Reliable storage and temperature monitoring are essential to maintain the cold chain and avoid catastrophic vaccine loss

The key to successfully completing vaccination campaigns is safely storing the vaccines until they are administered. Every time vaccines encounter heat, cold, or light, they lose efficacy. In order to maintain an ideal environment, vaccines are often stored in dedicated refrigerators and freezers—or ultralow temperature freezers (ULTs) in the case of Pfizer’s novel mRNA COVID-19 vaccine—specifically designed for this purpose. But that’s no guarantee. In January 2021, a Veterans Affairs hospital in Boston, Massachusetts, reported that they had lost 1,900 doses of Moderna’s COVID-19 vaccine after cleaning staff accidentally unplugged the cold storage unit and the freezer’s alarm failed to go off.

To ensure successful vaccine storage and avoid catastrophic vaccine loss, health care facilities should follow these four key steps.

1. Select and understand your unit
Because different vaccines have different temperature requirements, choose a pharmaceutical-grade or purpose-built cold storage unit that can effectively maintain the target temperature range. On average, refrigerators designed to store vaccines operate within the range of 2oC to 8oC, freezers between -50oC and +5oC, while ULTs reach ultracold temperatures (-86oC to -60oC) that standard freezers cannot reach.

Reliable storage and temperature monitoring are essential to maintain the cold chain and avoid catastrophic vaccine loss.
When it comes to ULTs, compressor type can affect unit longevity. A single-compressor system has one cooling cycle, while the compressors in a dual system operate in overlapping shifts, sharing the load for better longevity. However, note that toggling between the two compressors means the temperature inside the dual system freezer fluctuates +/- 5oC.

Cold storage units require good ventilation around the outside and between units and should be kept in a room with standard room temperature (20oC to 25oC).

Moreover, consider how much space is needed to store the vaccines correctly. In general, vaccines should be stored 2 to 3 inches from the inside walls and ceiling to facilitate air circulation inside the unit, which helps maintain a uniform temperature and quick temperature recovery after opening doors.

2. Monitor your unit
When doors do not seal properly, or are left open accidentally, this affects the internal temperature. A leak caused by an improperly sealed door slowly changes the temperature and may take several hours to trigger the fridge or freezer’s alarm. Door contacts can ensure doors are sealed, immediately alerting the user to an improperly closed door before the temperature is significantly altered and vaccines are lost.

But though door contacts can be an effective early warning system, an accurate and reliable temperature monitoring system is essential to protect the integrity of vaccines stored inside.

Digital data loggers (DDL) can be used to record and display the temperature inside the unit. But DDLs only log temperatures at set intervals, such as every 30 minutes, and do not record the environmental conditions in between. So, by the time a user receives an alert about a significant temperature change, the vaccines could already be compromised.

The best way to avoid vaccine loss is to use a 24-hour real-time monitoring service. Real-time continuous monitoring using a temperature monitoring device (TMD) placed at the center of the vaccine stock reflects the actual temperature of the vaccines at all times, removing any guess work. Continuous monitoring also charts temperature trends over time, preempting a significant temperature change before it happens while simultaneously reporting important information about how efficiently the unit operates as a whole. In regard to the recent incident at the Veterans Affairs hospital in Boston, a 24/7 monitoring system would have alerted staff as soon as the temperature inside the freezer began to change, potentially saving the 1,900 doses of COVID-19 vaccine.

In addition to providing peace of mind through real-time alerts of temperature deviations, a real-time monitoring service provides the most up-to-date technologies and can help manage monitoring tasks, so clinical staff can focus on what matters most—vaccinating patients.

3. Maintain your unit
Maintaining vaccine storage units is key to protecting vaccine stocks and the safety of patients. Regular maintenance includes calibration testing of TMDs against a standard device after purchase and then once every one to two years, or according to the manufacturer’s recommendations, as TMDs can drift over time.

Also, keep in mind that environmental factors can affect cold storage units. It is important to monitor the conditions in the room where units are placed, and in seasonal climates where the room temperature may fluctuate, adjust the thermostat to maintain an even room temperature.

Routine maintenance also includes checking door seals and hinges, quickly cleaning the interior to prevent bacterial and fungal growth, and keeping an eye on frost, which can interfere with air circulation and door seals.

4. Prepare for emergencies
Emergency situations often occur when we least expect them. Having an emergency protocol in place can prevent catastrophic loss of vaccines. An emergency protocol should include an alternative storage method, such as a backup storage unit in case of unit failure, or a plan to transport the vaccines to another facility, in case of a facility-wide power outage. A real-time TMD with 4G connectivity over a mobile network can also help avoid data gaps or missed alerts due to internet connectivity issues, providing accurate monitoring during a power outage.

Keep multiple copies of the emergency protocol both on- and off-site. In the event that vaccines are exposed to temperatures outside the recommended range for a significant period of time, document the incident, label the exposed vaccines, and keep them separate from the rest of the vaccine stock until you know whether they are still viable. Lastly, correct any temperature changes by adjusting the unit’s internal thermostat.

Regardless of the temperature range of your cold storage unit, continuous active monitoring is the best way to ensure the internal temperature remains within range to keep vaccines safe.