Tick-borne Encephalitis Vaccination Research Articles

What makes patients tick? Vaccine preferences against tick-borne encephalitis in four European countries

BackgroundWe explored vaccine motivation and preferences for tick-borne encephalitis (TBE) vaccine attributes among participants in TBE-endemic countries in Europe.MethodsAn online survey was conducted among the general public in Austria, Germany, Switzerland, and Sweden. Participants were ≥ 18 years old, open to receiving vaccines, and living in, or regularly traveling to, TBE-endemic regions in the aforementioned countries. Participants were asked about their general vaccine knowledge and motivations for vaccination, before rating the importance of TBE vaccine attributes, such as efficacy, safety, dosing schedule, and booster interval. Thereafter, participants were shown three hypothetical TBE vaccine profiles with different combinations of attributes. Assuming equal efficacy and safety, participants were asked to select their preferred profile from 12 screens as part of a discrete-choice conjoint analysis. Utility scores were calculated to show the importance of each attribute. Data are presented for the overall survey group and by age and gender, using t-tests to compare means.ResultsFor 73% of participants (n = 1003/1379), self-protection was among the top three reasons to get vaccinated. Disease severity, protection of children or family, and advice or recommendation from a doctor/healthcare professional (HCP) were top three reasons for over half of participants. The majority (58–69%) agreed or strongly agreed that they trust their doctor/HCP on the subject of vaccines, they rely on their doctor/HCP’s vaccine knowledge, and they prefer their doctor/HCP to make recommendations on which vaccines they or their families should take. Efficacy and safety were the most important standalone TBE vaccine attributes; however, among TBE vaccine profiles including 3-, 5- and 10-year booster intervals, the 10-year booster interval was the most influential attribute level when choosing a preferred vaccine profile (utility score: 0.58 [standard error: 0.01]). Differences in motivators and preferences were observed between age and gender subgroups.ConclusionThe high level of doctor/HCP reliance highlights the key role doctors/HCPs play in influencing vaccine decision-making. Booster interval was the biggest driver of choice when selecting a hypothetical TBE vaccine profile, with the strongest preference for a 10-year booster interval. These findings could be used to inform TBE vaccination recommendations and in the further development of TBE vaccines.

Tick-borne Encephalitis Clinical Characteristics in Adult Patients: A 10-year Retrospective Study in Stockholm, Sweden.

The incidence of Tick-borne encephalitis (TBE) has increased during the last decades in Europe. Our aim was to assess the clinical characteristics and outcome of TBE patients in Region Stockholm, as a high-risk area in Sweden. The notification database at the regional Department of Communicable Disease Control and Prevention was used to identify TBE cases during 2006-2015. Clinical data was retrieved from the included patients' medical records. The associations of specific variables to predefined outcomes of disease severity were evaluated with multivariate logistic regression models. Of 1004 identified TBE cases, 703 adult patients were included. Sixty-one percent were men, and the median age was 50 years (range 18-94). The majority were non-vaccinated. Comorbidity was present in 34%, and 4% had immunomodulatory therapy. Seventy-five percent were hospitalised, and 11% had severe disease. More than 70% of the 79 patients followed up for more than 6 months had persisting symptoms. The case fatality rate was 1.4%, with 15% in the group with immunomodulatory treatment. In the multivariate analysis, severe disease was associated with underlying comorbidities, age ≥50 years, and previous complete TBE vaccination. This is the largest cohort of TBE patients in Scandinavia. Our findings of a more severe course of disease in patients of older age, with immunomodulatory therapy, with comorbidities, and vaccination breakthrough infections must be interpreted in the context of hospitalised patients. Optimised prevention is needed for patients with immunomodulatory therapy, given the considerable case fatality rate. Follow-up visits and rehabilitation should be better standardised.

