Infectious disease epidemiology – the Danish experience

During the 22nd EHFG, Young Gasteiners Durdica Vukic Marosevic and Bélène Podmore had the opportunity to sit down with Tyra Grove Krause, the Head of Department of Infectious Disease Epidemiology and Prevention at Statens Serum Institute (SSI) in Denmark. The main duty of SSI is to ensure preparedness against infectious diseases and biological threats as well as control of congenital disorders. This includes research with over 400 publications a year, disease surveillance, special diagnostics, the maintenance of the Danish National Biobank, as well as the responsibility for vaccine supply in Denmark. They wanted to get some insights on how the Danish surveillance system for infectious diseases works, whether the Danish colleagues use big data and – following the theme of the 2019 EHFG conference – what Tyra perceived disruption to be.

Tyra Grove Krause, the Head of Department of Infectious Disease Epidemiology and Prevention at Statens Serum Institute (SSI), Denmark

Durdica Vukic Marosevic and Bélène Podmore (DVM & BP): Can you tell us a little bit about your background?

Tyra Grove Krause (TGK): After finishing my medical studies, I did a Ph.D. in Epidemiology at SSI, and I actually worked on allergic diseases in Greenland and through that, I got interested in infectious diseases. My initial plan was to become a dermatologist, but then I came to the department where I am working now and it’s the best job you can have! You have the routine work with data collection, data analysis and the communication of data but you also have the opportunity to do research and long-term projects to improve our surveillance system. I really appreciate the international collaboration and the whole idea of not only working with patients individually, but rather with health promotion and prevention with larger groups. There is also a lot of interest in what we do by the media and politics and if you learn how to communicate and work with the political level, you can really make an impact with your knowledge. That’s why I specialised in public health medicine.

DVM & BP: At the political level how receptive are policymakers of your input?

TGK: They want the input from experts, and sometimes we are not good enough at pointing out what is important and communicating that effectively. If we practiced that, I think we could have even greater success stories. For example, once the political level heard rumours and concerns about vaccine hesitancy, they wanted to make vaccination mandatory and asked how to roll that out. We said that it was not the right way forward from a scientific perspective, that there are a lot of reasons why children are not being vaccinated and we proposed alternative initiatives that may increase vaccination coverage instead of a mandatory vaccination policy. A large proportion of our initiatives received funding in the end. Such as an electronic vaccine reminder system for parents developed at the national level in order to improve vaccination coverage. Another initiative involved district nurses who visit new parents and educating and empowering them to be vaccination ambassadors. They were trained in how to talk to the parents about this topic and support them with their decision. The district nurses also received access to the vaccination registries so they can check to see whether children have received the vaccination. If not, they could talk to the parents and address their concerns directly.

DVM & BP: How far along are you with the implementation of this vaccination reminder system?

TGK: We have had a system in place since 2014 and it works like this: When a child turns 2, 6 ½ and 14 years old, the system automatically checks their vaccination status to see if they have missed any vaccinations. If so, an electronic letter is sent to both parents’ e-boxes. All communication from public authorities goes through this type of personal password-protected e-box. This is the main way for authorities to communicate with citizens on a personal level. Vaccination reminders are also sent through the GP app ‘My Doctor’. This initial reminder system lead to an increase in coverage of MMR vaccination (measles-mumps-rubella) of 5 percentage points. This year we are going to extend this system to send reminders to parents two weeks before the date of the recommended vaccination schedule is due, and then we will follow up one month after, to check whether the children received the scheduled vaccination and remind the parents if they didn’t.

DVM & BP: Can you tell us a bit about the datasets you work with?

TGK: We have had our surveillance system based on reports from primary care physicians (PCPs) and hospital doctors on mandatory notifiable diseases and datasets from laboratories for those diseases, which are under laboratory surveillance. As the reporting rate is quite low for some diseases and important information was often missing, we realised we had to change that system, and now the mantra is not to ask the physician for information that is already registered elsewhere. In order to reduce the workload on PCPs and to increase our data quality, we need to capture data from existing registries (hospital discharge registries, vaccination registries, death certificates, etc.). This is possible via the social security number (unique personal identifier) that is used for every contact you have with the health care system. So, we have created a microbiology database with all laboratory test results as the core of our surveillance system and aim to link it with other available registries.

For instance, we use it for influenza surveillance now, to see whether patients diagnosed microbiologically with influenza have been hospitalised, received Intensive Care Unit (ICU) treatment and whether they have any underlying illnesses based on previous diagnoses, vaccination status, etc. For some diseases, you still need data that is not available in the registries (for example sexual behaviour or detailed travel information). For these, you will still need active reporting and information directly from the physicians. If we detect a laboratory-confirmed case of a mandatory notifiable disease, we send a notification to the physician to fill out an electronic form but only for the information we are missing. We already have information on whether the patient is hospitalised, has an underlying illness, their vaccination status and previous test results that we can get from the registries. Currently, the form is sent in paper format and is not automated but early next year it will become electronic and we hope to link it to the existing microbiological database and automate it.  

