First evidence of tick-borne encephalitis (TBE) outside of Hokkaido Island in Japan

Status Epilepticus Caused by Tick-borne Encephalitis: A Case Report

We herein report a rare case of a 78-year-old Japanese man who developed refractory status epilepticus due to tick-borne encephalitis (TBE). The patient initially presented with left-sided hemiplegia and loss of consciousness. Initial diagnostic tests could not identify the cause of the encephalomyelitis, leading to a preliminary diagnosis of autoimmune encephalomyelitis. Despite treatment with corticosteroids and plasma exchange, the patient experienced status epilepticus, which required multiple antiseizure medications. TBE viral antibodies were eventually detected, confirming the diagnosis. Despite the treatment, the patient remained critically ill. Clinicians should consider TBE in the differential diagnosis of encephalitis of unknown origin associated with status epilepticus.

Phase 3 immunogenicity and safety study of a tick-borne encephalitis vaccine in healthy Japanese participants 1 year of age and older

BACKGROUND

Tick-borne encephalitis (TBE) virus infects the central nervous system and may lead to severe neurological complications or death. This study assessed immunogenicity, safety, and tolerability of TBE vaccine in Japanese participants 1 year of age and older.

METHODS

This phase 3, multicenter, single-arm, open-label study was conducted in Japanese adult (≥ 16 years) and pediatric (1-< 16 years) populations. Participants received a single 0.5-mL (adult) or 0.25-mL (pediatric) dose of TBE vaccine at each of 3 visits. The primary endpoint was the proportion of participants who were seropositive (neutralization test [NT] titer ≥ 1:10) 4 weeks after Dose 3. Secondary and exploratory endpoints included NT seropositivity rates 4 weeks after Dose 2, immunoglobulin G (IgG) seropositivity 4 weeks after Doses 2 and 3, NT geometric mean titers (GMTs), IgG geometric mean concentrations (GMCs), and geometric mean fold rises. Primary safety endpoints were frequencies of local reactions, systemic events, adverse events (AEs), and serious AEs.

RESULTS

Among 100 adult and 65 pediatric participants, 99.0 % and 100.0 % completed the study, respectively. NT seropositivity was achieved in 98.0 % adult and 100.0 % pediatric participants after Dose 3; seropositivity after Dose 2 was 93.0 % and 92.3 %, respectively. In both age groups, IgG seropositivity was ≥ 90.0 % and ≥ 96.0 % after Doses 2 and 3, respectively; GMTs and GMCs were highest 4 weeks after Dose 3. Reactogenicity events were generally mild to moderate in severity and short-lived. AEs were reported by 15.0 % (adult) and 43.1 % (pediatric) of participants. No life-threatening AEs, AEs leading to discontinuation, immediate AEs, related AEs, or deaths were reported. No serious AEs were considered related to TBE vaccine.

CONCLUSIONS

TBE vaccine elicited robust immune responses in Japanese participants 1 year of age and older. The 3-dose regimen was safe and well tolerated, and findings were consistent with the known safety profile of this TBE vaccine.

CLINICALTRIALS

gov: NCT04648241.

Adult-Onset Encephalitis over Twelve Years in Easternmost Finland

INTRODUCTION

The epidemiology of encephalitis varies by region and time. Available Finnish data are outdated and there are no data from eastern parts of the country nor concerning the occurrence of autoimmune encephalitides.

MATERIALS AND METHODS

Patients with encephalitis were identified from mandatory administrative registries in North Karelia Central Hospital. The diagnoses were verified and data extracted by reviewing the patient records. Study period was 2010-2021. Only patients >16 years of age were included.

RESULTS

Fifty-one patients with a clinical encephalitis were identified (55% men) with a median age of 65 years (interquartile range 45, 73; total age range 16-88 years) indicating a crude incidence of 3.1/100,000 person-years for the entire study period. A specific aetiology could be identified in 31 cases (61%) with tick-borne encephalitis (TBE) being the most common one (20% of all 51 cases), followed by herpes simplex virus type 1 (HSV-1, 16%) and varicella zoster virus (VZV, 14%). Autoimmune aetiology was confirmed in 10%. TBE was most often found in the youngest age group (16-52 years of age) and the herpes viruses in the oldest group (71 years or older). A specific cause was most often identified in the oldest patients (78%). TBE patients were younger than patients with VZV (p = 0.0009) or HSV-1 (p = 0.0057), but there was no difference when they were compared to patients with autoimmune (p = 0.27) or unknown (p = 0.074) aetiology. At presentation, there were differences in the occurrence of some clinical signs and symptoms between aetiologies but nothing specific. Eight patients (16%) were immunosuppressed. Inpatient seizures occurred in 10 patients (20%). In these cases, the aetiology was HSV-1 in 50% and TBE or VZV in none. A full recovery was observed in 51% of all patients while 3 patients (6%) had died of the encephalitis while in hospital or shortly after discharge.

CONCLUSIONS

Adult-onset encephalitis was more common and the patients older in easternmost Finland than previously reported in other parts of the country. TBE, HSV-1, and VZV are the most commonly identified specific aetiologies whereas a fifth of the cases are probably caused by autoimmunity. Prognosis depended on aetiology but was very good in the majority of cases.