Researchers have developed a model that can estimate regional disease burden and the impact of vaccination, even in the absence of robust surveillance data, a study in eLife reveals.
The report, originally published on May 26, highlights areas that would have the greatest benefit from initiating a vaccination program against the virus, Japanese encephalitis (JE). This will in turn guide rational assessment of the cost and benefit of vaccinations, and support policymaker decisions on allocating vaccines.
JE is a viral infection of the brain transmitted by mosquitoes. It is endemic in Asia-Pacific countries, with three billion people at risk of infection according to the World Health Organization (WHO). Only a small number of infections are symptomatic (ranging from one in 25 to one in 1,000), but people with symptomatic infections have a high risk of death (around one in three of those infected). Those who survive are often left with considerable neurological and psychological symptoms.
There are a number of vaccines available for JE, but in 2013, WHO prequalification was given to a new JE vaccine that requires only a single dose, is cheap to produce and is safer than previous vaccines. This led to a great increase in vaccination in Asia. However, given the disease’s widespread prevalence across several countries, it has not been possible to estimate the impact of these vaccinations on disease burden.
“Vaccination is the most effective method of prevention but it is difficult to decide where it should be implemented or to estimate the quantitative impact without good-quality surveillance data from before and after vaccination,” says lead author Tran Minh Quan, who was a Research Assistant at the Oxford University Clinical Research Unit, Wellcome Trust Asia Program, Vietnam, at the time of the study, and is now a graduate student at