Vaccine is a prophylactic, not a cure! You can't use vaccine to treat children who have already got the infection. Also, the full course of vaccination would take a couple of months before the recipient develops effective immunity. To summarise, a mass-vaccination programme can be undertaken only after a full scientific analysis of the cost/benefit and risk/benefit ratios. Unlike diseases like smallpox, these ratios are not established for Japanese encaphalitis. Even in the case of polio, a few medical scientists are not sure that eradication of polio is possible through vaccinations, unlike in the case of smallpox.
