TBE (Tick-Borne Encephalitis)

TBE, also known as Central European encephalitis, is caused by a virus from the flavivirus family. TBE virus is transmitted to humans through tick bites.

TBE virus is widespread in Scandinavia, the Baltics, Russia and Siberia, in the Balkans, in certain parts of Germany and Austria.

In Denmark, most cases have been associated with stays on Bornholm, where the TBE virus and the disease have occurred for over 50 years, but since 2018, cases have also occurred outside Bornholm, especially in Tisvilde Hegn and a few other places in North Zealand, see information further down the page.

TBE occurs in so-called microfoci, which are small, demarcated areas, such as a meadow or clearing by a stream where animals drink. This is in contrast to Borrelia, which can be found in ticks in an entire forest.

Vaccine contents:

The vaccine contains inactivated TBE virus.

Who should be vaccinated?

Children over 1 year of age and adults with work or long-term residence in local areas where the disease is found.

Therefore, if you regularly travel in a known risk area outside paths in vegetation, where deer, and thus the concentration of ticks with potential TBEV infection, may be high, you may want to consider getting vaccinated. This could include hunters, campers, mushroom pickers, orienteers, forest workers and summer house owners. Outside Denmark, the TBE risk areas are typically Scandinavia with the Baltic countries, and especially the central parts of Europe, such as Poland, Germany and Austria.

Vaccination dose:

A basic vaccination consisting of several doses is given at different intervals, and revaccination may be necessary.
The child dose is used in the age group 1 to 15 years, from 16 years the adult dose is used.

To achieve immunity before tick activity begins in the spring, it is recommended to give the first and second doses during the winter months. These doses should be given 1-3 months apart. If a rapid immune response is required, the second dose can be given two weeks after the first dose. The third dose should be given between 5-12 months after the second vaccination. If the recommended interval between vaccinations is exceeded, the vaccination series is completed. There is no need to start over.

In cases where the vaccine that has been started (either Encepur or Ticovac) cannot be obtained within a reasonable period of time, taking into account the normal vaccination schedule, i.e. corresponding to 3 months between the 1st and 2nd doses and 12 months between the 2nd and 3rd doses for both vaccines, and for both the child and adult doses, in this shortage situation, the vaccination series can be completed with the other TBE vaccine that is available. However, efforts should be made to give the first two doses with the same product.

This guidance on a vaccination programme (both primary and booster vaccination) that has started with one of the vaccines and is completed with the other vaccine applies to both vaccine products, taking into account the different age limits for use of the child dosage. However, it does not apply to the Encepur express programme, where Encepur must be used for all four vaccinations.

The above recommendation on cross-vaccination is a Danish recommendation in addition to what is mentioned in the summary of product characteristics. The same recommendation is used in other European countries during periods of shortage of TBE vaccines.

Who should not be vaccinated?

In case of acute illness or fever, vaccination should be postponed.
People who have had serious side effects from previous vaccination with the vaccine.
People with severe allergies to one or more of the ingredients.
People with an allergy to eggs should be referred to a specialist allergology department, as the vaccine can cause a serious allergic reaction.

Caution should be exercised when vaccinating individuals with known neurological disorders.
If in doubt, please consult your doctor.

Pregnancy and breastfeeding:

The vaccine should only be used in pregnant and breastfeeding women if there is a clear need and only after careful assessment of potential risks and benefits.

Most common side effects:

Redness, swelling and tenderness at the injection site, headache, nausea, muscle pain, malaise and fever.

Duration of protection:

After completing the primary vaccination course, usually with 3 doses, 3 years of protection are achieved. The first booster is therefore given 3 years after completing the primary vaccination course. If revaccination is still needed, a booster vaccination is recommended every 5 years for people over 16 years of age but under 60 years of age, and every 3 years for people over 60 years of age.
If revaccination is required, see the product summary.

Symptoms:

Once infected, the infection is asymptomatic in approximately 75%. In the remaining 25% who develop symptoms, the disease will most often manifest itself in two phases. After an incubation period of 7-14 days after the tick bite, the first phase occurs with 2-7 days of uncharacteristic, flu-like symptoms such as fever, muscle aches, fatigue and headache. Between one and two thirds will, after a symptom-free period of between a few days and up to 3 weeks, develop infection of the central nervous system (encephalitis), with symptoms such as new fever, headache, convulsions, unilateral paresis, impaired consciousness and personality changes.

There is no treatment for TBE virus infection. About 1/3 of patients with CNS symptoms may develop years-long or permanent neurological damage in the form of paralysis, hearing loss, tremors and/or cognitive dysfunction such as learning disabilities and paranoid delusions.

Transmission routes:

TBE virus is transmitted through the bites of ticks found in forests and grassy vegetation. It occurs in perennial microfoci (small, delimited areas the size of a bush or a handball court). The reason for the highly variable and uneven incidence limited to microfoci is not clearly understood. Therefore, there may be large differences in risk in different areas within the same country.

TBE virus can also be transmitted via infected unpasteurized goat milk and cheese.

The virus is found in deer and mice as well as domestic animals, such as cats, and can be transmitted to ticks when they bite and suck the animals' blood. The tick can then transmit the virus to humans with a new bite. Human-to-human transmission does not occur. TBE virus transmission by tick bite starts within minutes from the tick's salivary glands and lasts for hours, which is why the tick should be removed as soon as possible as soon as it is discovered.

Hunters and others who spend a lot of time in nature in the specific areas where TBE is found are at greatest risk of infection.

Prevention:

TBE can be prevented by vaccination of children and adults. The risk of developing symptomatic CNS infection increases with age. This applies especially to men over 50 years of age. Therefore, if you regularly travel in a known risk area outside paths in vegetation, where deer, and thus the concentration of ticks with potential TBEV infection, is high, you may want to consider getting vaccinated. This could include hunters, campers, mushroom pickers, orienteers, forest workers and summer house owners. Outside Denmark, the TBE risk areas are typically Scandinavia with the Baltic countries, and especially the central parts of Europe, such as Poland, Germany and Austria.

The risk of tick bites when walking in forests and scrub can be reduced by wearing boots and long pants and by using certain mosquito repellents that have a deterrent effect on ticks (e.g. Autan, which contains Icaridin).

In addition, you should frequently check the skin for ticks and brush them off or quickly remove them with tweezers, tick remover or just your fingernails from yourself, children and dogs. If the tick has attached itself, it is best removed by grabbing the tick as close to the skin as possible, by the head. Pull it slowly upwards and be careful not to squeeze or crush the tick while doing so. If a bit of the tick remains in the skin, it is not a problem. It will be shed within a few days. In children, it is important to look carefully at the scalp, hairline and behind the ears.

TBE virus is transmitted in minutes, while the borrelia bacterium is transmitted more slowly (over hours), so prompt removal of ticks is important.

Diagnostics:

Samples from spinal fluid and blood are sent to a laboratory for analysis (measurement of TBE IgM antibodies and detection of TBE virus). Since serum IgG antibodies to other flaviviruses, e.g. after vaccination against yellow fever, Japanese encephalitis or previous infection with Dengue, can cross-react partially, anti-TBEV IgG titer increases in two consecutive serum samples are also examined as well as possible IgM anti-TBEV in spinal fluid. Specific antibodies can also be confirmed by virus neutralization test (by appointment).

State Serum Institute (2023), https://www.ssi.dk/vaccinationser/vaccineleksikon/c/fsme-vaccine