You have recently conducted a study on TBE. What was it about?

We’ve done a few studies looking at TBE in Switzerland. We’re mostly interested in vaccination coverage. There are two vaccines approved in Switzerland to prevent TBE. We were interested in how many adults are vaccinated in different parts of the country and what factors might influence whether people are getting vaccinated or not.

We’ve also looked at the effectiveness of the vaccines over time – so how long we can expect that they’ll protect someone.

What have you found out?

We found that about a third of adults in the country are fully vaccinated^[1]. It varies a lot depending on the region. In higher incidence regions, the vaccination coverage is higher as well, which makes total sense. It plays into the whole fact of awareness.

One thing that is a bit frustrating to see is that even though you would expect the incidence to come down in regions with a higher vaccination coverage, we did not find this to be so. This indicates that the coverage is not high enough yet.

Another thing that we found that I feel is very important is that awareness has a very big impact on vaccination – people who aren’t vaccinated report that they don’t feel they have enough information about the disease. This is totally understandable, and I think it shows that TBE is a disease that we need to be talking more about.

People here don’t know how common and dangerous it is. Honestly, I come from a migration background and from a place where there is no TBE. And even though I study infectious diseases, I lived in Switzerland for 2 years before I learned about the disease from my kids’ pediatrician! You can be an educated, intelligent person and simply not know. I want people to understand that it’s never too late to get vaccinated!

^[1] TBE vaccination requires 3 doses within the first year of vaccination and a booster every 10 years after that.

Although, it seems like we get many routine vaccinations without always being entirely sure what they help against because we often do not see these illnesses anymore. Like Polio. Might there than be other reasons for why people don’t get TBE vaccinations?

Another thing that has a strong impact on vaccination coverage is the perceived risk. If you are inside a lot and you don’t have outdoor hobbies, I can see how one does not see a risk for TBE and, therefore, doesn’t get the vaccine.

Understandable. But I have heard from parents whose kids sat down for just a couple minutes in the grass and came back with five ticks. So, they seem to be fast, and the absolute amount of time spent outdoors doesn’t seem like the only factor your risk should be assessed by.

Yes. There are peaks the incidence of Borreliosis and, to some extent, in TBE in younger people, in kids from 5 to 14 years old, and we can assume it is because they spend more time outside.

However, TBE, like most infectious diseases, is more severe in older people. It is not fully understood why, but generally speaking, children and young adults have stronger immune systems and, as you get older, your immune system doesn’t respond as well to infections. This is part of it, there are definitely other mechanisms at the cellular level that play a role and still need to be worked out. The immune system is very complicated and tricky to understand.

What other things did your study show?

Another important finding is that the vaccine effectiveness is surprisingly good. It protects for a really long time. We only need to get a booster every 10 years. However, from our study we found that we really do need to finish the first three doses to get that protection!

Many people only get one dose and don’t continue – but the vaccine is much, much less effective with just one dose. While one dose is better than nothing, it’s absolutely key to finish those first three doses.

Also, if someone was vaccinated with one or two doses years ago, it doesn’t matter – one can just continue with the schedule where they left off and still respond very well to the next vaccination. So again – it’s never too late!

Another thing which is good to know is that it takes time for the protection to develop. To have time to generate a sufficient immune response it is recommended to get the first two doses at the end of the tick season ^[1] which means in winter around November and December. To get the second vaccine before tick season is ideal. About half a year to a year after the first dose you should get the third one and then you are good for the next ten years.

^[1] Ticks become active as soon as it is getting warmer, so tick season is from March to November.

Is there a minimum amount of time after the vaccination after which you have some protection?

Since immune systems are highly complicated and everyone is different, this is really hard to say. Generally, immune responses take around two weeks to a month.

I would say after about a month after your second dose you’ll have generated as much of a response as you’re going to have after that second dose. Then you need to wait for a half a year to a year to get the third one.

This was a national study, but TBE is relevant outside of Switzerland as well and, thus, for travelers. How so? Can you tell us something about TBE worldwide?

The TBE virus is found in both Europe and Asia. The disease can be found as far east as northern Japan, there are many cases in northern China and it’s highly endemic in parts of Russia and in the Baltic states. It’s also now quite a problem in southern Sweden and Finland, in addition to Central Europe (Austria, Czechia, Germany, Switzerland).

It’s really important to consider the type of activities that one will be enjoying while traveling. If you’ll be spending time outside in wooded areas in most of Eurasia, it’s worth considering TBE vaccination.

Also, this is really important for travelers to Switzerland!! As I mentioned, Switzerland is among the highly TBE endemic countries – so we’re already living in one of the greatest risk areas – if you’ll have friends or family visiting and if they’ll be spending time enjoying nature, this is something that is worth bringing up with them.

It makes sense that the ticks are to be found in wooded areas and nature. But I assume that they can also be found in bushes and parks in cities, since there is quite the amount of blood to lure them there. So, “outdoors” includes outdoors in cities.

Yes! Absolutely.

Are you the only group in Switzerland who does TBE research?

No, there a few groups in Switzerland, but there are not a lot of people that study TBE in general. The community of TBE researchers is small and they are located mostly in other TBE-endemic countries. For examples, there are several groups in southern Germany and Austria, which are also endemic areas and have a long history with TBE.

However, in Austria for example, mass vaccination was initiated in the 1980s and since they have been familiar with the issue for an entire generation now, their vaccination coverage is over 80% and, therefore, the incidence is much lower than in Switzerland. We are a bit behind here, but I am confident that we will get there.

Which other running or upcoming research projects would you like to tell us about?

Our last study on vaccination coverage was conducted in 2018. That was the year where we had very many hospitalizations because of TBE, so it was a bad year in that regard. It brought on a lot of media coverage which spiked awareness.

It also triggered the change in vaccination recommendations and cost coverage of the vaccine by health insurances. Since 2019 the TBE vaccines are covered by basic insurance and are recommended in almost every canton.

We plan to do another study on national TBE vaccination coverage soon, hopefully in 2024, to see if those changes had the impact we would hope for.

Another thing we should keep in mind is that not everyone who is exposed to the TBE virus (so bitten by an infected tick) gets really sick. Just think of the range with covid infections. Some people are completely asymptomatic while others have mild to severe symptoms or even develop long covid.

It’s the same with TBE. People can be exposed without even knowing. Because of this, we do not fully understand how common it is.

Therefore, we are currently very interested in understanding how often people are exposed, but maybe just don’t get sick enough to end up in the hospital or to get diagnosed with TBE. We can estimate this by looking at whether or not unvaccinated people have antibodies against the TBE virus.

Right now, we’re working on a study looking at immune responses to the TBE virus in people in Zurich. I think this sort of work is important for helping to get a better idea of how widespread the virus really is. I also think that this can help to improve awareness.

For people to want the vaccine, they first need to be made aware that they are at risk. TBE is a terrible disease, and it can be prevented. It’s important for us to focus on that.

Another disease that is spread by ticks is the just very recently detected Alongshan Virus.

Thank you very much, Dr. Kyra D. Zens!