What is NYSIIS? NYSIIS is the acronym for the New York State Immunization Information System. NYSIIS is a free, web-based statewide immunization information system, also known as a registry, which maintains computerized immunization records of persons of all ages in a confidential and secure manner. It can immediately provide you with a child’s immunization record, even if he/she received their immunization from another provider in New York State. It saves money by ensuring that people receive only the vaccines they need and improves office efficiency by reducing the time needed to gather and review immunization records.