Dear Carla,
If you look into the PQS documentation at:
http://www.who.int/immunization_standards/vaccine_quality/pqs_e04_insulated_containers/en/index.html
Vaccine carrier
PQS performance specification, E04/VC01.2 pdf, 121kb
PQS independent-type testing protocol, E04/VC01-VP.2 pdf, 109kb
You will find our requirements for vaccine carriers.
One thing we wish to see soon is to have more vaccine carriers that have a freezing prevention feature. For now the only VC prequalified that has this feature is the coldpack (E004/001)
Kind regards,
Denis