I don't ask either but it is a concern. I would think that the main danger would be to the child not vaccinated but of course immunizations themselves aren't guaranteed and the unimmunized child could put others at risk. But, I would feel very uncomfortble discussing children's medical histories with other parents. There's something called herd immunization that states that the more people that are immunized, the better protected the unvaccinated are. As the rates of unvaccinated children increase, the potential of the (herd immunity) effect decreases. http://www.marinij.com/marinnews/ci_12125899 I wonder if this works only in large groups or if it works on a micro scale too as in a daycare. It's a sticky issue for sure though in respecting everyone's beliefs. I also wonder why parents wouldn't want to share a copy of their child's record though if you want it. Schools and centres do. If you feel that it's important to the children's safety, or even just your peace of mind, why not. Maybe find a pamphlet about immunization schedules and leave it on a parent board as a "hint" or add medical confidentiality clause into your contract as a reassurance.