The Burden of Japanese Encephalitis in the Philippines: How to Prevent it?

Sanofi Pasteur recently held a press briefing in Dusit Thani about the growing number of cases of Japanese Encephalitis (JE) here in the country. Dr. Lulu C. Bravo of Philippine Foundation for Vaccination and Dr. Cynthia Alcantara-Aguirre of Philippine Society of Microbiology and Infectious Disease headed the briefing.

JE is now present in 24 countries and it is a leading cause of viral encephalitis in Asia. It is transmitted by the mosquito vector Culex Tritaeniorhynchus. The virus can cause inflammation of the brain, leading to high fever, headache, fatigue, vomiting, confusion, and in severe cases, seizures, spastic paralysis, and coma.

Unlike other virus-carrying mosquito, the Culex Tritaeniorhynchus likes to lay egg on clean water. There is no specific treatment for this disease. JE is fatal in 20 to 30% of cases and among those who survive, 30 to 50% suffer from permanent disabilities.

The first case of JE in the Philippines is back in 1982, somewhere in Nueva Ecija. Data from the Department of Health (DOH) Epidemiology Bureau revealed that for 2016, among 875 acute meningitis-encephalitis suspected cases reported as of August 2016, 119 (14%) were laboratory-confirmed for JE.

Currently, the highest number of confirmed JE is recorded in Region III (Nueva Ecija, Pampanga and Tarlac) followed by Region II (Cagayan, Isabela and Nueva Viscaya) and Region XI ( Compostela Valley, Davao del Sur and Davao Oriental.)

JE usually occurs in rural and agricultural areas, however, an epidemiological study conducted by Dr. Anna Lena Lopez of the National Institute of Health (NIH) published in 2015, showed that the virus circulates in all regions of the country, including Metro Manila.

The study showed that although majority of cases occur in children younger than 15 years of age, adults remain at risk, with 15% of cases occurring in individuals older than 18 years.

As part of the Philippine government’s strategy to reduce mosquito-borne diseases, the 4S program was implemented several years back. 4S stands for: Search and destroy mosquito breeding places, use Self-protection measures, Seek early consultation for fever lasting more than 2 days, and Say yes to fogging when there is an impending outbreak. However, mosquito-borne diseases are still on the rise. According to the WHO, the most effective way of reducing disease burden is vaccination against the illness.

The WHO cites that there is clear evidence demonstrating the impact JE vaccination has on disease burden in a population. Hence, the WHO has recommended that JE vaccination be integrated into national immunization schedules in all areas where JE is recognized as a public health problem. The WHO Global Advisory Committee on Vaccine Safety (GACVS) has reviewed data on the different types of JE vaccines (inactivated and live attenuated vaccines) and has found them to have acceptable safety profiles. Local scientific bodies, including the Philippine Pediatric Society (PPS) and Pediatric Infectious Disease Society of the Philippines (PIDSP), have recommended that JE vaccination be given as a single primary dose for those 9 months old and above. 

 For individuals less than 18 years of age, this should be followed by a booster dose 1 to 2 years after. Other preventive strategies for disease control include bed nets, repellents, long-sleeved clothes, coils, vaporizers and mosquito control measures.

About the Vaccine

The JE-chimeric vaccine, a live attenuated recombinant vaccine, was first licensed in the Philippines in 2013. The vaccine is produced by Vero cell culture, a cell culture technology recommended by WHO. It is the only JE vaccine available locally and is approved for use for individuals 9 months old and above, with high immunogenicity rates.