Effects of freezing on vaccine potency

This document provides a literature review of articles about the effects of freezing on vaccine potency of hepatitis B, tetanus toxoid, diphtheria, and pertussis vaccines. Also included is a review of stability data of these vaccines at temperatures below 0°C. This document is part of a series that describes the serious risk of freezing vaccines and World Health Organization-recommended freeze-prevention strategies targeted toward all levels of storage and transport of vaccines.