Vaccines and antisera are biological products classified in ADR6.2 that must be stored within a certain temperature range. They are sensitive to light, warming and freezing and may be damaged under suboptimal conditions. These products are stable until the expiration date if they are kept under appropriate conditions, which are determined by the result stability tests. Although vaccines and antisera are generally stored between +2°C and +8°C, there are also vaccines requiring additional storage considerations.

The cold chain is a system consisting of people and materials, which help preserve the effectiveness of vaccines and antisera throughout the vaccination process; from production to administration. It ensures that vaccines remain efficient, and reach -in sufficient numbers-storage units, which are able to store the vaccine at a suitable temperature and meet other storage conditions before being administered to patients. If the vaccines are not efficient in achieving immunity, even if 100% vaccination uptake rates are reached, the goal of achieving herd immunity will not be achieved. Therefore, cold chain immunization is paramount to successfully implementing the vaccination program.