ARE CHILDHOOD IMMUNIZATION PROGRAMS IN AUSTRALIA AT RISK - INVESTIGATION OF THE COLD CHAIN IN THE NORTHERN-TERRITORY

Since vaccines may lose their potency if transported or stored outside the recommended temperature range (2-8 degrees C), we carried out a s tudy in the Darwin area of the Northern Territory of Australia to dete rmine the links in the cold chain, including the extent of vaccine mon itoring, and whether the vaccines were being exposed to unsafe tempera tures. Sabin oral poliomyelitis vaccine (OPV) and recombinant hepatiti s-B (HB) vaccine were selected for special monitoring. A total of 127 vials of OPV and 144 vials of HB vaccine were dispatched during Octobe r, November and December 1990 to the government, independent health se rvices and general practitioner surgeries which routinely administer t hese vaccines. We distributed the two vaccines with MonitorMark(TM) ti me/ temperature and Coldside indicator tags attached to cards for reco rding the date, location and temperature exposures each time the vacci nes were moved or used. A total of 65% of the OPV and 41% of the HB va ccine monitor cards were returned for analysis. The vaccines were tran sported and stored at one to four locations prior to being administere d. Some 23% of tagged OPV was exposed for 48 hours or more to a temper ature > 10 degrees C; 47.5% of tagged HB vaccines were exposed to -3 d egrees C or less, the majority of them during storage in health facili ties or clinics. Exposures were independent of distance from the distr ibution centre, mode of transport, or type of facility. Our results sh ow that the vaccines were often exposed to temperatures outside the re commended range during transport and storage, putting them at risk of loss of potency. Freeze-sensitive vaccines were exposed to sub-zero te mperatures even in tropical climates, particularly during storage in s tandard domestic refrigerators.