Japanese encephalitis B vaccination

There are currently one vaccine for use in the UK. The vaccine is inactivated and do not contain live organisms so cannot cause the disease against which they protect (1)

• IXIARO
• licensed in the UK for individuals aged two months and older
• an inactivated vaccine produced in Vero cells and adsorbed onto an adjuvant of aluminium hydroxide to prove its immunogenicity
• available as a 0.5ml suspension in a pre-filled syringe (Type 1 glass) with a plunger stopper (chlorobutyl elastomer).
• given by intramuscular injection
  • however, for individuals who have a bleeding disorder, IXIARO should be given by deep subcutaneous injection to reduce the risk of bleeding
• can be given at the same time as other travel or routine vaccines
  • the vaccines should be given at a separate site, preferably in a different limb
  • if given in the same limb, they should be given at least 2.5cm apart
• should be avoided during pregnancy or lactation as a precautionary measure
  • as a precautionary measure, administration of IXIARO during pregnancy or lactation should be avoided
    • however, travellers and their medical advisers must make a risk assessment of the theoretical risks of JE vaccine in pregnancy against the potential risk of acquiring JE
    • miscarriage has been associated with JE virus infection when acquired in the first two trimesters of pregnancy

Dosage and schedule of JE vaccines are as follows:

A rapid schedule administered at days 0 and 7 is also licensed for adults aged 18-64 years of age. Antibody responses are non-inferior to those of the standard vaccination schedule (1)

For children (from two months of age) and adults 65 years of age and older

• although not licensed for these age groups due to lack of data, the rapid schedule can be used in circumstances where there is genuinely insufficient time to complete the standard schedule prior to travel
• no data to suggest that the rapid schedule would be harmful for these travellers

A booster dose (third dose) should be given

• within the second year (i.e. 12-24 months) after the two-dose primary immunisation series and prior to potential exposure to Japanese encephalitis virus.
• at 12 months after primary immunisation to individuals at continuous risk of acquiring JE, e.g. laboratory personnel and long-term travellers who expect to reside in JE endemic areas for appreciable periods of time (1)

For travellers:

• JE vaccine is recommended for those who are going to reside in an area where JE is endemic or epidemic
• travellers to South and South-East Asia and the Far East should be immunised if staying for a month or longer in endemic areas during the transmission season especially if travel will include rural areas
• other travellers with shorter exposure periods should be immunised if the risk is considered sufficient e.g.- those spending a short period of time in rice fields (where the mosquito vector breeds) or close to pig farming (a reservoir host for the virus) should be considered for vaccination (1)

Check uptodate details in the The Green Book before prescribing/administering an JE vaccination.

Check the Summary of Product Characteristics (SPC) before prescribing/administering a JE vaccine.

Reference:

• (1) Immunisation Against Infectious Disease - "The Green Book". Chapter 20 Japanese encephalitis (April 2019)