ABSTRACT
An open, uncontrolled single centre study was conducted in the Travel Clinic at the Military Hospital, Brussels. Eighty-eight subjects were recruited who had a primary series of tick-borne encephalitis (TBE) vaccine more than 5 years ago and who never received a booster dose afterwards. Response rate after booster vaccination was very high: 84 out of 88 subjects (95.5%) had neutralizing antibodies on plaque reduction neutralization test and all (100%) had IgG antibodies on ELISA, on Day 21-28 after booster vaccination. This study adds valuable information to the common situation of delayed booster interval. The results of our study indicate that in young healthy travellers (<50 years), one booster vaccination after a primary series of TBE vaccine in the past is sufficient to obtain protective antibodies, even if primary vaccination is much longer than the recommended booster interval of 5 years.
Subject(s)
Encephalitis Viruses, Tick-Borne/immunology , Encephalitis, Tick-Borne/prevention & control , Immunization, Secondary , Outcome Assessment, Health Care , Viral Vaccines/immunology , Adult , Belgium , Enzyme-Linked Immunosorbent Assay , Female , Hospitals, Military , Humans , Immunization Schedule , Male , Middle Aged , Military Medicine , Neutralization Tests , Travel MedicineABSTRACT
Tick-borne encephalitis (TBE) is a zoonotic disease, transmitted mainly by the bite of ticks. The TBE virus (TBEV) belongs to the family Flaviviridae, genus Flavivirus and is able to cause meningoencephalitis. For serological TBEV detection, the neutralization test (NT) is the most specific assay available. Different NT protocols are used in the laboratories, and until now the performance of these NTs has never been tested in an external quality assessment (EQA). In this EQA, we compared the results of eight European laboratories in detecting 17 samples (11 TBEV positive, five flavivirus cross reactive, and one negative sample) by NT. Furthermore, 14 of these EQA samples and 15 additional samples were tested in different commercial assays: 15 immunoglobulin G (IgG) enzyme-linked immunosorbent assays (ELISAs) and an immunofluorescence assay (IFA). Four laboratories showed a good NT EQA performance, whereas four laboratories had some sensitivity problems. Additionally, two of these laboratories showed a lack in specificity, misidentifying a dengue-positive sample as TBEV positive. The comparison of the commercial ELISAs revealed a high sensitivity in all assays, but as expected for IgG, the ELISAs showed a high degree of flavivirus cross reactivity. The assessment of Vienna Units in some of the ELISAs revealed deviations in the standards used by the different companies. Therefore, these standards should be revised. Generally, in this EQA, we found that reliable NT protocols are used in most of the laboratories, and the evaluation of the IgG ELISAs and the IFA showed a good agreement.
