What Keeps the Cold Chain Cold?

Published by Marvin Espino on

Frozen vaccine

Medicines and vaccines are temperature-sensitive products. When they are exposed to temperatures that are too high or too low, they can lose their stability or their ability to protect against diseases.

What makes them lose their stability? Read our complete guide on vaccine sensitivities to temperature and light: How Vaccine Sensitivity Affects Potency: A Guide

Once their potency is lost, it can never be regained. Hence, the way we manufacture, store, and deliver vaccines and other sensitive medicines can have a debilitating impact on their stability.

The cold chain process was designed to prevent this from happening. The cold chain requires uninterrupted refrigeration of pharma products across all levels of the supply chain, from manufacturing to the end recipient.

Medicines and other pharmaceuticals are not the only products involved in the cold chain. Some products are more freeze-sensitive, while others need to be frozen. Here is a list of the varying temperature range of the cold chain, and the products that are required to be stored within each temperature.

Deep Freeze: -25°C to -30°C (-13°F to -22°F)

The coldest temperature range in the cold chain can be achieved using active containers like refrigerators and freezers. Most products that are transported in deep freeze are seafood products, especially shrimp, and ice creams.

Frozen: -10°C to -20°C (14°F to -4°F)

The required temp range for frozen meat such as beef, pork, and poultry. Some frozen baked goods such as cakes and bread also fall into this category.

Chill: 2°C to 4°C (36°F to 39°F)

A chill range is the optimal shelf life for fruit, vegetables, and fresh meat. Because it mimics the temperature inside a normal refrigerator, products can be stored without any possibility of freezing damage.

Pharmaceutical: 2°C to 8°C (36°F to 46°F)

This storage temperature includes most vaccines, medicines, biologics, and other pharmaceuticals. This cold environment is required for either active compartments such as refrigerators, freezers, and reefers, or passive containers such as carriers and temperature-controlled packaging. Anything less or more than the specified range can spell disaster, not just for the products, but also for the logistics company, and most importantly for the end-users

Banana: 12°C to 14°C (53.6°F to 57.2°F)

Named after its most transported products, the banana temperature range is the highest temperature in the cold chain. It’s the perfect environment for bananas and other tropical fruits such as oranges and pineapples. Such fruits and produce need no freezing, but enough cooling to prevent them from ripening.  

To prevent occasions of spoilage, several devices and technologies are used by cold chain professionals and handlers. Here is a list of cold chain equipment that helps mitigate the risk of potency loss.

Active cooling devices

Examples include electric, solar or battery-powered refrigerators, and freezers. Since they require a constant connection to electricity, they are mainly used in large stores, ocean and plane shipments, warehouses, and manufacturing houses. They are typically heavy-weight, hence they cannot be used for last-mile delivery.

medial refrigerator packing


Reefers are refrigerated containers used in ocean transport. They are an example of active cooling devices as they are powered by electricity, battery, or solar panels. Used for transporting a wide array of cold chain products, reefers have larger volumes than other forms of active containers. They are also equipped with more advanced insulation and temperature sensors.

For more information on reefers, take a look at this article, (Is Ocean Shipping the Future for Pharma Cold Chain?). It explains why ocean shipment with the help of reefers might be the future of pharma cold chain transportation. A lot of pharmaceuticals are transported through air freight due to speed. Because of advancements in reefer technologies, many manufacturers are turning to ocean shipment as a viable option for intercontinental transport.

Refrigerated Unit Load Device (ULD)

Unit Load Devices are the counterpart of reefers for air transport. Refrigerated ULDs are specially made ULDs for air freight cold chain. They are pharmaceuticals’ best mode of packaging, as they have smaller volumes, for smaller needs. Plus, air-freight is also faster than ocean freight.

Cargo Loading

This article describes how air-freight certification works and what to expect in the future of pharma air-freight:  Pharmaceutical Freight Hub Certification

Temperature sensors

Since many medicines and vaccines are temperature-sensitive, placing temperature sensors in and out of the containers is good practice. Temperature reading is essential, as it prevents temperature deviations from the required cold chain range of 2°C to 8°C (36°F to 46°F).

For example, vaccine vial monitors (VVM) are sensitive papers glued on each vial of all types of vaccines. As well as detecting heat exposure, they also show when vaccines are exposed to heat, so handlers can easily dispose of them.

Vaccine Vial Monitor

This article lays out the most common temperature devices used during transport and storage: Temperature Monitoring Devices in the Cold Chain 

Other technologies to keep the cold chain cold

Some devices and technologies have proven to be paramount aids to an efficient cold chain. Among them are remote GPS trackers, advanced insulation capabilities, and centralized system software.

First, GPS helps track the location of cargo anywhere in the world, with the use of satellites. GPS has been the go-to device for intercontinental transport, where it’s less prone to emergencies and disconnection than other technologies.

AKCP Live shipment monitoring

GPS trackers placed in each package contribute to the efficient delivery of the products. Find out more in this article: How real-time monitoring reduces cold chain logistics costs

Second, advanced insulation helps further offset the loss of heat. Insulation materials in secondary packaging are getting better every year. Without insulation, passive packaging containers will be useless in maintaining a cold environment. Cooling provided by any water-packs and PCMs would be wasted without it. Today, the insulation capabilities of passive temperature-controlled packaging (TCP) can cool for several days without changing coolant packs.

The third is centralized system software. Temperature sensors can send data that will be gathered by the centralized system software. Management, from a distance, can see if there are temperature excursions, how often, and how long they last. Using the accumulated information, management can then reduce the risk of temperature deviation, cut extra budgets reserved for spoilage occurrences, and provide information to handlers and health personnel.

Here is an example of a centralized system software, showing information from multiple sensors such as temperature sensors, humidity sensors, oxygen sensors, etc.: AKCPro Server Central Management Software

How often should the temperature be monitored?

In the cold chain, the temperature should be monitored at least twice a day; first thing in the morning and last thing at night. Senior health personnel with enough experience must do the temperature logging. This is to ensure that the temperatures are accurate.

Three temperatures should be recorded: the current, minimum, and maximum. The current is the temperature at the time of logging. The minimum is the lowest temperature recorded for the whole day while the maximum is the highest temperature of the day.

vaccine storage chart

Once the temperature has been read, the thermometer should be reset. If there is a temperature excursion or levels go above or below what’s required, then health personnel should report immediately.

A technician will then assess the problem. If it’s a technical issue, then fixing the containers or the refrigerators can be the solution. Another cause of excursions can be as simple as leaving the door open. Either way, the health personnel involved must report or provide a solution.

For more information on temperature monitoring, take a look at this article: How Often Should the Temperature of a Medical Fridge be Monitored?

Cleaning and Maintaining Active and Passive Containers

One of the best ways of maintaining optimal temperatures in the containers is to regularly clean and maintain them. Fridges should be cleaned inside and out once a week. Regular servicing and maintenance can also help prevent breakdowns, which would incur increased expenses and vaccine losses.

Read further: Three Best Practices for Warehouse Monitoring

Keep Cold, Keep Effective

Several factors contribute to maintaining the cold within the cold chain.  Most of them have been detailed in this article, while a few will be covered in a different article, including the adeptness of handlers, and the ambient temperature during transport. The primary factors stated above, however, provide enough indication whether the cold chain will be a success or a failure. In striving for maintaining the cold at all levels, we seek to protect the capabilities of vaccines and medicines to save lives.  


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