Cold chain study: danger of freezing vaccines

This report details the danger of freezing vaccine as illustrated by epidemics of whooping cough among children who have received the pertussis vaccine. One factor contributing to the delivery of compromised vaccines with poor immunogenicity, reactogenicity, and efficacy is vaccine treatment during shipping and storage. A 1992 study in Canada by the Laboratory Centre for Disease Control used Freeze WatchTM indicators to document vaccine freezing during shipment in Canadian winters. In this 1993 study, Hib-TITER vaccine was evaluated to determine the time required for this vaccine to reach the freezing point when protected by special packaging. These results show that the internal temperature of the Styrofoam box decreases rapidly and that it is likely that vaccine shipments are compromised when shipped by surface and/or air freight during the winter and that alternative packaging is required for vaccine protection while not in heated environments during winter. This paper concludes with the importance of monitoring for vaccine inactivation with single-use or reusable freeze indicators and the shake test for adsorbed vaccines.