Redness and swelling at the site of inoculation were most commonly observed side reaction of JE vaccine, especially after the second injection, however, they were transitory and mild in most cases.
The first introduction of JE vaccine in Taiwan was in 1965, namely, in the field trials. 22,194 children received one dose and 111,749 children received 2 doses of JE vaccine. Almost the same number of children were inoculated tetanus toxoid as a control. To study the direct side reactions, 748 children of both groups were home visited after the first vaccination and 623 after the second, at either 24 or 48 hours after vaccination. The impression was that side reaction following JE vaccination was rather mild. Febrile reactions occurred at about the same frequency among those having the JE vaccine and those with the tetanus toxoid. Redness and swelling at the site of inoculation were most commonly observed side reaction of JE vaccine, especially after the second injection. They, however, were transitory and mild in most cases. (Table 1).