Highlights•The Transcarpathian region in Ukraine has received over 350,000 Internally Displaced Persons (IDPs) since the beginning of the invasion, making the region vulnerable to outbreaks of communicable diseases.•The coverage of vital vaccination programs has been substantially harmed since the invasion began, with many children displaced without documentation and their vaccination status unknown.•The conditions in which IDPs in Transcarpathia reside risk local outbreaks of infectious diseases and their transmission into EU countries, making it vital to continue supporting Ukrainian healthcare authorities on the pivotal issue of vaccination.