Invisible Ink Could Reveal whether Kids Have Been Vaccinated Keeping track of vaccinations remains a major challenge in the developing world, and even in many developed countries, paperwork gets lost, and parents forget whether their child is up to date. Now a group of Massachusetts Institute of Technology researchers has developed a novel way to address this problem: embedding the record directly into the skin. Along with the vaccine, a child would be injected with a bit of dye that is invisible to the naked eye but easily seen with a special cell-phone filter, combined with an app that shines near-infrared light onto the skin. The dye would be expected to last up to five years, according to tests on pig and rat skin and human skin in a dish. The system—which has not yet been tested in children—would provide quick and easy access to vaccination history, avoid the risk of clerical errors, and add little to the cost or risk of the procedure, according to the study, published Wednesday in Science Translational Medicine.