Cold Chain
Temperature Monitoring

In order to maintain vaccine quality, it is essential to monitor the temperature of vaccines throughout the supply chain. Temperature monitoring devices are used to keep track of the temperature to which the vaccines and diluents are exposed. Based on the data from these devices, important decisions may be made.

Temperature monitoring devices and routines are used during every storage and during every transportation stage, until the vaccine is administered to the recipient. Depending on the supply chain level (central store, intermediary store or outreach and transportation container) different monitoring devices are used.

Monitoring Devices and Technologies

Devices for Cold Rooms and Freezer Rooms

For Cold Rooms and Freezer Rooms, monitoring devices integrate different functions like temperature and event loggers and alarm systems. They are fed by several sensors allowing the temperature monitoring in several room locations simultaneously. These systems are commonly configurable to suit user requirements by adjusting parameters such as logging interval or measurement unit.

Devices for Refrigerators and Freezers

The temperature in refrigerators and freezers is commonly monitored by the use of (analog) thermometers and (digital) data loggers. Data loggers are battery operated devices which measure and store data for a period of time. The time limit is the device memory. Some data logger models display the data instantly on an LCD screen while some other require data to be downloaded by USB or cable to a computer for later analysis.

One specific type of data logger is the 30-day electronic temperature recorder (30 DTR). This type of devices log the temperature at 10-minute intervals or less for 30 consecutive days on a rolling basis. They also record and display a 30-day history of any heat and freeze alarm violations that have occurred. Alarms are triggered if the temperature in the refrigerator drops to -0.5°C or below for 60 minutes or if it exceeds +8°C for a continuous period of 10 hours. As long as the temperature has remained within the recommended range, the device displays OK or a tick symbol. On some models, data can also be downloaded to a computer via USB interface. 30 DTRs are not designed to be used in vaccine freezers. Current models have built-in batteries with a battery alarm feature; the device must be discarded and replaced when the battery expires.

When monitoring the temperature in vaccine refrigerators (and vaccine freezers), it is recommended to apply a combined solution allowing spot temperature checks and alert displays. This can be easily achieved by the use of several devices. A convenient combination would be a 30 DTR (or other data logger) together with a stem thermometer acting as backup. When data loggers are not available, alternative alert devices such as electronic freeze indicators could be used. The use of a single standalone stem thermometer is not recommended as they only provide an instantaneous temperature reading. The minimum required monitoring equipment according to WHO recommendations is:

  • Integrated digital thermometer.
  • Stem thermometer for back-up.
  • Electronic freeze indicator.
  • VVMs where supplied.

Any device which requires frequent reading should be placed in an accessible location within the refrigerator unit and where they are unlikely to be damaged. Also consider the warmest and coolest places of the refrigerator model when placing the alert devices: If the refrigerator is used to store any freeze-sensitive vaccines, the device should preferably be placed in the coldest part of the refrigerator.

Devices for Transport Containers

For the temperature monitoring during transportation of vaccines, several monitoring devices are used:

Chemical Indicators - Also called markers or phase-change indicators). They are the most accessible and easy to use, they are based in a chemical impregnated onto a paperboard that changes its appearance under certain temperature. There are two types of chemical indicators:

  1. Threshold type.
  2. Progressive type.

Threshold Type chemical indicators provide a signal only when exposed to temperatures higher than (ascending indicator) or lower than (descending indicator) a predetermined threshold temperature. They are irreversible (thus, single-use) and are suitable for high or low temperatures.

Example of these devices are:

TempTime LIMITmarker™


Temptime FREEZEmarker®

Temperature Label
Temperature Label


Progressive Type chemical indicators register multiple events in a cumulative way. Whenever the threshold temperature is exceeded the reaction is activated and the indicator starts to change. Further temperature violations increase the change process. The indicator for this type of device usually takes the form of a progressive colour change along a paper strip.

    Cold Chain Monitor (CCM) Card

    Paper-based temperature monitoring device which change colour irreversibly and at a constant rate. Indicator strips are attached to a card on which instructions for use are printed.

    CCMs provide a warning when excessive heat exposure occurs during transport. They are used primarily to monitor the international shipment of freeze-dried vaccine consignments where dry ice is used. CCMs may also be appropriate for national vaccine shipments where the delivery takes several days.

    Cold Chain Card

    Vaccine Vial Monitor (VVM):

    Heat-sensitive label that gradually and irreversibly changes colour as the vaccine is exposed to heat. It warns the health worker when a vial should be discarded because the vaccine is likely to have been degraded by exposure to heat. For instructions on how to interpret VVM, refer to WHO How to Monitor Temperatures in the Vaccine Supply Chain.

