Responding to an editorial endorsing a national vaccine registry in Canada (though the same kind of registry could be and has been proposed in the U.S. with the same logic), an anonymous reader writes "Vaccine Registration makes me think of Mutant and Superhero registration. The reasons are similar. It's based on fear and misinformation. People fear that unvaccinated people will doom us all. Sound familiar? The difference is this is real. (Oh, and they probably won't use sentinels to track down the dangerous unvaccinated folks.) Thoughts?" From the linked editorial: "A national vaccination registry would identify which Canadians have been fully vaccinated, those who have received less than a full dose of shots, and those who have not been vaccinated at all. Having a vaccine registry in place in the event of an outbreak of measles, whooping cough, and diseases like these would enable public health officials to identify the children and adults who need vaccinations. Getting them the shots they need would reduce the risk of anyone on the list getting sick, and would also reduce the threat of an outbreak in the community in which they live or travel to [and] from." In the U.S., immunization records — at least, ones which have been put in electronic form at all — are maintained in a mix of databases, including at the state level, or maintained by cities, or by insurance companies and medical providers. Here, some people (like the reader who submitted this story) also see a potential for unwarranted privacy invasion in a national vaccination registry; however, their case isn't helped by often being tied to opposition to vaccination more generally.