Effect of Extended Transit and Temperature Variations on EID50 Values of Thermostable NDVI-2 Vaccines

Temperature alterations due to poor cold keeping condition have consistently posed a challenge to vaccines dose EID50 titre value. The sensitivity of Newcastle disease vaccine to temperature variations due to poor cold storage condition in rural settings, led to the development of the NDVI-2 thermostable vaccine, which is known to exhibit a thermostability of 3 hours at 56 °C. In this study, three Newcastle disease vaccines (NDVI-2) with EID50 titre per dose values of log10 EID50 7.7, 7.6 and 6.75 respectively from vaccine production facility at the National Veterinary Research Institute (NVRI), Vom Nigeria, were sent for certification at African Union laboratory at Debre Zeit, Ethiopia under cold condition; using ice packs for cold chain maintenance. Tracking of the vaccine in the course of freight to the certifying laboratory revealed changes in the original transit route by the airline and delay by custom at the receiving country port. Thus, a 12 hours transit freight was delayed for over 7 days before arrival at the certifying laboratory. Though, the EID50 titre per dose values of these vaccines were originally well above recommended EID50 5.5 per dose value by log 2.2, log 2.1 and log 1.25 for NDVI-2 respectively. Comparing these vaccines EID50 values obtained from the certifying laboratory in relation to values initially obtained by the Quality Control Division of the producing Institute (NVRI), revealed loss of EID50 titre per dose value by log101.2, and log10 0.8 among two of the certified vaccine batches; with one of the certified vaccines retaining its original EID50 titre per dose value. This result attest that NDVI-2 thermostable vaccine produced at NVRI, Vom Nigeria are robust and of high quality. Thus, the findings of this study have further demonstrated that temperature variations, prolonged vaccine transportation under poor cold chain can affect the EID50 per dose value of a wholesome, field fit vaccine irrespective of the vaccine thermostability.