Predictors of travel-related hepatitis A and B among native adult Danes: a nationwide case-control study.

OBJECTIVES: To assess journey length and other predictors of travel-related acute hepatitis A (HAV) and B (HBV) virus infection among native Danes and determine the sensitivity and specificity of current pre-travel vaccination guidelines.

METHODS: A nationwide case-control study was perfomed involving 60 Danes with HAV and 14 with HBV who acquired hepatitis in non-western countries from 2000 to 2010. Non-immune travellers from a nationwide survey (1188 HAV and 1709 HBV) served as controls.

RESULTS: The odds ratios (ORs) for HAV and HBV increased with increasing journey length (p<0.0001). However, 90% of HAV and 62% of HBV cases travelled for less than 4 weeks, and the daily infection rate did not increase with journey length; rather, for HAV it decreased. Increasing age (p<0.0001) and journeys to Africa (OR 6.1 (3.2-11)) raised the risk of acute HAV. Travelling alone or with friends as compared to travelling with a partner/family (OR: 15 (3.2-134)) strongly predicted HBV risk. Danish vaccination guidelines had HAV/HBV sensitivities of 86%/31%, and specificities of 27%/95%, respectively. Incidence rates were 12.8 (HAV) and 10.2 (HBV) per 100,000 non-immune travel months, and acute disease severity affected HAV and HBV cases equally.

CONCLUSIONS: These results may support revision of current pre-travel vaccination guidelines.