Epioentre Epidemiologie Epidemiology

Vaccination programs rely on the cold chain to store and transport vaccines safely from manufacturers to the field. However , the number of new vaccines is increasing rapidly, and many are far more expensive than those used up until now, with more complicated delivery.

For example, although innovations like single-dose vials reduce waste and protect these vaccines, they also take more space and require a more extensive cold chain. Further, the use of the cold chain constrains access to immunization in remote areas and limits the delivery potential of vaccines.

Taking advantage of the heat stability of vaccines provides opportunities for extended outreach. Some countries, Indonesia, China, and Vietnam, for example, have implemented successful cold chain strategies that extend immunization access by taking hepatitis B vaccine outside of the cold chain during the final legs of distribution. Oral polio vaccine and tetanus toxoid vaccine have also been used out of the cold chain to extend coverage and reach hard-to-reach populations.

The rationale for investigating using heat stable vaccines out of the cold chain applies not only to MSF mass vaccination campaigns, but also to improving delivery within projects. Out of cold chain use would:

• facilitate vaccination of heard-to reach populations
• facilitate the delivery of on-time birth doses
• limit the need to increase cold storage capacity and transport volumes
• limit the growth of energy needs
• reduce/eliminate the risk of freezing vaccines.

Currently, we are preparing to test several vaccines in a controlled cold chain. We are proposing to use the tetanus vaccine as a case study, as there is an efficient and heat stable vaccine available at low cost.