Recommendations for UseJE vaccine should not be used as an “outbreak response vaccine”. IAPCOI recommends that the government should implement universal immunization with this vaccine in all children in JE endemic states. The SA-14-14-2 vaccine appears best suited for this purpose. A recent study from Phillipines shows acceptable efficacy and safety of this vaccine when co administered with the measles vaccine at 9 months. Along with all infants, all susceptible children upto the age of 15 years should be administered catch up vaccination. JE vaccine is also recommended for travelers to JE endemic areas provided they are expected to stay for a minimum of 4 weeks in rural areas in the JE season. |
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Japanese encephalitis (JE) is one of the most important causes of viral encephalitis in Asia. Japan, South Korea, North Korea, Taiwan, Vietnam, Thailand, and the Peoples Republic of China (PRC) practice routine childhood immunization against JE. In India, JE is believed to be responsible for approximately 2000-3000 clinical cases and 500-600 deaths every year. JE has been reported from all states and union territories in India except Arunachal, Dadra, Daman, Diu, Gujarat, Himachal, Jammu, Kashmir, Lakshadweep, Meghalaya, Nagar Haveli, Orissa, Punjab, Rajasthan, and Sikkim. Highly endemic states include West Bengal, Bihar, Karnataka, Tamil Nadu, Andhra Pradesh, Assam, Uttar Pradesh, Manipur, and Goa.
The risk is highest in children aged 1-15 years, in rural areas and in the monsoon/post monsoon season. Periods of greatest risk are May to October in Goa, October to January in Tamil Nadu, August to December in Karnataka (second peak, April to June in Mandya District), September to December in Andhra Pradesh, and July to December in Northern States. Urban cases have been reported from Lucknow. JE vaccination remains the single most important control measure in JE endemic states of India.
This vaccine is prepared from either the Nakayama/Beijing strain of JE virus grown in mice brain, purified, inactivated by formalin and preserved with thiomersol. No myelin basic protein is detectable in the finished product. Efficacy trials in Taiwan and Thailand demonstrated 80-91% efficacy with two doses of the vaccine. The vaccine is given subcutaneously – 0.5 ml in children 1-3 years, and 1 ml in older children. Primary immunization consists of three doses given on 0, 7 and 30 days. In special circumstances when time is short a 0, 7 and 14 day schedule may be used. Two doses 7 days apart provide only short term immunity in 80% of vaccinees for 6 months and may be used in travelers for logistic reasons. The last dose should be given at least 10 days prior to travel to the endemic area. For long term protection regular boosters every 2-3 years are recommended.
Common adverse reactions include fever, malaise, local tenderness and redness in 20% of recipients. Acute neurologic events have been reported in 1-2.3 per million vaccinees. Allergic reactions mainly Type I hypersensitivity reactions including anaphylactic shock have been reported at a frequency of 1-100 per 10,000 traveler vaccinees varying with different batches of the vaccine. The risk of reactions is higher in those with history of hypersensitivity.
All vaccinees should be cautiously monitored for possible allergic reactions and asked to remain in the vicinity of medical facility for 10 days after vaccination. Owing to drawbacks (high cost, complicated dosing schedule, requirement of numerous doses and boosters, concerns about sideeffects and reliance on neurological tissue for production) and availability of better vaccines, the production and availability of this vaccine has markedly declined in the current scenario.
This vaccine made from Primary Hamster Kidney cell line was used in China in millions of doses but has now been given up with the availability of the SA14-14-2 live vaccine. Clinical trials with vero cell derived inactivated vaccines are currently in advanced stages of clinical trials in Japan, Taiwan, South Korea and China and show promising results.
This vaccine is based on a stable neuro-attenuated strain of JE virus (SA-14-14-2). It was first licensed for use in 1988 in People’s Republic of China and current usage is over sixty million doses per year. It is also licensed in India, South Korea and Nepal. This live attenuated vaccine constitutes over 50% of global production of all JE vaccines. Dose is 0.5ml subcutaneously for all ages. Initial studies done with this vaccine demonstrated an efficacy of about 80% with single dose and 98% with 2 doses. However, more recent case control studies from Nepal have shown efficacies of 98.5 % at 12-15 months and 96.2% at 5 years with a single dose of the vaccine.
As per recent WHO reports and as recent Cochrane meta analysis no serious adverse effects have been reported with this vaccine.
In 2005 India witnessed a massive outbreak of JE which resulted in 2000 deaths and even greater disability. In response to this outbreak the Government of India with support of Program for Appropriate Technology in Health (PATH) initiated a pilot project in 2006 of immunizing children in hyperendemic districts against JE. 7 districts in UP, 2 in Assam and one each in West Bengal and Karnataka were targeted. SA-14-14-2 live JE vaccine manufactured by Chengdu institute of Biological Products, Chengdu, China was used.
It was given
in a campaign mode to children aged 1-15 years as a single
subcutaneous dose using autodisable (AD) syringe. Eleven
million children were targeted as beneficiaries and 9 million
children actually received the vaccine, i.e. nearly 86% of the
target was achieved. UP recorded 96% coverage against all
expectations. There were 504 adverse effects following the
campaign of which 482 were minor adverse effects. 22 deaths
were reported but none were causally related to the vaccine
as cleared by an expert committee set up to monitor the adverse
effects. This project reached 20 million children in 2007 and
aims to reach 20 million more in 2008.