Tick Borne Encephalitis

Transmission

Transmission occurs through the bite of an infected tick. Peak transmission is in early spring and summer, but can occur all year around. The ticks are found in forested and rural areas. The infection can also be acquired through drinking unpasteurised milk, especially goats milk.

Symptoms

The incubation period for the disease is between 2-28 days. The symptoms and severity depend on the infecting strain. There are three strains; European, Far Eastern and Siberian.

The symptoms of the European strain include-flu like illness with high fever. 30% develop signs and symptoms of meningitis and encephalitis with persisting neurological complications in 10-20%. The death rate from the European strain is around 1%.

The Far Eastern strain gives a more severe and prolonged illness with a mortality rate ranging between 5-20%.

Treatment

There is no specific treatment against Tick borne encephalitis.

Prevention

There is a safe and effective vaccine against Tick borne encephalitis. Additional measures include wearing covered footwear and long trousers and checking regularly for ticks after carrying out any outdoor activities in forested areas, such as hiking, camping or fishing.

The tick borne encephalitis vaccine is between 98-99% effective against the European strains and is also thought to be as effective against other strains. It is an inactivated vaccine containing dead virus.

Inclusions

The vaccine can be given to anyone over the age of 1 year who is at risk of Tick borne encephalitis due to:

• Travel to endemic region during tick season (spring to early Autumn mainly) and involvement in outdoor activities.
• Going to live in an endemic country.

Alternative Schedule – For Both Children and Adults

If there is insufficient time prior to travel to complete all three doses, a rapid schedule can be used. The schedule for this is:

• Dose 1-day 0
• Dose 2-14 days after 1st dose
• Dose 3-5 to 12 months after 2nd dose.

Booster doses

For those at continuing risk, a booster dose is recommended at 3 to 5 yearly intervals.

The vaccine can not be given to individuals with:

• A history of severe allergic reaciton to a previous dose of the vaccine or any of it’s components
• A history of severe allergic reaciton to egg
• Acute illness associated with high fever (greater than 38.5 degrees Celsius).
• Unstable neurological conditions, such as poorly controlled epilepsy.

Pregnancy

There is no specific data on the use of Tick borne encephalitis vaccine in pregnant women. However, the evidence for inactivated vaccines in general do not show any harm to either the mother or foetus from receiving these types of vaccines. Therefore, the vaccine can be administered to pregnant women following a full clinical assessment if the risk of infection is considered to be high.

Breast Feeding

It is not known if the vaccine is excreted in breast milk. However, the evidence for inactivated vaccines in general do not show any harm to the infant from vaccinating breast feeding mothers. Therefore, the vaccine can be administered to breast feeding mothers if the risk of infection is considered to be high.

Common Side Effects

Injection site reactions-pain, swelling and redness.

Fever, nausea, headache and muscle ache can also occur, but are not as common.

Interactions with Other Vaccines

There are no interactions with other vaccines and it can be given at the same time as other travel or childhood vaccines.

1) Is the vaccine safe?

The vaccine has been extensively studied during trails for safety and also post marketing following release of the vaccine. There have been rare cases of seizures associated with high fever following the vaccine. The fever following the vaccine tends to occur in the first 12 hours and resolves after 1-2 days.

2) What does the vaccine contain?

• Human albumin
• Sodium chloride
• Disodium phosphate-dihydrate
• Potassium dihydrogenphosphate
• Water for injections
• Sucrose
• Aluminium hydroxide, hydrated
• Chick protein (egg)
• Trace amounts of latex are found in the vaccine packaging
• Trace amounts of Neomycin and gentamicin (antibiotics)and formaldehyde (a preservative) may be found in the vaccine.

The vaccine does not contain Thiomersal or Gelatin.

3) How effective is the rapid schedule?

Two doses of the vaccine given 14 days apart provides around 90% protection. Therefore, two doses can be administered in travellers who do not have sufficient time before exposure for the conventional schedule. It is important that precautions are taken to prevent bites.