Digital data loggers (DDLs), also called “continuous temperature monitoring devices” or just “data loggers,” continuously read and record temperatures to provide an accurate report of vaccine temperatures over time. DDLs also alert clinic staff when temperatures are out of the recommended range via visual, audible and/or electronic notifications. DDLs read and record temperatures at set time intervals and store data in an internal memory. Clinic staff can download and save the data as an electronic file on a computer and analyze vaccine storage unit temperature trends over time.
All VFC providers must use a VFC-compliant DDL in every refrigerator and freezer storing VFC-supplied vaccines. Practices also must have at least one battery operated backup DDL to use when a primary device is being calibrated, during emergency vaccine transport, or if a primary device fails. Depending on the size of the practice, additional devices may be needed. Every device must have a valid and current certificate of calibration on file.
Because monitoring devices experience a “drift” over time that affects their accuracy, DDLs must be certified for accuracy every two years, or three years when manufacturers recommend a period longer than two years. Calibrate primary and back-up devices on different schedules to ensure all refrigerators and freezers are always equipped with data loggers with a valid and current certificate of calibrations. VFC also encourages calendaring calibration testing so that it is done at least 2-3 months prior to a DDL’s expiration date. DDL expiration dates should be documented on the clinic’s Vaccine Management Plan.
In preparation for the annual VFC Program Recertification process, clinics are strongly encouraged to verify all their DDLs are calibrated and that the certificates of calibration are current.
Importance and Use of Data Loggers
Data loggers
- monitor vaccine temperatures continuously—even when the practice is closed,
- may have alert capabilities to notify clinic staff of temperature excursions during non-business hours,
- determine how long vaccines have been exposed to out-of-range temperatures,
- prevent unnecessary vaccine losses when excursion time frames cannot be precisely determined, and
- show how a storage unit’s temperature increases and decreases over time.
Data Logger Specifications
Participating providers agree to comply with device specifications provided by the California VFC Program. Data loggers must meet these requirements:
Feature
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Description
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Accuracy
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+/-1.0°F (+/-0.5°C)
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Logging interval
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Programmable (at least every 30 minutes)
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Memory storage
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4000 readings or more
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Buffered temperature probe
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- Only use the buffered probe bundled with the device
- Detachable from unit, or permanently embedded in a buffer as long as the temperature monitoring system can be calibrated
- Immersed in a vial filled with thermal buffer material, including liquid up to 60 mL (e.g., glycol, ethanol, or glycerin), loose media (e.g., sand or glass beads), or a solid block of material (e.g., Teflon® or aluminum)
|
Digital display
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- Active external display
- Must include current, MIN, and MAX temperatures
- Must be in close proximity to the vaccine storage units and temperature logs
- Low-battery indicator
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Alarm capabilities
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- Programmable
- Visual or audible alarm to signal out-of-range temperatures
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Reports
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- Must generate a summary report of recorded temperatures that include minimum and maximum temperatures
- Total time out of range (if any), and alarm settings
- Generates PDF or secure PDF reports
|
Also, data loggers must meet current calibration and recalibration requirements.
Unacceptable Temperature Monitoring Devices
Any device that does not meet California VFC Program requirements is prohibited, including but not limited to
- thermometers (e.g., round dial thermometers, fluid-filled and/or min-max bar thermometers, household-use and kitchen thermometers, infrared temperature guns, alcohol or mercury thermometers, and bi-metal stem thermometers);
- chart recorders, which are units that plot temperatures on printed graphs;
- data loggers that do not have probes immersed in a vial filled with liquid, loose media, or a solid block of material; and
- new devices that only generate CSV data files or Excel spreadsheets.
Purchasing Considerations
There is a wide range of data loggers on the market that come with features that may better suit your needs than just the basic models. Data loggers might be simple, stand-alone devices or more sophisticated with enhanced functions such as cloud-based technology and remote access to temperature readings.
The California VFC Program does not endorse or promote specific temperature monitoring devices. Use the VFC Data Logger Feature Comparison Guide as you research devices to meet practice needs.
2020 update: New devices must be able to generate a summary report of recorded temperature data since the device was last reset; summary reports must include minimum and maximum temperatures, total time out of range (if any), and alarm settings. Devices that only generate CSV data files or Excel spreadsheets are not acceptable.
See also Questions to Ask Vendors about Digital Data Loggers.
When You're Ready to Purchase
Many companies sell data loggers, but specialized medical equipment suppliers and manufacturers’ distributors are generally more knowledgeable and offer the best information about them.
Consider using the VFC Digital Data Logger Pre-Purchase Worksheet to select the device for purchase.
Here are some product vendors and/or distributors. This list is not exhaustive and includes only common search results: Control Solutions, Inc, Dickson, Onset, and Traceable products.
Purchase and Maintenance Resources:
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