Effects of freezing on DPT and DPT-IPV vaccines, adsorbed

This paper summarizes evaluation of whether DPT and DPT-IPV from Connaught Laboratories Ltd. are visually altered by freezing in response to concern that some adsorbed DPT products can be visually unchanged, despite loss of potency from freeze damage. Data from 80 vials tested under various conditions suggest that the shake test is ineffective in field conditions. Authors recommend that a temperature-monitoring device be included with vaccines during transport, either a min-max thermometer, temperature logger, or Freeze WatchTM indicators.