JAPANESE
ENCEPHALITIS - SCIENCE AND TECHNOLOGY
News:
No neutralising
antibodies after Japanese encephalitis vaccination
What's
in the news?
●
A small trial in vaccinated children in
Gorakhpur district has found seroprotection against the virus decreased sharply
in fully vaccinated children.
●
A small study involving 266 children, who
had received two doses of a live, attenuated Japanese encephalitis vaccine SA-14-14-2 made in China, found very
low levels of neutralising antibodies IgG at different time points after
vaccination. It did not measure cell-mediated immune responses (T-cell immune
responses).
Key
takeaways:
●
While outbreaks of Japanese encephalitis
are reported from several places in India, the disease burden is highest in the Gorakhpur region of eastern Uttar
Pradesh.
●
Immunisation of children with the Chinese
vaccine began in 2006 in 11 endemic regions, and became a part of the Universal
Immunisation Programme in 181 endemic districts in 2011 first with a single
dose and subsequently (2013) with two doses.
●
Despite vaccination, there have been
several outbreaks in the endemic regions, particularly in Gorakhpur district.
●
The study found seroprevalence of IgG antibodies, and thus,
seroprotection against the virus “decreased in the vaccinated children”. Nearly
98% of the children who received the vaccine did not have any IgG antibodies
against the virus.
Benefits
of JenVac:
●
In contrast, a trial carried out using an inactivated vaccine (Jenvac), developed by
Bharat Biotech in collaboration with NIV Pune using a virus strain
collected in India, has found superior protection at the end of two years even
with a single dose.
●
Jenvac has been approved as a single-dose
vaccine; two doses of Jenvac are used as part of the Universal Immunisation Programme.
Go
back to basics:
Japanese
Encephalitis:
●
Japanese encephalitis (JE) is caused by mosquito-borne flavivirus.
●
It belongs to the same genus as dengue, yellow fever and West Nile viruses.
●
The first case of JE was documented in
1871 in Japan.
Vulnerability:
●
Japanese Encephalitis primarily affects children.
●
Most adults in endemic countries have
natural immunity after childhood infection, but individuals of any age may be
affected.
Transmission:
●
It is transmitted by rice field breeding
mosquitoes (primarily Culex tritaeniorhynchus group).
●
The mosquitoes transmit Japanese
Encephalitis by feeding on domestic pigs
and wild birds infected with the Japanese encephalitis virus (JEV).
●
It is not
transmitted from person-to-person.
Disease
outbreaks:
●
Major Japanese Encephalitis outbreaks
occur every 2-15 years.
●
Japanese Encephalitis transmission mainly
intensifies during the rainy season, during which vector populations increase.
Signs
and symptoms:
●
Most Japanese Encephalitis infections are
mild (fever and headache) or without apparent symptoms, but it may result in
severe clinical illness.
●
Severe infection is marked by quick onset,
headache, high fever, neck stiffness, disorientation, stupor, occasional
convulsions (especially in infants) etc.
Treatment:
●
There is no specific therapy. Intensive supportive therapy is indicated.