TBE vaccine – are you still protected?

Many people only start thinking about it when spring comes – the vaccination card is somewhere in a drawer, but the memory of when the last TBE injection was taken is blurry. At the same time, exposure to ticks increases when work, exercise and outdoor activities move into nature. Then the question becomes concrete – is your TBE vaccine still effective, or is it time to top up?

Is your TBE vaccine still effective? Antibodies may provide part of the answer

TBE, tick-borne encephalitis, is caused by a virus that can cause everything from fever and headache to encephalitis with long-term neurological problems. There is no specific treatment once the disease has developed, which makes preventive protection particularly valuable. Vaccination is therefore the most important medical measure for people who live in or regularly visit Swedish risk areas.

The vaccines used in Sweden generally provide good protection, but the protection is not static. How long it lasts depends on factors such as age, number of doses taken, time since the last dose and whether the immune system is functioning normally. It is therefore not uncommon for people to wonder if a antibody test can show whether the vaccination is still providing protection.

What does it mean that the TBE vaccine “still has an effect”?

When you say that a vaccine is effective, you mean in practice that the immune system can still recognize the virus and react quickly enough to reduce the risk of developing the disease. For TBE, this is often measured indirectly through antibodies, i.e. proteins that the immune system forms after vaccination or after an infection. Antibodies can be analyzed in blood tests, but they are only part of the immune system.

There is an important medical caveat for TBE in particular: there is no fully standardized, individually safe limit that says that “above this level you are protected” and “below this level you are unprotected”. Research and international evidence show that neutralizing antibodies are associated with protection, but the relationship is not so precise that a single routine test can replace the vaccination schedule. Immune responses from memory cells can also contribute, even when antibody levels have declined.

This means that the answer to the question “is my TBE vaccine still working?” usually starts with the vaccination history, not with the laboratory. If you have followed the recommended schedule, the likelihood is high that you have good protection, especially if you are younger and have a healthy immune system.

When can antibodies still be a reasonable way to get guidance?

For most healthy people, antibody testing is not needed after a correctly administered vaccination. Official recommendations are instead based on the number of doses and the interval between doses, as this is the most practical and medically reliable way to maintain protection in the population. Individual antibody measurements are generally not recommended after regular vaccinations, except in special situations.

There are still situations where a blood test can be valuable as a complement. This applies in particular to people with suspected or known impairment of the immune system, for example after organ transplantation, in certain blood diseases, during immunosuppressive treatment or after stem cell transplantation. In such groups, the immune response to vaccines may be weaker or more difficult to assess, and serology can sometimes help the doctor plan further treatment.

Another typical scenario is someone who does not know which doses have been taken. Perhaps there is no vaccination card left, perhaps doses have been taken at different clinics over many years. In this case, antibodies can sometimes provide pieces of the puzzle, but the test result must be interpreted with caution. A positive result does not prove exactly how long the protection lasts, and a low or difficult-to-interpret value does not automatically mean that the vaccination “failed”.

Who is at risk of losing protection faster?

As you get older, you are at risk of losing protection faster. This is because the immune system, on average, responds less effectively to vaccination the older we get, and studies show that levels of antibodies tend to decline faster in older people than in younger adults. This is an important explanation for why people who receive their first doses after the age of 50 need a more frequent schedule than younger adults.

According to the Public Health Agency's recommendations from 2026, adults aged 18–49 and children from the age of 3 normally receive three doses in the basic vaccination. The first booster dose is given 3 years after the third dose. People who have received at least four doses before the age of 50 are then recommended to receive booster doses every 10 years. For people who have received any of their first four doses after the age of 50 and for people with a compromised immune system, continued boosters every 5 years after dose 5 are recommended instead.

There is also an important detail that many people miss. In order to comply with the 10-year interval between booster doses, it is required that at least four doses of TBE vaccine have been received before the age of 50. If the fourth dose is not given until after the 50th birthday, continued booster doses every 5 years are recommended instead, in the same way as for people who start vaccination after the age of 50 or have a compromised immune system. This can have a significant impact on assessing whether your vaccine protection is still up to date.

Even with correct vaccination, so-called breakthrough cases can occur, i.e. TBE despite the person having been vaccinated. They are uncommon, but are seen more often in the elderly and in people with other risk factors. This is another reason not to rely on old doses for too many years if you continue to be exposed to ticks.

What does an antibody test mean in practice?

If a blood test shows antibodies to TBE, it indicates that the immune system has reacted to the vaccine or previous infection. It is often reassuring, but not definitive proof of complete and long-term protection. The level in the test must be put in relation to your age, vaccination history and any diseases or medications that affect the immune system.

If, on the other hand, the test shows low or difficult-to-interpret levels, the next step is rarely to speculate, but rather to compare the result with the recommended schedule and assessing the need for a booster dose. For a healthy 35-year-old who has taken all doses according to plan, an isolated serological value is often less useful than knowing when the last dose was given. For a 67-year-old with immunosuppressive treatment, the same test result may be more relevant, since the probability of a weaker vaccine response is higher.

It is also good to know that different laboratory methods are not always directly comparable. This means that antibody tests for TBE should primarily be seen as a a tool to support medical decision-making in the right context, not as a simple “yes or no” marker for the public.

When should you check your protection before the season?

The most concrete check is often to review when you took your doses. If you stay in forests, tall grass, summer cottage areas or work outdoors in parts of Sweden where TBE occurs, you should not wait until after the first tick bite to review your protection. The Public Health Agency recommends vaccination for people at risk of tick bites in areas with moderate or high incidence, and also certain people with a weakened immune system in large parts of Sweden south of the Dalälven River and adjacent areas.

Following up on vaccine protection before the season is important and a review is particularly important if any of the following is true:

• you do not remember when the last TBE dose was taken

• you have turned 50 since the vaccination series began

• you are using medications that suppress the immune system

• you have undergone transplantation, cancer treatment or other care that can affect the immune response

• you are planning a season with a lot of time spent in a risk area

In most cases, a review of vaccination history is sufficient to determine the next step. In more complicated cases, antibody testing can provide additional information, but it should be interpreted as part of the whole, not as a stand-alone answer.