We haven’t received funding to develop the whole system at once so it has been built up piece by piece. For now, the influenza surveillance works fine with linkage to all registries, but we haven’t done that yet for other pathogens. That is still in the pipeline.

DVM & BP: Do you use any information from social media?

TGK: Not yet. We do not have a social media monitoring system, but I know that the National Health Authority is considering using social media because they are responsible for communicating the information to citizens. And they did a similar campaign focused on information on HPV vaccination as was done for the HPV crisis in Ireland.  

DVM & BP: Do you see any benefit of using social media for infectious disease surveillance?

TGK: Yes! As an example, during the HPV crisis in Denmark there were suddenly reports of potentially severe side effects on social media and television programmes, which led to a huge decline in vaccine coverage. In this situation, you need big data and social media information to detect that there is concern. After that, you need to follow up with large-scale epidemiological studies to examine the hypothesis. One study that was done, and which is about to be published, is where we used machine learning to identify health service contact patterns of the girls who were vaccinated and reported side effects. This contact pattern could be used as an outcome to compare differences between vaccinated and unvaccinated girls. This type of analysis is too complex for classical epidemiology and this is where big data and machine learning can be beneficial for infectious disease research. At our institute, we also did a case-control study comparing those who had side effects and controls who were vaccinated but didn’t report side effects, and you could see that they had different contact patterns before their first vaccination. The girls with side effects had more contact with their GPs and psychological support even before HPV vaccination, compared to those who didn´t report side effects.

What is clear is that you need to do the studies, but you also need to respond to the crisis by informing the public. A good example are social media campaigns. Throughout the whole process, you need to use big data to detect there is a problem, to confirm or to analyse the problem and to communicate you need social media. We have a lot of information on our website, but interviews with focus groups revealed that the regular parent does not go to our website to get the information, so we need to be there where the people are, and communicate on social media.

DVM & BP: Relating to communication, how in your experience do you think it best to communicate your findings?

TGK: I think it is very difficult to communicate emotions to the public. I am a medical epidemiologist – I like to communicate the data because that is what I am an expert in, but you have to balance the emotions with the brain. You have to use both tools when you communicate.

DVM & BP: From your experience, how do you think it is best to present data effectively to policymakers?

TGK: The politicians are interested in economics. We need to explain, how many cases we can prevent and what are the cost-savings if they are prevented. To the citizens, we need to communicate numbers, which are understandable. They don’t understand the concept of 1% risk or 50% effectiveness. You have to mention how many people die from this disease every year and how many deaths you could prevent if you vaccinate or something like that to make it tangible. We do not communicate much with the public – that is the role of the national health authority.  We communicate more with healthcare providers.

DVM & BP: What is the challenge of communicating with healthcare providers?

TGK: In the case of healthcare-associated infections (HAI) we have underestimated the challenge of communicating data to the hospital departments and make them use the data. It was easier to see an impact and change on the local level with point prevalence studies because the teams would go out to the departments, and they would allocate staff to do a survey, look at the medical records, have a dialogue with the staff and discuss the results with them.

The data collected in real-time from the surveillance system for HAI is not used as effectively as the point prevalence studies and the question is: How do we go from the collection of data to the implementation of the knowledge at the local level? We need to move into social sciences and maybe other disciplines to determine how we can get the information out and used more effectively.

DVM & BP: Regarding the theme of the EHFG 2019 conference of a “healthy dose of disruption” – do you think there is anything that has been disrupted in infectious disease epidemiology or is there something you want to be disrupted?

TGK: I think that the biggest disruption for us was the development of a central, national microbiology database. That was a challenge. Before that, every laboratory considered their data as being their own. Eventually, we argued that in order to improve patient care it is beneficial to see and obtain the test results generated in another region, and not to duplicate test results. Also, the value for public health surveillance of having one centralised database as we’ve already discussed with the example of influenza. And to resolve the concerns about publishing research, it was decided to have a steering group with representatives from all laboratories that decides on each research project and ensures there is an author from each laboratory on each research publication. That was a big step!

Somehow, there is still this idea of ownership of data, which is pervasive. We have a public health system and I think the data that we generate in this public health system should be open for all who can use it to improve public health. That is important and is in everybody’s interest. Of course, the data has to be safeguarded, and assurances need to be made that the data is not misused. But, I think this is still something that needs to be disrupted – the access to data, and the whole concept that when you collect data in the health system it is not something you own.

This interview was conducted by Young Gasteiners Durdica Vukic Marosevic (DVM) and Bélène Podmore (BP).

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