Understanding temperature monitoring in vaccine and medicine transport

Dear John,

Please note that the use of WHO‑prequalified transport cold boxes is recommended for all vaccine shipments. These cold boxes come in a range of models with different storage capacities and holdover times. They are specifically designed to maintain vaccines at +2°C to +8°C for a defined number of hours or over a specified distance, depending on the product specifications.

To ensure vaccines remain within the correct temperature range during transport, it is essential to use the appropriate number and type of coolant packs as indicated in the manufacturer’s instructions.

Each cold box is also equipped with temperature‑monitoring tools or devices to detect any temperature excursion that may compromise vaccine potency during transport.

With regard to temperature monitoring during transport, the following tools/devices are commonly used by the National Immunization Programme (NIP):

1. Vaccine Vial Monitor (VVM) - A heat sensitive label attached to each vaccine vial.
How it works:
• Changes color progressively with cumulative heat exposure.
• Provides a visual, real time indication of whether the vaccine has been exposed to too much heat.
• Cannot detect freezing; only heat exposure.
• Mandated on all UN procured vaccines since 2002.
Use in last mile: Critical in outreach sessions because it requires no power, no reading device, and works even in remote settings.

2. Electronic 30 Day Temperature Logger (30 DTR / 30 Day Logger) - A digital device placed in cold boxes, carriers, or refrigerators to log temperature every few minutes for up to 30 days.
How it works:
• Records min/max temperatures and alarm history for the previous 30 days.
• Gives health workers proof of temperature maintenance along the journey.
• Some models generate alarms when temperatures go out of range.
Use in last mile: Often used inside cold boxes during transport between one store facility to the next level.

3. Integrated Digital Thermometer (IDT) - A built in thermometer on WHO prequalified cold boxes, refrigerators, or carriers.
How it works:
• Provides continuous temperature display.
• Easy for health workers to read without opening the device.
Use in last mile: In cold boxes where available, IDT allows quick temperature checks during transport stops.

4. Freeze Indicators (Electronic or Chemical) - A device that shows whether vaccines have been exposed to sub-zero temperatures.
How it works:
• Single use chemical indicators or electronic units that trigger if the load is exposed below 0°C.
• Important because many vaccines are freeze sensitive (e.g., DTP containing vaccines).
Use in last mile: Placed inside cold boxes when frozen water packs are used

5. Remote Temperature Monitoring Devices (RTMDs) - Ble enabled or GSM enabled data loggers that transmit temperature in real time.
How they work:
• Placed inside carriers.
• Send alerts via mobile phones when excursions occur.
• Allow supervisors to remotely identify problems and guide health workers.
• Examples include ColdTrace Transport (PQS E006 102).
Use in last mile: Increasingly adopted in LMICs when network coverage exists (e.g., Tanzania).

6. Peak Temperature Threshold Indicator (PTTI) - A single use card indicator that changes color (light grey → black) when exposed above 40°C. Current use is limited to the application of controlled temperature chain (CTC) for vaccine transport of vaccines approved for CTC use.
How it works:
• Detects peak temperature events only (not cumulative exposure).
• Used for vaccines in campaigns, CTC (controlled temperature chain) applications, or where short high temperature exposure is a concern.
Use in last mile: Useful during transport in hot climates where brief temperature spikes occur (e.g., long motorbike transport, walking delivery).

7. Stem/Dial Thermometer (Low tech backup) - A simple analog thermometer used in cold boxes or carriers. No longer recommended as it is not reliable when not properly calibrated. May be used as temporary solution in post disaster settings where supply of electronic data loggers is not available.
How it works:
• Measures current temperature but does not store history.
• Must be checked frequently.
Use in last mile: Frequently used in settings with no digital devices; inexpensive and reliable as a backup.

You can find useful references in this link: https://www.who.int/teams/immunization-vaccines-and-biologicals/essential-programme-on-immunization/supply-chain/guidance

I hope this helps,

Best,
Maricel

Thank you very much! This helps a huge amount. I hope you have a good day 

Dear John, in addition to Maricel's excelent summary there are four Hot Topic pages on TechNet that you might be interested in. 

• Temperature Monitoring: Keeping a Cold Chain Cold (webinar series)
• Temperature monitoring - technical resources
• Equipment monitoring systems (EMS)
• User guides for temperature monitoring devices (PQS E006)
• Controlled temperature chain - technical resources

You can also check out the temperature monitoring page in the Knowledge Hub. 

Hope this helps.

Dear John,

All the seven tools/devices indicated by Maricel are very useful in this specific case, in adittion, we trust in the WHO‑prequalified transport cold boxes with PQS the type testing protocol made by manufactures WHO/PQS/E004/CB01-VP.3 for long range with a minimun cold life of 96 hours at 43ºC. If the time of transportation is hiher than the particular hours, we put a solar power refrigerator or freezer SDD. Like mentioned before is mandatory use this cold boxes with the number and type of coolant packs of water at 0ºC as indicated by manufacturer and avoid the vials be in direct contact with the icepacks. In this case our monitoring is take the temperature at last of the travel with a Infrared themometer. To improve the cold life, a wet white towel is put over the cold box when this cold box is transported by rivers or over the animals like horses or mules, etc. To avoid damage in the vials due to the movement during the travel, all the internal spaces must be filled with secundary packaging and plastic, mainly the diluents that are the most fragils.

One option is put a freezer AC (more shiper than SDD DC) and connect to an inversor of 500 Watts with photovoltaic panels arrangment of 500 Watts. If the place have a solar brigth and a good time of dayligth doesn´t neccesary to instal an array of batteries.

Best regards.