We think of fridge holdover time (autonomy) in the context of power shortage, whether cloudy weather in the case of solar, or power cuts for A/C systems.

While this will see functioning equipment through power shortages and keep vaccine 'safe' for a given duration (a parameter which varies immensely in function of the technology chosen) if there is an actual failure in the system, we're losing out on the opportunity to notify users of the failure so that technicians can arrive on site repair the system before temperatures go out of range.

At a larger facility, one could argue that stocks can be moved from a broken fridge to a functioning one, but many community level health facilities only have that one fridge and once it goes out range, vaccine life starts dropping much faster (function of specific antigen and ambient storage temperature).

At the moment, the majority of systems just have a power LED and perhaps an LED to show that a compressor is running. If systems had a circuit that diagnosed any failure, and in turn lit up a "Fault" light, users at sites could call for help, and technicians could arrive before the device's temperature goes out of the acceptable range. In an ideal world, fridges would also be equipped with SMS capability and technicians would be notified directly of failure with a countdown based on autonomy to indicate how long they have to get to the site before vaccines are "in peril".

In the meantime, I would be curious to hear from manufacturers, for technologies currently in the field, how a user could preemptively become aware of a failure for specific products. While such diagnostics in the absence of a global "Fault" reporting system may not cover every possible failure, perhaps such knowledge, if imparted into users, could save a lot of vaccines.