Vaccine kept out of reach as encephalitis spreads

He added that no encephalitis vaccines have been prequalified by the WHO, including the mouse brain vaccine used widely in the US and Europe.

Halstead urged affected countries not to wait for the WHO's endorsement but to instead license the vaccine now and begin immunizing children in high-risk areas.

"Let's say you're making an AIDS vaccine or TB -- they're all in the `God I wish I could do it category, but I don't know how,'" he said. "Here with Japanese encephalitis, you've got a vaccine that really works. There's no need to sputter or procrastinate."