Classical swine fever virus vaccine stability in Lao PDR

Classical swine fever (CSF) virus is a highly contagious but vaccine-preventable disease of swine. A locally produced lapinised C-strain vaccine is used to control CSF in Lao PDR; however, vaccine failure has been reported. The CSF vaccine is produced at the National Vaccine Production Centre (NVPC) as a freeze-dried rabbit spleen homogenate in a rubber stoppered glass vial and stored at –20 °C with a recommended shelf life of 1 year. This paper describes two studies to (i) determine the stability of the locally produced vaccine when stored at 4 °C and –20 °C and (ii) determine if the vaccine elicits a protective immune response when delivered to village pigs under good transport conditions. The vaccine was found to be stable for only 4 months when stored at –20 °C and for less than 3 months when stored at 4 °C. Under field conditions, vaccine stored at –20 °C for 2 months and transported at temperatures less than 1 °C elicited an immune response in 89% of vaccinated pigs by day 35 and 100% of pigs by day 70 post vaccination.