The importance of the role of T-cell immunity in the development of modern tick-borne encephalitis vaccines

The tick-borne encephalitis (TBE) virus is highly pathogenic and can affect the central nervous system, leading to severe chronic effects or death. The only effective measure to combat TBE is vaccine prophylaxis. Vaccines that are currently used for mass immunization are based on inactivated TBE virus, they provide a protective immune response, but such vaccines require multiple administrations. A possible reason for short-term immunity is an incomplete functional T-cell response to these types of vaccines. The aim of this review is to analyze the literature on the role of the T-cell immune response in protecting the body from tick-borne encephalitis, its importance for vaccine development, and to consider approaches to the development of new TBE vaccines based on different platforms. When preparing the review, we analyzed the literature presented in scientific databases — PubMed, Scopus, Elsevier, Google Scholar as of April 2024. The following keywords were used for the search: vaccine, tick-borne encephalitis virus, T-cell immune response, flaviviruses. A several publications have demonstrated that T-cell responses following natural infection with TBE virus and after vaccination with inactivated virus are different. During viral infection, both Th1- and Th2-type CD4+ T cells and CD8+ T cells are activated and play an important role in the elimination of viral infection. After vaccination, the only Th2-type CD4+ T-cell response predominates, which may be the reason for the short-lived immune response. To date, a number of different types of experimental TBE vaccines are being studied, such as live-attenuated vaccines, viral vector vaccines, subunit vaccines, virus-like particles, DNA and mRNA vaccines, and polyepitope immunogens. In our opinion, the most promising in terms of T-cell response activation are vaccines based on T-cell polyepitope immunogens delivered in the form of DNA or mRNA.

Attitudes towards the Tick-Borne Encephalitis Vaccine among Children's Guardians: A Cross-Sectional Survey Study in Poland.

This cross-sectional survey study aimed to assess the attitudes and knowledge of children's guardians in Poland towards tick-borne encephalitis (TBE) and its vaccine, as well as to compare these attitudes to those regarding other infectious diseases and their vaccines. Data were collected through anonymous questionnaires, both paper-based and online, from 3030 respondents across Poland, with the majority being from TBE-endemic areas. The survey included questions on demographic characteristics, general vaccination beliefs, and specific perceptions of TBE and its vaccine. Statistical analysis revealed significant associations between willingness to vaccinate against TBE and factors such as general vaccination attitudes, information sources, vaccine safety ratings, and perceptions of disease severity. Results indicated that guardians from larger cities and those with fewer children were more likely to vaccinate. Additionally, parents who supported general vaccinations were significantly more willing to vaccinate against TBE. The study concludes that enhancing public awareness about the safety and importance of the TBE vaccine, especially in endemic regions, is crucial for improving vaccination rates. Targeted public health interventions addressing misconceptions and providing accurate information are essential strategies to increase TBE vaccine uptake and protect children from this serious disease.

Tick-borne encephalitis vaccine breakthrough infections induce aberrant T cell and antibody responses to non-structural proteins

Tick-borne encephalitis virus (TBEV) vaccine breakthrough (VBT) infections are not uncommon in endemic areas. The clinical and immunological outcomes have been poorly investigated. We assessed the magnitude and specificity of virus-specific antibody and T cell responses after TBE in previously vaccinated subjects and compared the results with those of unvaccinated TBE patients and study subjects that received vaccination without VBT infection. Symptomatic TBEV infection of unvaccinated study subjects induced virus-specific antibody responses to the E protein and non-structural protein 1 (NS1) as well as T cell responses to structural and other non-structural (NS) proteins. After VBT infections, significantly impaired NS1-specific antibody responses were observed, while the virus-specific T cell responses to the NS proteins were relatively strong. VBT infection caused predominantly moderate to severe disease during hospitalization. The level of TBEV EDIII- and NS1-specific antibodies in unvaccinated convalescent patients inversely correlated with TBE severity and neurological symptoms early after infection.

Global Seroprevalence of Tick-Borne Encephalitis Antibodies in Humans, 1956-2022: A Literature Review and Meta-Analysis.

