Vaccine Vial Monitors

About Vaccine Vial Monitors

Vaccine Vial Monitors VVMs are small heat sensitive labels that change color when exposed to excessive heat. VVMs were developed by PATH and WHO in the 1990s and first used in 1996. A VVM consists of an inner square inside an outer reference circle; the square darkens with cumulative heat exposure. If the square is lighter than the circle, the vaccine can be used. If it matches or is darker, the vaccine is to be discarded. VVMs enable health workers to determine whether vaccines have been exposed to excessive heat during transport and storage. VVMs are particularly important in settings without reliable cold chain infrastructure. Billions of VVMs have been used on vaccine vials globally. The technology has prevented millions of doses from being administered after heat exposure and reduced vaccine wastage by allowing health workers to safely use vaccines that would otherwise be discarded.