Seems like they're going to track you somehow either way, they have your child's info via ssn.
With that said, I sent the opt out form in (FL)
As far as every state, most if not all have some sort of tracking system, I found this,
http://www.cdc.gov/nip/registry/privacy/legsurv.htm
but last update was 2005...
As you can see above, Wisconsin is listed as not having a registry, and/or not connected with the national registry. (the goal is to get all states connected to the national registry)
But below, you will see not only does Wisconsin have a tracking system, ANYONE who has the SSN can check the immunization records!!!!!!!
https://www.dhfswir.org/PR/portalInfoManager.do
FTR, Vermont does have a registry as well,
"The Registry was established by state law in 1997. It was designed, developed, and is operated by the Vermont Department of Health, which contributes its extensive knowledge in health surveillance, vital statistics, technology, and immunization."
http://healthvermont.gov/hc/vtimms/overview.aspx