2nd Global meeting on implementing new and under-utilized vaccines, 23-25 June 2008
Japanese encephalitis vaccines
Japanese encephalitis (JE) is the most important form of viral encephalitis in Asia. It is estimated to cause at least 50 000 cases of clinical disease each year, mostly among children aged <15 years, resulting in about 10 000 deaths and 15 000 cases of long-term, neuro-psychiatric sequelae. While knowledge of the burden of disease varies by country, the prevalence of JE is increasingly recognized in countries in South-East Asia and the Western Pacific, which has led to introduction or expanded use of JE vaccines in some countries. Other countries need technical and financial assistance to initiate JE control. Given the varying epidemiologic pattern of JE in endemic countries, control strategies will need to be tailored to individual country situations.
There are currently two types of vaccine in large scale use (inactivated mouse-brain derived vaccine, and live-attenuated SA 14-14-2). Most countries favour the SA 14-14-2 vaccine which confers protection after a single dose and comes at a favourable price. However, neither of these vaccines is currently WHO-prequalified, underlining the importance of proper regulatory oversight by countries directly licensing the vaccine. Given the large scale use of the SA 14-14-2 vaccine, a better documentation of the long-term safety profile is needed. Other clarifications relate to eventual booster requirements and co-administration with measles vaccine. Several JE vaccines are in late stage clinical development, and at least two might become available for children over the coming 2-3 years.
Strong surveillance will also be critical with emphasis placed on establishing laboratory networks in both the South-East Asia and Western Pacific Regions, and on additional laboratory training to ensure enhanced case detection rates. A double layered approach to surveillance was recommended, with passive syndromic surveillance and sentinel surveillance with laboratory back-up. There was clear consensus on the need for laboratory confirmation of cases and further investigation when JE was found not to be the cause of disease.
Participants agreed on the need for a JE control strategy to sustain and accelerate progress and to attract funding. The plan should cover information on burden of disease, surveillance, diagnostics, vaccine supply, vaccination strategies and monitoring.
Recommendations
- Surveillance
- Strengthen surveillance in potentially endemic countries and enhance diagnostic capability in countries through provision of equipment, training and guidance.
- Vaccination strategy
- Develop scenario-based guidelines to facilitate country decision-making on vaccine introduction.
- Review partnership models with a view to creating an effective informal partnership to oversee further work on the development and implementation of the JE control strategy.
- Vaccine supply and safety
- Explore bilateral procurement options to ensure sufficient supply with assured regulatory oversight.
- Undertake studies to monitor vaccine effectiveness and duration of immunity with existing schedules.
- Develop and implement guidelines for monitoring of adverse events following JE vaccination.
- Clarify relevance of interference observed when live JE vaccine is co-administered with measles vaccine.