Despite the availability of tick-borne encephalitis (TBE) vaccines, the incidence of TBE is increasing. To understand the historical patterns of infection, we conducted a global meta-analysis of studies before December 2023 reporting human antibody prevalence against TBEV (TBE virus) among general or high-risk population groups stratified by country, collection year, serological method, and vaccination status. Pooled data were compared within groups over time by random-effects modeling. In total, 2403 articles were retrieved; 130 articles published since 1959 were included. Data were extracted from 96 general populations (117,620 participants) and 71 high-risk populations (53,986 participants) across 33 countries. Germany had the most population groups (21), and Poland had the most participants (44,688). Seven serological methods were used; conventional IgG/IgM ELISAs were the most common (44%). Four studies (1.7%) used NS1-ELISA serology. Between 1956-1991 and 1992-2022, anti-TBEV seroprevalence remained at ~2.75% across all population groups from "high-risk" areas (p = 0.458) but decreased within general populations (1.7% to 1%; p = 0.001) and high-risk populations (5.1% to 1.3%; p < 0.001), possibly due to differences in the study methodologies between periods. This global summary explores how serological methods can be used to assess TBE vaccination coverage and potential exposure to TBEV or measure TBE burden and highlights the need for standardized methodology when conducting TBE seroprevalence studies to compare across populations.

Effectiveness of Vaccination Against Tick-Borne Encephalitis in the Czech Republic, 2018-2022.

Background: Tick-borne encephalitis (TBE) is caused by the tick-borne encephalitis virus (TBEV). TBEV infection can cause symptoms of central nervous system (CNS) inflammation and result in severe consequences including death. TBE is an increasing health threat in the Czech Republic and elsewhere in Europe. In 2020, 23% of 3734 TBE cases reported to the European Centre for Disease Prevention and Control were from the Czech Republic. TBE vaccination is universally recommended in the Czech Republic, but a full analysis of TBE vaccine effectiveness (VE) in the Czech Republic has not been published. Methods: TBE is a notifiable disease in the Czech Republic with mandatory reporting of cases (i.e., laboratory-confirmed TBEV infected patient with symptoms of CNS inflammation) and vaccination history to public health authorities. TBE VE was estimated using the screening method utilizing public health surveillance data from 2018 to 2022 and online household surveys of the general population on TBE vaccine uptake conducted in 2019-2022. Results: In 2018-2022, 3648 TBE cases were reported in the Czech Republic; 98.1% (3105/3166) of TBE cases with known vaccination history were unvaccinated. Among 42,671 persons surveyed from the general population who had known TBE vaccination history, 66.5% were unvaccinated. VE against TBE was 97.6% (95% confidence interval 95.7-98.7). When stratified by age group, VE was 97.1% (88.4-99.3) in 1-15 years of age, 97.9% (95.3-99.0) in 16-59 years of age, and 96.9% (90.5-99.0) in ≥60 years of age. TBE vaccination averted an estimated 1020 TBE cases in the Czech Republic from 2018 to 2022. Conclusions: This first published study with a full analysis of TBE VE in the Czech Republic showed that vaccination was highly effective for the prevention of TBE including in children, an age group with increasing TBE disease burden. Vaccination averted hundreds of TBE cases and hospitalizations despite the relatively low compliance with TBE vaccine recommendations. To prevent additional TBE cases in the Czech Republic, enhanced efforts to increase TBE vaccine uptake are needed.

Promoting International Scientific Cooperation: the Role of Scientific Societies

Abstract Scientific collaboration yields many advantages, especially in fields that require interdisciplinary approaches, as it fosters the sharing of knowledge and resources and is essential for the implementation of complex projects. The concept of scientific internationalism emerged around the 1900s, emphasizing that science surpasses national boundaries and promotes global peace and collaboration. International scientific cooperation is halted by geopolitical tensions and conflicts, such as World War II and the Cold War. Nevertheless, many examples show that scientific collaboration can surpass conflicts and bring scientific and society development, such as in the cases of the Tick-borne Encephalitis vaccine, the Apollo-Soyuz test project and more recently the international endeavour for COVID-19 vaccine development. In this contest, UN and WHO have an imporant role to promote peace and scientific cooperation, examplified by the 16th Sustainable Development Goal, to “Promote just, peaceful and inclusive societies”. This review aims to assess the available literature regarding international scientific collaboration and the role of scientific societies in promoting scientific cooperation. Scientific societies have proved to be pivotal in bridging cultures and promoting international cooperation. Apart from the historical example of the International Institute for Applied Systems Analysis, which showed an important cooperation between Western and Eastern countries during the Cold War, the scientific society European Biotechnology thematic network Association (EBTNA) has international scientific cooperation as one of its critical goals. Scientific societies such as EBTNA will be pivotal in promoting international scientific cooperation and fostering international activities and scientific research.

