Abstract

Background - Disease morbidity of tick-borne encephalitis (TBE) has been increasing over the last decades. Since the 1990s, however, no extensive seroprevalence studies on TBE in humans have been performed in Switzerland. Here we assessed the prevalence of anti-TBE virus (TBEV) antibodies among different groups of the Swiss blood donor population.
Materials and methods - The study was carried out from July 2014 to January 2015. Blood donors participating in the study (n=9,328) were asked to fill in a questionnaire relating to vaccination against or infection with different flaviviruses, and blood samples were collected. All samples were screened for the presence of anti-TBEV IgG antibodies using ELISA testing. Seropositivity rates in different groups of blood donors were compared using Chi square tests with Bonferroni correction.
Results - In 2014 and 2015, 24.6% of healthy Swiss blood donors indicated vaccination against TBE. Among vaccinated blood donors, antibody prevalence was significantly higher in younger (<40y: 85.3%) than older individuals
(≥40 to <55y: 80.0%, ≥55y: 76.7%; p=0.005). In non-vaccinated individuals, antibody prevalence was significantly higher in younger (<40y: 10.0%) than older (≥40 to <55y: 4.0%, ≥55y: 3.9%; p<0.005), male (6.8%) than female (3.7%, p<0.0001), and blood donors from endemic (7.0%) than border (6.2%) or non-endemic regions (4.2%, p<0.001). Possible asymptomatic infection, as defined by positive IgG ELISA results in blood donors indicating no vaccination against TBEV, was found in 5.6%.
Discussion - Our data importantly complement the knowledge on TBEV vaccination rates and estimate the frequency of subclinical TBE in Switzerland.

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Authors

Rahel Ackermann-Gäumann - Spiez Laboratory, Federal Office for Civil Protection, Spiez, Switzerland; Swiss National Reference Centre for Tick-Transmitted Diseases, Spiez and La-Chaux-de-Fonds, Switzerland

Claudia Eyer - Interregional Blood Transfusion SRC, Bern, Switzerland

Michael Vock - Institute of Mathematical Statistics and Actuarial Science, University of Bern, Bern, Switzerland

Peter Gowland - Interregional Blood Transfusion SRC, Bern, Switzerland

Caroline Tinguely - Interregional Blood Transfusion SRC, Bern, Switzerland

Stephen L. Leib - Institute for Infectious Diseases, University of Bern, Bern, Switzerland

Mauro Bori - Blood Transfusion Service SRC della Svizzera Italiana, Lugano, Switzerland

Andreas Buser - Blood Transfusion Service Beider Basel, Basel, Switzerland

Stefano Fontana - Interregional Blood Transfusion SRC, Bern, Switzerland; Blood Transfusion Service SRC della Svizzera Italiana, Lugano, Switzerland; Faculty of Biological Medicine, Lausanne University Hospital, Lausanne, Switzerland

Jutta Thierbach - Blood Transfusion Service SRC Nordostschweiz, St. Gallen, Switzerland

Tina Weingand - Blood Transfusion Service SRC Zentralschweiz, Luzern, Switzerland

Christoph Niederhauser - Interregional Blood Transfusion SRC, Bern, Switzerland; Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Faculty of Biological Medicine, Lausanne University Hospital, Lausanne, Switzerland

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