Hepatitis B immunization coverage and risk behaviour among Danish travellers: Are immunization strategies based on single journey itineraries rational?
Introduction
Vaccines against hepatitis B have been available for more than two decades, and universal immunization against hepatitis B has been recommended by WHO since 1997.1 However, several low incidence countries including Denmark have chosen a selective vaccination strategy, based upon individual risk evaluations made by health care professionals. The disease burden in Denmark is not overwhelming, with approximately 5 new reported cases of chronic hepatitis per 100,000 population per year (all exposures included).2
The United Nations World Tourism Organisation reports a 100% increase in the number of international tourist arrivals since 1995.3 As the travel frequency increases, the individual lifetime risk of exposure to vaccine preventable diseases increases as well. The question is then, do national guidelines protect the travellers sufficiently, and is the current strategy rational?
Danish hepatitis B immunization recommendations are based not only on the travel destination, but also on journey length and presumed on-travel risk behaviour. Thus, a prerequisite for the risk evaluation is a thorough interview and knowledge on the worldwide distribution of high-, medium- and low-endemic areas. In real life, the health care professionals do not always ask in great detail about intentions of sexual risk behaviour, tattoos or other voluntary risk behaviour. Therefore, the advice is often based on journey length and destination alone. One might imagine that this practise misclassifies some high-risk travellers who then end up travelling nonimmune. On top of this, some risk situations are involuntary and unforeseeable such as accidents leading to hospitalisation etc. Finally, approximately fifty percent of travellers do not seek pre-travel medical advice at all.5, 6, 7
Thus, it seems there are many potential pitfalls and obstacles on the road to an effective selective vaccination strategy.
The purpose of this study was to determine how the Danish selective vaccination strategy works in practise; the study is part of a series of studies describing pre-travel preparations, on-travel behaviour and post-travel disease rates among Danish travellers.
Section snippets
Materials and methods
An Internet based cross-sectional survey was conducted by Zapera from 25th of June to 17th of July 2007 via an Internet based panel consisting of 41,500 Danes aged 18–79 years. Zapera is an Internet based Market Research Institute. It complies with the standards and best practises formulated by the European Society for Opinion and Marketing Research (ESOMAR).4
26,640 persons from the panel were invited to join the survey. They were representative of the general population regarding gender, age
Results
Of the 11,688 respondents, 1090 had travelled to hepatitis B endemic areas outside Europe within the previous 12 months. Their average journey length was 23 days. The respondents were 18–79 years old and representative of the general Danish population regarding age. Therefore it was possible to make a rough estimate of the average cumulative stay in endemic areas for an adult Dane: 23 days • 9.3% per year • (79–18) years = 131 days = 4.3 months spent in endemic areas from the age of 18 till 79.
Discussion
The purpose of this study was to determine if the selective vaccination strategy is rational and effective:
- 1.
Is it rational to base risk stratification on itinerary and presumed risk behaviour on single journeys?
- 2.
Does the risk stratification system work in practise, i.e. are the guidelines followed?
The answer to the first question is both ‘Yes’ and ‘No’. The rationale of the guidelines, i.e. basing the risk evaluation on journey length and presumed on-travel risk behaviour, is both supported and
Conclusion
The data show that risk stratification systems based on single journey itineraries and presumed risk behaviour are not rational. Firstly because the average cumulative lifetime stay in endemic areas is high enough to warrant immunization in itself. Secondly, most risk situations occurred on short-term journeys, and the majority of risk situations were involuntary and thus would not come to light in a pre-travel counselling session.
These results together with the availability of vaccines with
Acknowledgements
The survey was initiated and funded by GlaxoSmithKline (GSK) who used the results for internal purposes. Raw data were then handed over to the authors to use freely. GSK has not had any influence on the analysis, interpretation or publication of results.
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