A combined cross-sectional analysis and case-control study evaluating tick-borne encephalitis vaccination coverage, disease and vaccine effectiveness in children and adolescents, Switzerland, 2005 to 2022.

BackgroundTick-borne encephalitis (TBE) is a severe, vaccine-preventable viral infection of the central nervous system. Symptoms are generally milder in children and adolescents than in adults, though severe disease does occur. A better understanding of the disease burden and duration of vaccine-mediated protection is important for vaccination recommendations.AimTo estimate TBE vaccination coverage, disease severity and vaccine effectiveness (VE) among individuals aged 0-17 years in Switzerland.MethodsVaccination coverage between 2005 and 2022 was estimated using the Swiss National Vaccination Coverage Survey (SNVCS), a nationwide, repeated cross-sectional study assessing vaccine uptake. Incidence and severity of TBE between 2005 and 2022 were determined using data from the Swiss disease surveillance system and VE was calculated using a case-control analysis, matching TBE cases with SNVCS controls.ResultsOver the study period, vaccination coverage increased substantially, from 4.8% (95% confidence interval (CI): 4.1-5.5%) to 50.1% (95% CI: 48.3-52.0%). Reported clinical symptoms in TBE cases were similar irrespective of age. Neurological involvement was less likely in incompletely (1-2 doses) and completely (≥ 3 doses) vaccinated cases compared with unvaccinated ones. For incomplete vaccination, VE was 66.2% (95% CI: 42.3-80.2), whereas VE for complete vaccination was 90.8% (95% CI: 87.7-96.4). Vaccine effectiveness remained high, 83.9% (95% CI: 69.0-91.7) up to 10 years since last vaccination.ConclusionsEven children younger than 5 years can experience severe TBE. Incomplete and complete vaccination protect against neurological manifestations of the disease. Complete vaccination offers durable protection up to 10 years against TBE.

Identification of New Microfoci and Genetic Characterization of Tick-Borne Encephalitis Virus Isolates from Eastern Germany and Western Poland.

(1) Background: Tick-borne encephalitis (TBE) is the most important tick-borne viral disease in Eurasia, although effective vaccines are available. Caused by the tick-borne encephalitis virus (TBEV, syn. Orthoflavivirus encephalitidis), in Europe, it is transmitted by ticks like Ixodes ricinus and Dermacentor reticulatus. TBEV circulates in natural foci, making it endemic to specific regions, such as southern Germany and northeastern Poland. Our study aimed to identify new TBEV natural foci and genetically characterize strains in ticks in previously nonendemic areas in Eastern Germany and Western Poland. (2) Methods: Ticks were collected from vegetation in areas reported by TBE patients. After identification, ticks were tested for TBEV in pools of a maximum of 10 specimens using real-time RT-PCR. From the positive TBEV samples, E genes were sequenced. (3) Results: Among 8400 ticks from 19 sites, I. ricinus (n = 4784; 56.9%) was predominant, followed by D. reticulatus (n = 3506; 41.7%), Haemaphysalis concinna (n = 108; 1.3%), and I. frontalis (n = 2; <0.1%). TBEV was detected in 19 pools originating in six sites. The phylogenetic analyses revealed that TBEV strains from Germany and Poland clustered with other German strains, as well as those from Finland and Estonia. (4) Conclusions: Although there are still only a few cases are reported from these areas, people spending much time outdoors should consider TBE vaccination.

Structural diversity of tick-borne encephalitis virus particles in the inactivated vaccine based on strain Sofjin

ABSTRACT The main approach to preventing tick-borne encephalitis (TBE) is vaccination. Formaldehyde-inactivated TBE vaccines have a proven record of safety and efficiency but have never been characterized structurally with atomic resolution. We report a cryoelectron microscopy (cryo-EM) structure of the formaldehyde-inactivated TBE virus (TBEV) of Sofjin-Chumakov strain representing the Far-Eastern subtype. A 3.8 Å resolution reconstruction reveals the structural integrity of the envelope E proteins, specifically the E protein ectodomains. The comparative study shows a high structural similarity to the previously published structures of the TBEV European subtype strains Hypr and Kuutsalo-14. A fraction of inactivated virions exhibits asymmetric features including the deformations of the membrane profile. We propose that the heterogeneity is caused by inactivation and perform a local variability analysis on the small parts of the envelope protein shell to reveal membrane curvature features possibly induced by the inactivation. The results of this study will have implications for the design of novel vaccines against diseases caused by flaviviruses.