    Vaccine Monitors

    Electronic Freeze Indicators - used to check if vaccines are exposed to freezing temperatures during storage or transport. The alarm indicator is triggered and displayed (changing from a “√” to an “X”) if exposed to temperatures lower than -0.5 °C for a continuous period of 60 minutes. To avoid malicious manipulation, once the alert is triggered, the alert is irreversible. If this happens the device is no longer usable and should be discarded. Otherwise, the device can be used until the built-in battery expires. The intermittent “dot” icon confirms active monitoring.

    Freeze Alert
    Electronic Freeze Indicator
    Electronic Freeze Indicator

    Electronic Shipping Indicators - more sophisticated devices that show if a product has been exposed to temperatures beyond the assigned alarm settings. They record the temperature at regular intervals during a certain period (normally not exceeding 20 days due to memory overflow). They have a digital display that reflects if the vaccine being shipped crossed the alarm thresholds.

    Shipping indicators are mounted on a coloured card (yellow or blue) with a data entry section on one side, which the manufacturer fills in at the point of dispatch, and an instruction and interpretation section on the reverse side for the recipient. Yellow indicators are for freeze-sensitive vaccines, and blue indicators are for heat-sensitive vaccines.

    These devices are not re-usable once alarm conditions are triggered or the programmed time elapses. In addition, the heat and/or freeze alarm thresholds are product-specific, which means that the device is not reusable with different vaccines. Some brands are able to download the temperature data to a computer. This enables recipients to determine whether shipments have been exposed to excessively high or low temperatures; it also helps the procurement agency to determine when, where and to what extent temperature limits have been exceeded.

    Electronic Shipping Indicator 3
    Electronic Shipping Indicator 2
    Electronic Shipping Indicator 1

    Temperature Monitoring Routines

    Temperature-monitoring and record-keeping are required to make sure that each vial of vaccine is maintained under appropriate conditions. The data gathered from temperature monitoring devices must be recorded and analysed on a regular basis to demonstrate that vaccines are being stored and transported at the correct temperatures.

    A standard recommended practice for secondary/intermediary storage facilities and health facilities is to check and record the temperatures in the refrigerators at least twice a day, in separated intervals: first thing in the morning and at the end of the working day is considered a good practice. Alert displays should also be revised. This should be done every day of the year, including days off.

    At each spot check the temperature should be recorded. This should be done on a standard temperature chart. The chart should be attached to the door of the specific fridge/refrigerator being monitored. Completed charts should be filed together for future reference.

    Temperature Monitoring Chart:

    Temperature Monitoring Card


      Download - Temperature Monitoring Chart

      For monitoring the temperature of cold rooms, temperature checks should be also done twice daily, but at each inspection, it should be read the temperature record for the entire period since the last reading.

      If during a temperature check in a cold room or refrigerator:

      • Temperature is at or below 0°C or a freeze alert is activated: immediate action should be taken to correct the low temperature and to ensure that the problem does not arise again. The agreed contingency plan should be triggered and a report completed.
      • Temperature is between +8°C and +10°C: check that the refrigeration unit is working, monitor the situation closely in the following hours and take appropriate action if the temperature is not within the normal range at the time of the next inspection. If there was a temporary power failure, no further action on fridge or cold room would be necessary.
      • Temperature is above +10°C: activate immediately the agreed contingency plan, and make a report.

      If during a temperature check in a freezer room or chest freezer:

      • Temperature is below -25°C: Adjust thermostat. Check that the temperature is within the normal range at the time of the next inspection.
      • Temperature is above -15°C: Check that the refrigeration unit is working, monitor the situation closely and take appropriate action if conditions are not normal at the time of the next inspection. If there has been a temporary power failure, no further action is necessary. A temporary rise to +10°C is permissible following a temporary power cut.
      • Temperature is above +10°C: Take immediate action to implement the agreed contingency plan, and make a report.

      Managing Cold Chain Ruptures

      Every storage facility should develop a contingency plan for the event of a cold chain rupture. The plan should be accessible, allowing the staff to know what to do when the event happens. Contact numbers for key persons to be urgently contacted in such event and emergency cold chain storage capacity for back-up is information that must be included.

      Passive cold chain can be used as temporary backup storage. In that case:

      • Provide enough cold boxes to store products temporarily.
      • Always have the required number of frozen icepacks available for the cold boxes.
      • Increase the frequency to monitor the temperature.

      In case of cold chain rupture, the following actions should be taken:

      • Identify the affected products, mark them and place them in quarantine to avoid its use temporarily. A quarantine area should be clearly marked for this purpose in one functioning cold chain equipment.
      • Write a cold chain breakdown report and send it to the relevant persons. It must be submitted as soon as possible. The report should include information about the products (name, manufacturer, batch number, expire date, quantity) and the details of the Cold chain rupture (temperature range, exposure time, source of the alert).
      • Wait for pharmacist recommendations. Even if some cold chain break occurred, the vaccine could be used under certain instructions. In case that the vaccine must be discarded, proceed according to the national regulation.
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