms. I have a very high awareness of local disease incidence and report. Guess what: this is not just to protect my child. I am not stupid.
Now none of that guarantees they can't catch something. Rubella, for example, can be extremely mild and the symptoms difficult to spot.
However as parents of vaccinated children seem to be confident they cannot pass on disease, they do not take these precautions.
Imagine a secondary school of, say, 1000 children. What's the MMR uptake, I don't know, it varies doesn't it. Say it's 85 to 90 pc. That's 100 to 150 children.
Now say 95pc of vaccinated children do not take. That's fifty children. How many in whom it's worn off? Who knows. A lot, judging by the fact that so many boosters are needed and the mumps epidemics among adolescents. Say it bumps it up to 100 children.
So you've got 250 children non-immune in the school, all able to catch and pass on a disease. Who's to say unvaccinated can't catch it from vaccinated? They can, of course.
How many of the vaccinated parents imagine their children are susceptible if there's no publicised outbreak? I would imagine about none at all.
So that's why my children are less of a risk: because I know about their risk status.
I would also second bubbleymum when she points out that vaccination is the reason these diseases have moved into vulnerable groups, such as babies and adolescents.
So the risk to those groups is enhanced by what you are most vigorously defending.