Cold chain

A cold chain is a temperature-controlled supply chain. An unbroken cold chain is an uninterrupted series of refrigerated production, storage and distribution activities, along with associated equipment and logistics, which maintain quality via a desired low-temperature range. It is used to preserve and to extend and ensure the shelf life of products, such as fresh agricultural produce, seafood, frozen food, photographic film, chemicals, and pharmaceutical products. Such products, during transport and when in transient storage, are sometimes called cool cargo. Unlike other goods or merchandise, cold chain goods are perishable and always en route towards end use or destination, even when held temporarily in cold stores and hence commonly referred to as "cargo" during its entire logistics cycle. Adequate cold storage, in particular, can be crucial to prevent quantitative and qualitative food losses.
History.
Mobile refrigeration with ice from the ice trade began with reefer ships and refrigerator cars (iceboxes on wheels) in the mid-19th century. Mobile mechanical refrigeration was invented by Frederick McKinley Jones, who co-founded Thermo King with entrepreneur Joseph A. "Joe" Numero. In 1938 Numero sold his Cinema Supplies Inc. movie sound equipment business to RCA to form the new entity, U.S. Thermo Control Company (later the Thermo King Corporation), in partnership with Jones, his engineer. Jones designed a portable air-cooling unit for trucks carrying perishable food, for which they obtained a patent on 12 July 1940, subsequent to a challenge to invent a refrigerated truck over a 1937 golf game by associates of Numero's, Werner Transportation Co. president Harry Werner, and United States Air Conditioning Co. president Al Fineberg,
This technology has been frequently in use since the 1950s, when it was most often used for preserving animal-based cells or tissue. As medical breakthroughs, such as in cancer treatment, have taken place, the demand for cold chain systems has grown. The COVID-19 pandemic and its associated vaccinations, have caused vastly increased need.
Uses.
Cold chains are common in the food and pharmaceutical industries and also in some chemical shipments. One common temperature range for a cold chain in pharmaceutical industries is , but the specific temperature (and time at temperature) tolerances depend on the actual product being shipped. 
Produce.
Unique to fresh produce cargoes, the cold chain requires to additionally maintain product specific environment parameters which include air quality levels (carbon dioxide, oxygen, humidity and others).
Vaccines.
The cold chain is used in the supply of vaccines to distant clinics in hot climates served by poorly developed transport networks. Disruption of a cold chain due to war may produce consequences similar to the smallpox outbreaks in the Philippines during the Spanish–American War, during which the distributed vaccines were inert due to lack of temperature control in transport.
For vaccinations in particular, there are different types of cold chains. There is an ultralow, or deep freeze, cold chain for vaccines that require -70 degrees C. The Ebola and Pfizer–BioNTech COVID-19 vaccines require this level, as do some animal vaccinations, such as those for chickens. Next the frozen chain requires -20 degrees C. Varicella and zoster vaccinations require this level. Then the refrigerated chain, which requires temperatures between two and eight degrees C. Most flu vaccinations only require refrigeration.
In 2020 during the COVID-19 pandemic, vaccines being developed may need ultracold storage and transportation temperatures as cold as , requiring what has been referred to as a "colder chain" infrastructure. This creates some issues of distribution for the Pfizer vaccine. It is estimated that only 25 to 30 countries in the world have the infastructure for the required ultracold cold chain.
Validation.
The cold chain distribution process is an extension of the good manufacturing practice (GMP) environment that all drugs and biological products are required to follow, and are enforced by the various health regulatory bodies. As such, the distribution process must be validated to ensure that there is no negative impact to the safety, efficacy or quality of the drug substance. The GMP environment requires that all processes that might impact the safety, efficacy or quality of the drug substance must be validated, including storage and distribution of the drug substance.
A cold chain can be managed by a quality management system. Temperature data loggers and RFID tags help monitor the temperature history of the truck, warehouse, etc. and the temperature history of the product being shipped. They also can help determine the remaining shelf life. Also, temperature sensors may need to be National Institute of Standards and Technology (NIST) traceable depending on the body monitoring the cold chain. 