Remote Logging of Ultra-Cold Temperature Measurements of COVID-19 Pharmaceutical Products

Remote Logging of Ultra-Cold Temperature Measurements of COVID-19 Pharmaceutical Products

By Jerry L. Eldred

Although ‘ultra-cold’ temperature measurement is not new, the Global COVID-19 Pandemic of 2020 has brought needs for this type of temperature measurement to the forefront. So for the purpose of this article, ‘ultra-cold’ refers to measurements of temperatures between -45o and -95o Celsius.

Producing or distributing new COVID-19 vaccines requires among other things, the need to continuously store them at proper temperatures. Depending on requirements of the specific vaccine, this may require refrigeration (from +2o to +8o C), frozen (from -15o to -25o C), or ‘ultra-cold’ storage (from -60o to -80o C).

The U.S. Center for Disease Control (CDC) uses the term ‘cold chain’ to describe the requirement to continuously control and accurately monitor storage temperatures to preserve the efficacy of these drugs. This begins with their point of manufacture, to storage and delivery to where they will be ultimately distributed to those who will need them.

A common required storage temperature for ‘ultra-cold’ vaccines is -70o C. Components of those vaccines begin to deteriorate beginning the moment the drug is first made. Lowering its temperature slows how quickly this happens; and   -70o Celsius is considered a safe point where its fragile chemical components remain the most stable, so that the length of time for maintaining its efficacy is maximized.

Companies that distribute or store ‘ultra-cold’ vaccines are required to maintain the CDC’s ‘cold chain’ of refrigeration. This means that they must accurately and continuously maintain and monitor -70o C.  Note that these same criteria apply to cold vaccines (-15o to -25o C) and refrigerated vaccines (+2o to +8o C).

Additionally, according to CDC guidelines, temperature measurements for these sensitive vaccines should be performed by Digital Data Loggers that record the current storage temperature of the vaccine at least every 30 minutes, and with a recommended accuracy of +/-0.5o C.

Various brands and models of wireless remote temperature data logging sensors are available commercially. Some require Ethernet via a gateway device, while others may use cellular technology. Whatever the interface method, these technologies provide the means to monitor and log ‘cold chain’ storage temperatures remotely, and to set alarms for excursions outside of acceptable ‘cold chain’ limits.

This type of data logging sensor consists typically of a wireless temperature sensing device with an extendable probe placed inside the vaccine freezer. It transmits the current temperature in the freezer at defined intervals through a gateway (or other means) back to a secured OEM-operated web page. Alarms may be sent via text or email to remotely alert the user if temperature has an excursion outside allowable ‘cold chain’ limits.

Per CDC guidelines, the remote wireless sensor should be calibrated annually or per manufacturer’s recommendations by a competent calibration laboratory. It is important to understand that the accuracy of temperature sensors drift with time. So it is not uncommon for an uncorrected measurement error at the critical ‘cold chain’ temperature of -70o C to be as much as +/-3o C.  Also, even if a sensor was generically calibrated without optimizing at its critical ‘cold chain’ temperatures, it may exhibit as much as a +/-1o to +/-3o C error.  For that reason, it is important that sensors be calibrated, adjusted and optimized at critical ‘cold chain’ temperatures. This is true for ultra-cold sensors, and other CDC compliant ‘cold chain’ types as well.

Tescom Calibration Services in Austin, Texas, recently expanded its calibration capabilities to include specialized services for ‘ultra-cold’ wireless (and other) remote logging wireless temperature sensors used where CDC ‘cold chain’ temperatures are critical, for temperatures as low as -95o C; and with calibration measurement accuracy of less than about +/-0.02o C.

Our calibration method uses a Fluke 9190A Ultra-Cold Temperature Drywell, externally monitored by a high accuracy SPRT; at customer specified temperatures, and includes optimized accuracy at customer specified critical temperatures (normally to within +/-0.5o C).  Our calibration laboratory is ISO17025 Accredited for some temperature measurements. Contact us via this website for questions, or if we can assist you with your calibration needs.

Sources:

U.S. Center for Disease Control “COVID-19 Vaccination Program Interim Playbook for Jurisdiction Operations” October 29, 2020 Version 2.0

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