Japanese encephalitis disease and vaccine

Japanese encephalitis (JE) disease is caused by an infection by Japanese encephalitis virus. This disease is quite common in Asia-Pacific with 50,000 clinical cases reported annually.

What happens when a person catches Japanese encephalitis disease?

This viral disease leads to inflammation of the brain. Symptoms include high fever, headache, sensitivity to light, stiff neck and back, vomiting, confusion and, in severe cases, seizures, paralysis and coma. Survivors may be paralysed for life and may suffer permanent intellectual, behavioral or neurological problems.

How is Japanese encephalitis disease spread?

Culex species mosquito
Japanese encephalitis vector

Mosquitoes  of Culex species bite and spread the deadly virus. Pigs and water birds act as the amplifying hosts for the virus. The virus flourish in a transmission cycle between mosquitoes, pigs and/or water birds, a kind of enzootic cycle.

Where is Japanese encephalitis disease common?

Disease is commonly found in rural and suburbs where locals live closely with animals. Paddy fields are fertile Mosquito breeding grounds. So, in order to keep this disease at bay, we must keep the population of mosquitoes in control. In India, Assam has the highest number of cases each year in the rainy season. In 2019, JE has already killed 154, highest number since 2014.

The numbers of JE cases are vastly under-reported due to the lack of good surveillance infrastructure in affected countries. According to estimates, JE infects about 10 millions of children each year globally, killing three million and causing long term disability in four million children.

Can Japanese encephalitis disease be treated?

Japanese encephalitis cannot be treated. No effective antivirals are available. Vaccination is the only highly effective way to prevent this disease.

Which Japanese encephalitis vaccines are available in Indian market?

Effective vaccines which are cell culture-based,  are  available in market now. They have replaced the earlier available mouse-brain derived inactivated vaccines. Currently three brands of vaccines are available for use in India.

JEEV and JENVAC (inactivated) are manufactured by Indian companies, while another (live attenuated) is imported from China and is exclusively used in the Universal Immunization Programme (UIP) of the Government of India.

A new live attenuated vaccine, JE–yellow fever chimeric vaccine has recently been licensed for use in Australia and Thailand. A single dose of this chimeric JE vaccine was found to be safe, highly immunogenic and capable of providing long-lasting immunity in both preclinical and clinical trials.

 Is Japanese encephalitis vaccine a mandatory vaccine for all?

Vaccination is recommended only for individuals living in endemic areas (where JE is prevalent), like rural areas of Assam, UP and Tamilnadu. Vaccination is must even for persons traveling to endemic areas

Vaccination schedule and doses according to type of vaccine:

Type of vaccine

Minimum age

Doses

Inactivated Vero cell culture vaccine (JENVAC by Bharat Biotech)1 year
  • 2 doses of 0.5 ml each administered intramuscularly at 4-week interval
  • requirement of boosters still undetermined
Live attenuated, cell culture derived vaccine8 months
  • 2 doses, first at 9 months and second at 16-18 months along with other routine vaccines
Inactivated cell culture derived vaccine (JEEV® by BE India)1 year
  •  2 doses of 0.5 ml for children>3 years
  • 2 doses for adults aged  ≥18 years
  •  Need of boosters still undetermined

Catch up vaccination:

  • All weak children up to 18 yrs who are prone to getting sick, should be administered JE vaccine during disease outbreak/ahead of possible outbreak in endemic areas during campaign