RESUMEN
An effective cold chain maintenance system is the backbone of success of any immunization program. This study compares the state of cold chain maintenance during intensive pulse polio immunization campaign in union territory of Chandigarh in the year 2001 with that of 2006. The study was conducted during pulse polio rounds of December 2001 and January 2002 and another in April and May 2006 by Department of Community Medicine, Govt. Medical College, Chandigarh. Data was collected from different levels of cold chain maintenance; OPV vials were also collected and sent for potency testing at Central Research Institute, Kasauli in all the rounds. Cold chain sickness rate has decreased from 9.8% in year 2001 to 6% in year 2006. Icepacks were neatly stacked in all the deep freezers (DF) and ice-lined refrigerators (ILR). 94.71% DF's & ILR's were defrosted periodically, 95.36% temperature charts were up-to-date and signed by supervisors and no day carriers were being used in 2006 round. Whereas in 2001, the periodicity of defrosting ILR & DFs was 76.9%, vaccines were stacked neatly in only 38.46% and day carriers were being used. All the randomly selected vaccine samples were reported potent.