Comparison of NDVI-2 Vaccine EID₅₀ Titre Values After Three Weeks of Freight Under Cold Monitored Storage Condition

Abstract

The EID50 titres per dose values of three batches of NDVI-2 were determined as log10 EID50 7.7, 7.6 and 6.8 after production, against reference EID50 5.5 per dose. These values were log10 EID50 2.2, 2.1 and 1.3 above the reference EID50 for NDVI-2. These vaccines were re-evaluated at PANVAC laboratory Debre-Zeit, prior to release. The initial EID50 values were compared with EID50 values obtained by the certifying laboratory, after three weeks of cold monitored freight. The packaged vaccine cold storage temperature of +1.9 oC prior to the shipment, was recorded with the aid of a temperature logger. The temperature logger was set to record and retain packaged vaccine cold storage temperature at hourly intervals during the freight. At the end of three-week freight, the temperature logger readings were analysed, and temperature range of -2.48 oC to 7.7 oC was observed throughout the freight. However, sudden rise in packaged vaccine storage temperature from 7.7 oC to 22.28 oC was noticed on the last day of freight. The initial EID50 titre per dose values, when compared with EID50 log10 6.5, 6.8, and 6.6 per dose obtained by the certifying laboratory after the cold monitored freight and re-evaluation, showed EID50 titre loss of log10 EID50 1.2, 0.8 and 0.6, respectively. The observed EID50 loss could not invalidate these vaccine batches, considering that these had an initial EID50 titre per dose values that were well above the reference EID50 titre for NDVI-2. In Nigeria, and to our knowledge, this is the first recorded monitored cold storage temperature transit for NDVI-2.