What is the Cold Chain and What is it Used For?

“Cold chain” is a term that gained a lot of popularity in a specific phase of the Covid-19, during the initial distribution of vaccines.

As often happens, with the passage of time and the return to normality, this word seems to have fallen into oblivion once again. But regardless of the news stories, the cold chain existed before, during, and after the pandemic and continues to play a crucial role in the logistics of many goods.

Today we are talking about the cold chain and its essential role in our society.

What is the Cold Chain?

We call the cold chain the set of operations necessary to ensure the maintenance of optimal thermal conditions for heat-sensitive products during all phases of their production, storage, and distribution.

For example, during the pandemic ground transportation needed to be equipped to keep their containers at sufficiently low temperatures to preserve vaccines.

However, this process is essential to preserve the quality and safety of a wide range of products, including foods, drugs and other biological materials.

Let's take a closer look at how it works.

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How the Cold Chain Works

Just like a real supply chain, the cold chain is based on a series of highly interconnected steps that aim to maintain products at specific temperatures, from the point of origin to the final consumer. These steps include:

• Production and Preparation: Products are produced and prepared in controlled environments, where they are immediately refrigerated or frozen.
• Storage: Products are stored in refrigerated warehouses or freezers, where temperatures are constantly monitored and maintained.
• Transport: During transport, the products are kept at a controlled temperature using refrigerated trucks, insulated containers or other specialized means of transport.
• Distribution and Sales: Distribution and sales points have refrigerated facilities to keep products at the necessary temperature until the consumer purchases them.

In which sectors is the cold chain needed and why?

The cold chain is essential in many sectors, including:

• Food Industry: The cold chain in the food industry ensures that perishable food products, such as meat, fish, dairy products, and fruit, remain fresh and safe for consumption.
• Pharmaceutical Sector: As the pandemic era has shown, many drugs require specific temperature conditions to maintain their effectiveness.
• Research Sector: Similarly, research also requires the cold chain to preserve biological samples, tissues and other sensitive materials at the appropriate temperature.

The Role of Ultra-Low Temperature Freezers in the Cold Chain

play a fundamental role in the cold chain .

We call ultra-low freezers those freezers capable of reaching and maintaining extremely low temperatures. How low?

There is no official threshold that distinguishes a freezer from an ultra-low temperature freezer. Conventionally, an ultra-low temperature freezer is one that can go below -40°C. However, most freezers stop at around -25°C.

Whilefreezers in the food sector are capable of maintaining and preserving food within the cold chain, when it comes to pharmaceuticals or biological samples, the situation is different. 

For this reason, ultra-low freezers are essential in the pharmaceutical and research industries because the temperatures required to preserve the active ingredients of these products are extremely low.

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Reference Standards

• EU GDP 2013/C 343/01 — Good Distribution Practice for medicines
• WHO Technical Report Series 961 Annex 9 — Model guidance for storage and transport of time- and temperature-sensitive products
• USP — Good Storage and Distribution Practices for Drug Products
• IATA Temperature Control Regulations (TCR) — Air Transport of Temperature-Sensitive Products
• PDA Technical Report No. 39 — Cold Chain Guidance for Medicinal Products
• EC Regulation 852/2004 — Food hygiene (cold chain)

Authoritative Sources

• European Commission — Good Distribution Practice.
• WHO — Vaccine Cold Chain.
• IATA CEIV Pharma — Airline Cold Chain Handling Certification.
• PDA — Parenteral Drug Association.

Frequently Asked Questions about the Cold Chain

What temperature ranges define the cold chain?

Four standard ranges: Frozen (-25°C to -15°C) for frozen vaccines and plasma; Refrigerated (2°C to 8°C) for most vaccines and biologicals; Cool (8°C to 15°C) for some specific products; Controlled Chamber Temperature (CRT) (15°C to 25°C) for many stable drugs. For mRNA vaccines (Pfizer/Moderna) , Ultra-Low (-80°C to -60°C) is added

How is a cold chain container classified?

The standard protocol includes unloaded and loaded thermal mapping in a climatic chamber with extreme cycles (e.g., -20°C and +40°C for 72 hours), recording with at least 9 sensors (corners + center), hold time validation, and Time Out of Refrigeration (TOR) compliance. Passive containers (e.g., Pelican BioThermal) must guarantee 72–120 hours without intervention. Active containers (refrigerated containers) require full PQ qualification.

What is the difference between static and dynamic thermal mapping?

Static mapping ( ISPE Good Practice Guide) characterizes stationary chambers/containers with temperature distribution throughout the volume (uniformity < ±2°C). Dynamic mapping records temperature profiles during actual transport (shock door-opening, airport transit, tarmac sun exposure). For full GDP qualification, a worst-case summer route (e.g., Mumbai-Frankfurt, July) is required with data loggers calibrated every 5 minutes.

What to do if a vaccine experiences a temperature change?

A Temperature Excursion Investigation: data logger collection, comparison with the vaccine's stability budget (each product has documented limitations, e.g., Pfizer mRNA tolerates 2-8°C for an additional 31 days), and batch release/reject decision. WHO publishes stability sheets for each prequalified vaccine. For non-vaccine drugs, the stability budget is based on ICH Q1A kinetics of Arrhand defined by the marketing authorization holder.