Important considerations in choosing a refrigerator/freezer temperature monitoring device

The temperature monitoring device (TMD) being used to ensure the viability of the refrigerated and frozen vaccines and medications stored in the pharmacy is an often-overlooked area. Unfortunately, inaccuracy can lead to the administration or dispensing of medications that have been stored outside of recommended temperatures.

Why is this a problem? Vaccines and any medication stored outside manufacturer-recommended temperatures can quickly lose potency and thus efficacy. Administering a vaccine that has been stored improperly can be worse than not administering a vaccine at all due to the fact the patient will actually believe they are protected.

In addition, administration and storage errors can breed public distrust in vaccines and in healthcare as a whole as well as expose the pharmacist and the pharmacy to potential liability. In an upcoming article, I'll go over the mechanisms behind vaccine degradation.

That being said, here are some important considerations when choosing a thermometer for your pharmacy:

1. TMD type: According to the CDC Vaccine and Storage Handling Toolkit, a Digital Data Logger (DDL) is the preferred type of TMD. The primary advantage of a DDL is that it can record temperatures automatically in intervals; the CDC recommends that a DDL record at least every 30 minutes. These recordings are typically downloadable onto an Excel spreadsheet, and there are now many types of thermometers that can send data and/or alerts to a smartphone as well.

In the past, TMDs that would only record a min-max were commonly used, but this could lead to a lot of waste in the case of an excursion. I remember an incident where the pharmacy had an excursion and was recording temperatures twice daily, including a min-max (the standard of practice at the time). Unfortunately, that means the readings were about 12 hours apart and we had a medication that the manufacturer had stability data for going out 8 hours, but not 12, so we had to throw it away. It was a $3000 medication! Moral of the story - invest in a quality temperature monitoring device.

Types that are not allowed include (more comprehensive list in CDC document):

  • Food thermometers

  • Thermometers that measure air temperature only

  • Chart recorders

  • Mercury or alcohol-filled thermometers

2. Certificate of Traceability: Just like a pedigree in fine art tracing ownership of the work back to the artist (or even a pedigree in DCSCA compliance tracing a drug back to the manufacturer), a TMD calibration must be able to be traced all the way back to global uniform standards. In the US, the National Institute of Standards and Technology ensures uniform measurement standards; globally, the BIPM (Bureau International des Poids et Mesures), consisting of member-states, ensures accuracy of measurement.

3. Certificate of Calibration: TMDs, like any other instrument, must be calibrated to ensure accuracy. Just like in medicine and many other fields if it isn't documented it wasn't done. Very important to note - these certificates expire; when they do, the thermometer must be replaced. While the CDC does note that you can send it off for calibration testing again and replace it if it fails (note: calibration does not necessarily mean adjusting the TMD - it only means measuring its accuracy), temperature monitoring devices are cheap enough this is not really practical or worth it. In other words, temperature monitoring devices do expire and must be replaced!

In summary, a Certificate of Traceability ensures the instrument used to calibrate your TMD is accurate to global standards, while the Certificate of Calibration ensures the accuracy of your TMD.

4. Other features:

  • Buffered probe (often filled with glycol, and intended to mimic conditions inside the vial of the vaccine)

  • Alarm for out-of-range temperatures (again, many offer alarms connected to a smartphone)

  • Current as well as min-max display

  • Recommended uncertainty of +/- 0.5 degrees Celsius (+/-1 Fahrenheit)

Although not a CDC recommendation, I personally recommend having two TMDs per refrigerator (CDC recommends just one for the facility as a backup). It is a minimal additional cost (especially compared to the cost of all the medications and vaccines being stored in the refrigerator) and I have seen them have occasional problems - batteries die (best practice is to plug it in and not use batteries, by the way), a button gets hit and it stops reading, it turns off, etc. Just see the below pictures I took in one of my pharmacies where that actually happened (both pictures were taken at the same time).

Upon further investigation I confirmed it did not reach 32 degrees; the TMD was listing a previous low that was prior to it being placed in this refrigerator. Having my backup gave me peace of mind while I investigated the one that went awry.

Of note, here I am referring to two thermometers that are recording the temperature at the same time, not one that it is in the refrigerator and one sitting in a box somewhere.

TMD's like this one, from Thomas Scientific, are not only fully compliant with CDC recommendations but temperature data can be pulled off the device and onto a computer. This one holds 525,600 temperature data points.

Once you get the TMD, be sure to get everything set up properly and best protect your business from temperature excursions.

Ensuring that you are up to date with the latest guidelines on vaccine storage and handling can be a daunting task. One of the best places to start, in addition to the CDC Vaccine Storage and Handling Toolkit, is, which has numerous free resources related to vaccine storage, administration, education, and more.

Keywords: Cold chain, thermometer, temperature monitoring device, vaccine