Studies on mutation of japanese b encephalitis virus 7. an observation on persistence of immunity in children inoculated with japanese b encephalitis attenuated live vaccine sa 14 5 3 mutant
Ao, G.; Yu, Y.; Wu, P.; Li, H.; He, S.; Jia, R.
Weishengwu Xuebao 21(4): 501-505
In 1973, 49 children living in a Japanese B encephalitis (JBE) non-epidemic island were vaccinated with JBE live JBE live vaccine SA14-5-3 and a serological survey was carried out in the following 5 yr to determine the persistence of immunity. All the children vaccinated were antibody negative before vaccination. For every vaccine, 1 dose of vaccine was given in the 1st yr and a booster injection in the 2nd yr. The neutralization index (NI) tested on sera obtained 1 1/2 mo. after 1 single dose of vaccine showed a positive conversion rate of 77.6% but dropped down to 57.7% at the end of 12 mo. Following a booster injection the positive rate rose to 100% and was maintained at a level of 71-91.7% for 5 yr without further revaccination. For some children producing a high antibody level (NI 1000) after primary vaccination, a (geometric mean titer 186-660) could still be observed for 4 yr even without a booster injection.