Global Vaccine Safety

Safety of Japanese encephalitis vaccination in India

Extract from report of GACVS meeting of 29-30 November 2006, published in the WHO Weekly Epidemiological Record on 19 January 2007

GACVS considered the report from an Indian expert panel that assessed the reported cases of serious adverse events following immunization campaigns with the live, attenuated SA 14-14-2 Japanese encephalitis vaccine in 4 Indian states during the summer of 2006. These campaigns reached >9.3 million children aged between 1 year and 15 years. A total of 65 serious adverse events were reported, 22 of which were fatal. Most serious adverse events were considered to be unrelated to the vaccine. A total of 2 clusters of encephalitis-like syndromes were identified after immunization, 1 probably representing cases of natural Japanese encephalitis and another classified as acute encephalopathy syndrome of unknown etiology; thorough investigation into possible alternative etiologies has not been conducted.

The Committee considered that the overall number of reported serious adverse events appeared low for the target population and that the type of clustering of encephalopathy and encephalitis cases made it unlikely that they were related to the vaccine. However, a better definition of cases of serious adverse events, using standard case classifications, such as the Brighton Collaboration definitions, and more active case investigation would be valuable. GACVS recommended that future immunization campaigns should be accompanied by strengthened AEFI monitoring and investigation activities.