Patient description: A previously healthy 8-year-old boy presents with a complaint of right lower extremity pain and fever. He reports limping for the past two days. The parents report no previous trauma, but do remember a tick bite during a summer visit to Maryland several months ago. They do not remember observing erythema migrans. On examination, the right knee is tender and swollen. Peripheral WBC count and SRP are slightly elevated.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Tick-Borne Encephalitis Encephalitis, Tick-Borne Tick-Borne Disease Glycoprotein E, Flavivirus NSI Protein, Flavivirus All subjects must meet the following at study entry Be engaged in activities that place them at potential risk of occupational exposure to TBEV in its viable form at one of the participating intramural laboratories of NIAID Be 18 years of age or older at the time of the first immunization Comprehend the study requirements Provide written informed consent to participate in this study Be in good health as determined by the Investigator, based upon medical history and a targeted physical examination Have a stable health status as determined by the Investigator Have access to a consistent means of telephone contact, which may be either in the home or at the workplace, land line or mobile, but NOT a pay phone or other multiple-user device (i.e., a common use phone serving multiple rooms or apartments) Express availability for the required study period, and ability to attend scheduled visits  The following should be checked at the time of the study entry. If any apply, the subject will not be included in the study The subject must not be participating in any other trial of an investigational drug or vaccine for 1 month prior to the first injection through until 21 days after the third injection. (Given the nature of the work these study subjects engage in, exemptions to this proscription may be granted on a case by case basis after discussion between the Investigator and the IRB.) The presence on the day of immunization of an oral temperature of > 101.2 degrees F or acute symptoms other than mild severity Active systemic infectious process as determined by review of systems and physical examination. The subject may be enrolled at a later date once the illness has resolved Known immune suppression, such as that associated with human immunodeficiency virus infection, or other condition, to the extent that, in the opinion of the Investigator, the subject is likely to have a poor response to the vaccine. This information will be obtained by history only. Serologic screening for these diseases will not be performed Presence of evidence of substance abuse or of neurological or psychiatric diagnoses which, even if clinically stable, are deemed by the Investigator to render the potential subject unable/unlikely to report promptly any adverse reactions to the vaccine Current diagnosis of leukemia, Hodgkin s disease, non-Hodgkin s lymphoma, or any other cancer, autoimmune disease such as lupus, which is in and of itself a cause of immunosuppression to the point that, in the opinion of the Investigator, the subject is likely to have a poor response to the vaccine Currently receiving systemic immunosuppressive chemotherapy or immunotherapy (including glucocorticoids) resulting in immune suppression to the point that, in the opinion of the Investigator, the subject is likely to have a poor response to the vaccine Any neurological condition in which (in the opinion of the Investigator) the integrity of the blood brain barrier may have been compromised Licensed vaccines are not exclusionary but should be given at least 14 days before or after immunization (applies to each of the 3 scheduled TBEV injections) for inactivated vaccines and 30 days before or after immunization with any live vaccines. This is in order to avoid potential confusion of adverse reactions. (Given the nature of the work these study subjects engage in, exemptions to this proscription may be granted on a case-by-case basis after discussion between the Investigator and the IRB.)