Neurovirulence, viscerotropism and immunogenicity of live attenuated yellow fever 17D vaccine virus in non-human primates.

Yellow fever vaccine associated neurovirulence and viscerotropism have been reported by various countries. In this study, the neurovirulence, viscerotropism and immunogenicity of yellow fever vaccine seed lots (master and working) and final product manufactured at Serum Institute of India (SII) were evaluated in cynomolgus monkeys. WHO reference virus 168-73 and Stamaril™ as a control vaccine was used for comparison. Neurovirulence and viscerotropism scores of the seed lots and final product were lower than Stamaril™. The SII seed virus and vaccine complies to the WHO requirement for neurovirulence, viscerotropism and immunogenicity, when tested in comparison to WHO reference seed virus 168/73. All challenged animals showed 100 % seroconversion as early as day 14 and neutralizing antibody titers were sustainable at day 30 in all animals.

A phase I clinical study to assess safety and immunogenicity of yellow fever vaccine.

Yellow fever, a mosquito-borne flavivirus infection, is an important public health problem in Africa and Latin America. A Yellow Fever vaccine (YFV) was developed and tested in a study in India. This was a Phase I, open-label, randomized, controlled study where healthy adults received SII YFV intramuscularly (SII YFV IM), SII YFV subcutaneously (SII YFV SC) or STAMARIL® (Sanofi-Pasteur) in 1:1:1 ratio. They were followed for solicited reactions for 10 days and unsolicited events for 28 days and serious adverse events for 3 months. YF-neutralizing antibodies were measured at baseline and on Days 10, 14, 28. A total of 60 adults were enrolled in the study. The proportion of participants with solicited reactions was 10%, 40%, and 25% in SII YFV SC, SII YFV IM, and STAMARIL® arms, respectively. No causally related unsolicited events or any serious adverse event was reported. After vaccination, the seroconversion was 94.44%, 100%, and 100%, in the three arms respectively. The post-vaccination geometric mean titers were similar in the study arms. The new YFV was found safe and immunogenic by IM as well as SC routes. The vaccine can be tested in further phases of clinical studies.