Cold chain in a hot climate.

We monitored the temperatures of batches of vaccine during transport and storage from a national warehouse to five Northern Territory vaccination clinics. Electronic temperature monitors were placed with vaccines, and were programmed to record the temperature every 30 minutes for up to three months. A diary was attached to each vaccine batch to record each change in location. The temperature recordings covered 8369 hours. There were regular temperature deviations outside the recommended range. In the hot climate of the Northern Territory, freezing is the greatest threat to vaccine potency. Recommendations from the study include: routine use of cold chain indicators, increased vaccine turnover and storage of vaccines within an operational temperature range of 4 to 8 degrees C. Research is needed to investigate the efficacy of heat-stable vaccines when stored at ambient temperatures and in air-conditioned environments.