Approval of a new vaccine for Japanese encephalitis, initially expected this year, is likely to be delayed until 2007 or later because the government is seeking additional safety tests on possible side effects, the vaccine developers said Tuesday.

The health ministry told local-level authorities in May 2005 to suspend vaccination programs following a report that a junior high school girl who was vaccinated the previous year had developed acute disseminated encephalomyelitis, which causes inflammation of the brain and spinal cord.

In June 2005, the Research Foundation for Microbial Diseases of Osaka University applied for government approval of a new vaccine and submitted a report on its effectiveness and safety based on tests covering 300 people.

But the Health, Labor and Welfare Ministry called on the foundation for more tests covering an additional 300 people, foundation officials said.

The organization will conduct the tests so it can submit an additional report by the end of the current fiscal year.

The ministry issued a similar instruction to the Chemo-Sero Therapeutic Research Institute in Kumamoto Prefecture, which presented data covering 470 people, institute officials said.

The Japan Pediatric Society expressed concern about a longer than expected suspension of vaccinations because of the delay in supply of a new vaccine and urged the ministry to take steps to prevent an outbreak of the disease by, for example, expanding epidemic research that samples pigs.

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