| cold chain monitoring of opv at transit levels in india: correlation of vvm and potency status. | we have conducted a study to analyze monitoring of the cold chain of 674 opv field samples collected at four different levels of vaccine distribution viz., immunization clinics, district stores, hospitals and primary health centers (phc) from states of uttar pradesh, madhya pradesh, and delhi. the study design included: collection and scoring of vaccine vial monitor (vvm) status of the samples and testing for total oral polio virus concentration (topv) by standard who protocol. ten samples each ... | 2003 | 14624793 |