Defining the "Correlate(s) of Protection" to tick-borne encephalitis vaccination and infection - key points and outstanding questions.

Tick-borne Encephalitis (TBE) is a severe disease of the Central Nervous System (CNS) caused by the tick-borne encephalitis virus (TBEV). The generation of protective immunity after TBEV infection or TBE vaccination relies on the integrated responses of many distinct cell types at distinct physical locations. While long-lasting memory immune responses, in particular, form the basis for the correlates of protection against many diseases, these correlates of protection have not yet been clearly defined for TBE. This review addresses the immune control of TBEV infection and responses to TBE vaccination. Potential correlates of protection and the durability of protection against disease are discussed, along with outstanding questions in the field and possible areas for future research.

Seroprevalence of tick-borne encephalitis virus and vaccination coverage of tick-borne encephalitis, Sweden, 2018 to 2019.

BackgroundIn Sweden, information on seroprevalence of tick-borne encephalitis virus (TBEV) in the population, including vaccination coverage and infection, is scattered. This is largely due to the absence of a national tick-borne encephalitis (TBE) vaccination registry, scarcity of previous serological studies and use of serological methods not distinguishing between antibodies induced by vaccination and infection. Furthermore, the number of notified TBE cases in Sweden has continued to increase in recent years despite increased vaccination.AimThe aim was to estimate the TBEV seroprevalence in Sweden.MethodsIn 2018 and 2019, 2,700 serum samples from blood donors in nine Swedish regions were analysed using a serological method that can distinguish antibodies induced by vaccination from antibodies elicited by infection. The regions were chosen to reflect differences in notified TBE incidence.ResultsThe overall seroprevalence varied from 9.7% (95% confidence interval (CI): 6.6-13.6%) to 64.0% (95% CI: 58.3-69.4%) between regions. The proportion of vaccinated individuals ranged from 8.7% (95% CI: 5.8-12.6) to 57.0% (95% CI: 51.2-62.6) and of infected from 1.0% (95% CI: 0.2-3.0) to 7.0% (95% CI: 4.5-10.7). Thus, more than 160,000 and 1,600,000 individuals could have been infected by TBEV and vaccinated against TBE, respectively. The mean manifestation index was 3.1%.ConclusionA difference was observed between low- and high-incidence TBE regions, on the overall TBEV seroprevalence and when separated into vaccinated and infected individuals. The estimated incidence and manifestation index argue that a large proportion of TBEV infections are not diagnosed.

Inapparent Tick-Borne Orthoflavivirus Infection in Macaca fascicularis: A Model for Antiviral Drug and Vaccine Research.

Tick-borne encephalitis virus (TBEV) and Powassan virus (POWV) are neurotropic tick-borne orthoflaviviruses. They cause mostly asymptomatic infections in hosts, but severe forms with CNS involvement can occur. Studying the early stages of viral infections in humans is challenging, and appropriate animal models are essential for understanding the factors determining the disease severity and for developing emergency prophylaxis and treatment options. In this work, we assessed the model of the early stages of TBEV and POWV mono- and co-infections in Macaca fascicularis. Serological, biochemical, and virological parameters were investigated to describe the infection, including its impact on animal behavior. Viremia, neutralizing antibody dynamics, and viral load in organs were chosen as the main parameters distinguishing early-stage orthoflavivirus infection. Levels of IFNα, monocyte count, and cognitive test scores were proposed as additional informative indicators. An assessment of a tick-borne encephalitis vaccine using this model showed that it provided partial protection against POWV infection in Macaca fascicularis without signs of antibody-dependent enhancement of infection.

Tick-Borne Encephalitis Vaccine: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023.

Ixodes species ticks but can also be acquired less frequently by alimentary transmission. Other rare modes of transmission include through breastfeeding, blood transfusion, solid organ transplantation, and slaughtering of viremic animals. TBE virus can cause acute neurologic disease, which usually results in hospitalization, often permanent neurologic or cognitive sequelae, and sometimes death. TBE virus infection is a risk for certain travelers and for laboratory workers who work with the virus. In August 2021, the Food and Drug Administration approved Ticovac TBE vaccine for use among persons aged ≥1 year. This report summarizes the epidemiology of and risks for infection with TBE virus, provides information on the immunogenicity and safety of TBE vaccine, and summarizes the recommendations of the Advisory Committee on Immunization Practices (ACIP) for use of TBE vaccine among U.S. travelers and laboratory workers.

