How Temperatures Are Monitored In Vaccine Supply Chain: Quick Review

Specific protocols outline how temperatures should be monitored in the vaccine supply chain. In this article, we will review a number of the key points that form the foundation of this process.

What Role Temperature Plays In The Lifespan of Vaccines

Vaccines are considered sensitive assets because they are prone to damage from conditions and incidents that can occur during manufacture, transport, and storage. Once a vaccine is deemed spoiled or damaged it cannot be administered, resulting in vaccine wastage.  Although medical facilities distributing vaccines typically order more than required to account for wastage, with proper monitoring systems in place the number of wasted vaccines can be reduced.  This, in turn, reduces production costs.  Protocols related to vaccine storage and transport address temperature guidelines.  Other factors affecting vaccines quality include damaged from light exposure and trauma.

Why Vaccines Are Sensitive To Temperature

A potent vaccine triggers an immune response when administered to a patient.  But vaccines are, by nature, rather delicate.  The sensitivity of vaccines to environmental conditions puts them at risk of losing their potency if they are exposed to temperatures outside of a certain narrow range.  When potency is impaired or lost, it cannot be regained.  A damaged vaccine must be disposed of; it cannot be used.  Recommended storage and transport temperatures are provided to keep these sensitive assets in the best possible condition from the moment they leave the manufacturing plant to when they are administered to a patient.  These temperatures must remain constant to ensure the vaccines are not negatively affected.

Recommended Temperature For Vaccines and Diluents

Various temperature requirements are specific to different types of vaccines. Typically, vaccines retain potency if stored between +2C and +8C. OPV (oral polio vaccines) should be kept in freezers at -25C to -15C. Freeze-dried vaccines that are kept separate from their diluent are fine if stored in freezer rooms and vaccine freezers kept at the recommended freezer temperature range noted above. With one exception, freeze-dried vaccines bundled with their diluent must not be frozen.  The exception to this guideline is vaccines with a recommended storage temperature listed on the package insert that is outside of the temperature ranges already listed here.  COVID-19 vaccines are an example of this, with some types requiring extremely cold temperatures to maintain potency and allow for mass distribution over longer distances.

Monitoring Vaccine Temperatures

To maintain vaccine quality, temperatures must be monitored at all times. The reasons for this include:

– Verification that vaccine storage temperatures meet and remain in the recommended range

– Detection of storage temperature excursions so that rapid corrective action can be implemented

– Detection of transport temperature excursions to permit initiate corrective action

The most reliable and effective way to monitor vaccine temperatures during transport and while in storage is with data loggers. These portable recording devices use internal sensors or external probes to measure temperature.  The device can be programmed to take a temperature sample at a specified interval (twice a day, every day is the recommendation from the World Health Organization) and store that information in onboard memory.  The memory provides a recorded tracking system so that the data collected can be downloaded and analyzed. It is recommended that the temperature measuring device used contains enough memory to provide a history of readings that can be examined and that the device has fully charged batteries at the beginning of the monitoring phase.

Why A Data Logger Is Recommended

Digital data loggers are more efficient than temperature measuring by humans with an analog thermometer.  Temperature readings far more precise with a digital data logger and these devices can be placed in areas that a human cannot easily access. Plus, a data logger is made to withstand harsh environments whereas the regular exposure of a human to cold temperatures can be dangerous. Data loggers record a high volume of information that can be retrieved in several ways including direct download to a computer, remote access to a smartphone, or uploaded to the cloud for others located away from the source to access.  The information is then analyzed and can be displayed in chart or graph format for easy understanding of the readings.

Recalibration Of Temperature Monitoring Devices

Data loggers used for monitoring vaccine temperatures must be as accurate as possible.  To maintain optimum readings, temperature monitoring devices and their sensors typically require recalibration from time to time.  Several situations indicate a calibration check is required. They include:

– a regulatory body requests proof of regular calibration

– the device maker recommends regular calibration

– the device was used beyond the end date of the last calibration certificate

– a calibration certificate is missing

– the device was exposed to temperatures outside of the recommended range for use

– the batteries of the device were replaced

– measurements taken by the device seem inaccurate

The recommendation from the WHO is that all temperature monitoring devices be recalibrated at least once a year unless otherwise justified.  For devices that contain disposable plug-in sensors, recalibration must occur whenever the sensors are replaced with new ones.

Final Thoughts

COVID-19 has put new focus on the importance of vaccines.  Specific guidelines are designed to keep the vaccines intact and potent for use.  OVID-19 vaccines are some of the most sensitive medications currently in use.  This is why they require special treatment.  Cold transport and storage temperatures help maintain the integrity of these vaccines. To ensure that they remain safe for use, monitoring devices are required. Data loggers are the most logical temperature monitoring solution because of their accuracy and reliability.  Manual temperature readings are not as accurate as those taken by the digital devices recommended for use by the WHO.


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