Vaccine vial monitors flag heat-damaged vaccine
Imagine the challenge of getting the heat-sensitive polio vaccine from a high-tech pharmaceutical company in Belgium to a remote village in Ghana. The vaccine leaves by truck, is flown to Africa, and then is carried across dirt roads by truck or bicycle to eventually reach a refrigerator in a rural clinic that has sporadic electricity. The journey may take days or weeks, during which the vaccine is constantly at risk of being exposed to too much heat, sapping its potency. Too often in the past, heat-exposed vaccines were used because the problem wasn’t recognized or tossed out when health workers suspected that they had overheated.
To help, PATH found a technology originally used by the food industry to monitor perishable products and worked with its owners to adapt it for vaccines. The vaccine vial monitor (VVM) is a small circle, no bigger than a dime, placed or printed on a vaccine vial. The VVM changes color as it is exposed to heat, letting health workers know at a glance whether the vaccine has been damaged or can still be used for immunization.
Since introduction, these simple devices have helped ensure that vaccines are still potent when they’re used—and saved millions of doses from being discarded unnecessarily.
A small circle with a big impact
Vaccine vial monitors change color with exposure to heat. Photo: PATH.
Starting in the late 1970s, PATH worked with the World Health Organization (WHO) to find a way to track the heat exposure of individual vaccine vials. We then teamed up with the Temptime Corporation to develop VVMs suitable for vaccines used in immunization programs. Many donors provided financial support to the project, especially the US Agency for International Development. In 1996, VVMs became commercially available for oral polio vaccine, adding only a few cents to the price of each vial.
Today, WHO requires that all vaccines purchased through the United Nations Children’s Fund (UNICEF) use VVMs. And together, WHO and UNICEF have urged other groups that procure vaccines—including donor agencies, international organizations, and country leaders—to make sure VVMs are required in all of their vaccine purchase agreements and donations. PATH and WHO have also developed and tested training materials for health workers that help them learn how to handle vaccines and use VVMs effectively.
In the years since introduction, the VVM has demonstrated its value again and again. In one example, electricity went out at health facilities in Yogyakarta, Indonesia, for several days during a 2006 earthquake. Vaccine vial monitors showed that most vaccines were undamaged, despite the heat, saving 50,000 doses of vaccine that otherwise would have been thrown away.
Saving lives and resources
Today, many years after the first vaccine vial monitors transformed the transport, storage, and use of vaccines, the circles continue to serve communities worldwide. They are on every vial of the MenAfriVac® vaccine, for example, helping to protect millions of people in sub-Saharan Africa against deadly meningitis A.
Over the next decade, it’s estimated that VVMs will allow workers to recognize and replace more than 200 million doses of damaged vaccine and to confidently deliver more than a billion more doses in remote settings—saving lives and reducing illness for countless people. In addition, thanks to the presence of the VVMs on vaccines, WHO revised its policies to allow open vials of liquid vaccine to be used for more than a single day.
In 1999, UNICEF and WHO estimated that the use of VVMs on basic vaccines saved the global health community more than $5 million each year by preventing undamaged vaccines from being discarded. Figures that take into account vaccines introduced since 1999 put the projected savings at $14 million each year.
HEATmarker is a registered trademark of Temptime Corporation.