Tick-Borne Encephalitis Virus Vaccination among Tourists in a High-Prevalence Area (Italy, 2023): A Cross-Sectional Study.

Tick-borne encephalitis (TBE) represents a potential health threat for tourists in high-risk areas, including the Dolomite Mountains in northeastern Italy. The present questionnaire-based survey was, therefore, designed in order to assess knowledge, attitudes, and preventive practices (KAP) in a convenience sample of Italian tourists visiting the Dolomite Mountains, who were recruited through online discussion groups. A total of 942 participants (39.2% males, with 60.2% aged under 50) filled in the anonymous survey from 28 March 2023 to 20 June 2023. Overall, 24.1% of participants were vaccinated against TBE; 13.8% claimed to have previously had tick bites, but no cases of TBE were reported. The general understanding of TBE was relatively low; while 79.9% of participants acknowledged TBE as a potentially severe disease, its occurrence was acknowledged as high/rather high or very high in the Dolomites area by only 51.6% of respondents. Factors associated with the TBE vaccine were assessed by the calculation of adjusted odds ratios (aOR) and 95% confidence intervals through a logistic regression analysis model. Living in areas considered at high risk for TBE (aOR 3.010, 95%CI 2.062-4.394), better knowledge on tick-borne disorders (aOR 1.515, 95%CI 1.071-2.142), high risk perception regarding tick-borne infections (aOR 2.566, 95%CI 1.806-3.646), a favorable attitude toward vaccinations (aOR 3.824, 95%CI 1.774-8.224), and a tick bite(s) in a previous season (aOR 5.479, 95%CI 3.582-8.382) were characterized as being positively associated with TBE vaccination uptake. Conversely, being <50 years old (aOR 0.646, 95%CI, 0.458-0.913) and with a higher risk perception regarding the TBE vaccine (aOR 0.541, 95%CI 0.379-0.772) were identified as the main barriers to vaccination. In summary, tourists to the high-risk area of the Dolomites largely underestimate the potential occurrence of TBE. Even though the uptake of the TBE vaccine in this research was in line with European data, public health communication on TBE is required in order to improve acceptance of this effective preventive option.

Effect of previous heterologous flavivirus vaccinations on human antibody responses in tick-borne encephalitis and dengue virus infections.

Arthropod-borne flaviviruses include a number of medically relevant human pathogens such as the mosquito-borne dengue (DEN), Zika, and yellow fever (YF) viruses as well as tick-borne encephalitis virus (TBEV). All flaviviruses are antigenically related and anamnestic responses due to prior immunity can modulate antibody specificities in subsequent infections or vaccinations. In our study, we analyzed the induction of broadly flavivirus cross-reactive antibodies in tick-borne encephalitis (TBE) and DEN patients without or with prior flavivirus exposure through TBE and/or YF vaccination, and determined the contribution of these antibodies to TBE and dengue virus (DENV) neutralization. In addition, we investigated the formation of cross-reactive antibodies in TBE-vaccination breakthroughs (VBTs). A TBEV infection without prior YF or TBE vaccination induced predominantly type-specific antibodies. In contrast, high levels of broadly cross-reactive antibodies were found in samples from TBE patients prevaccinated against YF as well as in DEN patients prevaccinated against TBE and/or YF. While these cross-reactive antibodies did not neutralize TBEV, they were effective in neutralizing DENV. This discrepancy points to structural differences between the two viruses and indicates that broadly cross-reactive epitopes are less accessible in TBEV than in DENV. In TBE VBT infections, type-specific antibodies dominated the antibody response, thus revealing no difference from that of unvaccinated TBE patients. Our results emphasize significant differences in the structural properties of different flaviviruses that have an impact on the induction of broadly cross-reactive antibodies and their functional activities in virus neutralization.

