Heat stability of the Rift Valley Fever Virus Clone 13 live vaccines

Rift Valley Fever (RVF) is an emerging zoonotic disease present in sub-Saharan Africa and the Arabian Peninsula. Vaccination of cattle against RVF with a RVF virus clone 13 (CL13) strain has proven to be efficacious, and avoids the side effects caused by other available live vaccines. In order to determine the temperature stability of the CL13 vaccine, lyophilized and liquid forms were tested and titrated for the presence of live virus after storage for various time periods at various temperatures. Results showed that the virus could be stored lyophilized at 4 °C for more than 12 months, with no reduction of infectivity. However, the vaccine was shown to be unstable at room temperature and at 37 °C in both lyophilized and liquid forms. This data shows that the CL13 vaccine is highly reliant on a cold chain, emphasizing the need for the vaccine to be made thermostable in order to allow for efficient vaccine storage and delivery in endemic tropical countries.