Japanese Encephalitis (JE) is a deadly viral disease that develops following the bite of an infected mosquito. It is the most common arthropod borne brain fever in the world and considered as the leading viral cause of disability in many countries of South East Asia. In areas where it is endemic, the highest attack rate occurs in children. JE is caused by a flavivirus. Viruses of this group also cause dengue fever, yellow fever and West Nile Virus fever.
The mosquitoes responsible for the spread of JE, Culex tritaeniorhyncus and Cx. gelidus feed primarily on vertebrate animals other than humans and on wading birds. When infected hosts, such as pigs, are bitten, the mosquitoes become infected.
In the wet zone of Sri Lanka where coir production is a cottage industry mosquito breeding is increased. The density of mosquitoes increases during the rainy seasons. There is a marked increase with the North East monsoonal rains (November-February).
The incubation period of JE is five to 15 days. Patients can have severe headache, sudden onset of fever, nausea and vomiting followed by change in general behaviour, stiff neck, dehydration and fits. They may go into a coma and the illness can result in death in 30%. Nearly half suffer long term neuro psychiatric sequelae. The common long term sequelae are mental impairment, severe emotional instability, personality changes and paralysis. Therefore, it is obvious that the consequences of contacting the disease is drastic
There is no specific treatment. Only supportive treatment can be given. JE requires excellent critical care and early rehabilitation.
How can we control JE?
Health education –Simple information for the general population on how to avoid exposure to mosquito bites should be given as well as motivating communities to engage in mosquito control.
Vaccination - JE control through vaccination has been well established in many countries. The experience of Sri Lanka and Thailand clearly shows the dramatic results the two countries had following the introduction of the JE vaccine. As immunization coverage increased over the years the incidence of JE has gradually declined in Sri Lanka.
Is the JE vaccine available in Sri Lanka?
Yes it has been available in SL since 1988, both in the private sector as well as by the government
How effective is the vaccine?
More than 98% effective
Are there many types
of vaccines?
There are two types-- one a live type, which is available in government clinics and the inactivated vaccine available in the private sector.
Who should get the vaccine?
Children above the age of one year or after 9 months can receive the vaccine. The inactivated vaccine is given at the age of one year and the live vaccine is given at 9 months of age
The vaccine is also indicated for travellers over one year of age visiting countries where JE is endemic.
What is the difference
between the two types?
The dosage schedule is different.
The Live vaccine - Is given at 9 months of age. Giving a booster dose is still under consideration. Live vaccine 0 .5ml is given sub cutaneously
Inactivated vaccine – Children between one-three yrs are given 0.5ml followed by a repeat dose after two weeks. In children over three and in adults the dose is one ml followed by a repeat dose after two weeks. A booster dose is required after one year.
- Inactivated vaccine is of two types
- Vaccine is prepared by inoculating mouse brain with the JE virus
- Cell culture vaccine where the virus is grown in hamster kidney cells.
- Live Vaccine
- This vaccine is prepared in hamster kidney cells
Who should avoid
the vaccine?
There are only a few reasons to avoid or postpone administration of JE vaccine
- Any history of developing a reaction to the first dose of JE
- Any history of allergy to any component of the vaccine especially gelatin, kanamycin and gentamycin
- High fever (>38°C)
- Any acute illness
- Active untreated tuberculosis
- Immunodeficiency states which include congenital immunodeficiency diseases, leukemia, lymphomas, cancers and those who are on long term steroid therapy.( They should consult their doctor)
- Pregnancy
- History of fits occurring within the last one year
- Have received gamma globulin or a blood transfusion during the last 3 months
- AIDS patients with immunesuppression.
Patients with allergic conditions should be vaccinated in an immunization clinic with facilities for emergency care.
What are the adverse reactions to the vaccine?
- Common adverse reactions are pain and redness at the injection site, which will occur within 24 hours and subside within 2-3 days.
- Transient fever
High fever is a rare adverse reaction
Extremely rare adverse reactions
- Allergic skin rashes (generally within 72 hours)
- Anaphylaxis
If JE vaccination was commenced with the killed vaccine and the full course could not be completed due to some reason, what is the solution?
The child can be given the live vaccine
Can you give the vaccine along with another vaccine on the same day?
Yes, but to a different site.
Can the vaccine be given to a child with cerebral palsy or Down Syndrome?
Yes, if child has not had a fit for the last one year.
Are asthma or other allergic conditions a contraindication?
No, but the vaccine should be given under close observation
Can adults be given the vaccine?
Yes. Since, the highest rate occurs in children, adults are not routinely vaccinated. But travellers to countries where JE is endemic should receive the vaccine.
(The writer is a Council Member, Vaccine Forum of Sri Lanka)
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