One tool that is crucial to validating vaccine safety and is required for VFC compliance, is a data logger. Whether the vaccine is stored in an ultra-low temperature freezer or a medical refrigerator, data loggers provide real-time temperature readings for continuous monitoring during vaccine storage and handling. It’s important to note that not all data loggers are suitable for vaccine temperature monitoring.

Here are the features the CDC requires in a data logger being used specifically for vaccines:

- Detachable probe that best reflects vaccine temperatures,

- Alarm for out-of-range temperatures

- Low-battery indicator

- Current, minimum, and maximum temperature display

- Recommended uncertainty of +/-0.5° C

- Logging interval that can record temperatures at least every 30 minutes

- ISO 17025 certificate of calibration