What is a cold chain?

A high-quality cold chain allows health workers to deliver life-saving vaccines to every last child.

Permanent link toA community relay crosses a water stream with his bike to vaccinate children the most distant children in the health zone of Manono, Tanganyika Province, Democratic Republic of the Congo
UNICEF/UN0328787/Wingi

Delivering vaccines to all corners of the world is a complex undertaking. It takes a chain of precisely coordinated events in temperature-controlled environments to store, manage and transport these life-saving products. This is called a cold chain.

Vaccines must be continuously stored in a limited temperature range – from the time they are manufactured until the moment of vaccination. This is because temperatures that are too high or too low can cause the vaccine to lose its potency (its ability to protect against disease). Once a vaccine loses its potency, it cannot be regained or restored.

How do vaccines move along the cold chain?

When UNICEF sends vaccines, they always travel directly by plane from the manufacturer as refrigerated cargo to the country where they will be used. Once they land, they are stored in cold rooms before being distributed to regional and sub-regional cold storage facilities by refrigerated vehicle. From storage facilities down to the village level, health workers carry vaccines in cold boxes and vaccine carriers, traveling by car, motorcycle, bicycle, donkey, camel or on foot to immunize every last child, even in the most remote of villages.

Storage and transport equipment such as cold rooms, refrigerators, freezers, cold boxes and vaccine carriers must comply with performance standards defined by the World Health Organization (WHO). Stock management procedures must also follow WHO guidelines specific to each type of vaccine.

UNICEF procured close to USD 100 million worth of cold chain equipment and services in 2018. We work closely with partners and governments to ensure the cold chain continues to work effectively and efficiently in every country where we deliver vaccines to children. Learn more about this work and the Cold Chain Equipment Optimization Platform (CCEOP) through the links that follow.