The long-term efficacy of tick-borne encephalitis vaccines available in Europe - a systematic review

BackgroundDespite the availability of vaccination, TBE (tick-borne encephalitis) remains a global public health problem. Therefore, the aim of our study was to assess the long-term efficacy of vaccinations against tick-borne encephalitis using vaccines available on the European market.MethodsThe analysis was conducted on the results of a systematic review conducted in accordance with the Cochrane Handbook for Systematic Reviews of Interventions. The search was performed in three databases, namely Medline (via PubMed), EMBASE (via Ovid), and the Cochrane Library database. The authors followed the PRISMA method and the selection of the articles was performed with two independent researchers.ResultsFrom a total of 199 citations, 9 studies were included in this review. According to the primary studies identified in the search, the efficacy of available anti-TBE vaccines ranges from 90.1% to 98.9%; however, in individuals above the age of 60, the protection wanes as early as one year after vaccination. Administration of a booster dose 3 years after completion of the basic vaccination schedule significantly extended the period of protection against TBE.ConclusionsAnti-TBE vaccines available in Europe have a high level of efficacy. However, the level of protection against TBE is decreasing after vaccination. Therefore, in addition to the conventional schedule, booster vaccines should be administered every 5 years in individuals before the age of 60 and more frequently, e.g. every 3 years, in individuals aged 60 and beyond.

Study of a tick-borne encephalitis vaccine

Scientific relevance. Tick-borne encephalitis is one of the most significant anthropozoonoses for public health in the Russian Federation. Wide vaccination coverage is required to control this zoonotic infection. However, large-scale immunisation is not feasible without developing novel vaccines with improved safety and efficacy profiles, such as vaccines based on the continuous Vero cell line.Aim. This extended study aimed to investigate the key quality attributes of VeroKSEN, a new tick-borne encephalitis vaccine that was obtained using Vero cells.Materials and methods. The authors implemented current approaches to vaccine development, including propagation of tick-borne encephalitis strain 205 (Far Eastern subtype) in Vero cells, fine purification of the viral antigen by size-exclusion chromatography on polymeric resins, and introduction of additional quality control methods. For VeroKSEN production, the authors used the method protected by utility patent No. 2678431. Quality control of the finished product was performed according to the State Pharmacopoeia of the Russian Federation. The laboratory study of the vaccine and its intermediates in Balb/с mice used novel control methods developed by the authors. Additional methods included polyacrylamide gel electrophoresis, enzyme immunoassay, immunoblotting with total antibodies to tick-borne encephalitis virus and monoclonal antibodies to glycoprotein E, reverse transcription–polymerase chain reaction, and high-performance liquid chromatography. The extended potency study used test strains of different subtypes, including Absettarov (Western), Sofjin (Far Eastern), and Korzukhin (Siberian). The authors studied the infectious activity of tick-borne encephalitis virus in outbred mice using the pharmacopoeial titration method. Statistical analysis of the study results involved calculating the arithmetic mean and the root-mean-square deviation.Results. The authors studied the key quality attributes of VeroKSEN and its intermediates. Selected inactivation conditions reduced the infectious activity of the viral harvest to an undetectable level within 24 h, while its antigenic activity remained approximately 100% of the baseline. The fine purification stages and the methods and techniques developed by the authors provided a whole-virion fraction with a purity of up to 98.2% and removed process-related impurities (residual host-cell DNA, bovine serum albumin, formaldehyde, and bacterial endotoxins) to the levels required by national legislation. The stability study demonstrated that the vaccine met the requirements for up to 36 months.Conclusions. The study showed the high potency of the new vaccine in terms of protection against the Western, Siberian, and Far Eastern subtypes of tick-borne encephalitis, with minimum immunising doses (MID50) of 0.007, 0.00125, and 0.00093 mL, respectively.

Arbovirology and Cold War Collaborations: A Transnational History of the Tick-borne Encephalitis Vaccine, 1930-1980.

This article analyzes the history of immunization against tick-borne encephalitis (TBE) and specifically the processes that led to the creation and application of TBE vaccines in the Soviet Union and Austria. Rather than presenting the development of TBE vaccines from the perspective of national scientific schools, the article investigates their history as a transnational project, focusing on the connections among the Soviet Union, Czechoslovakia, Austria, the United States, and the United Kingdom. It argues that biomedical research on TBE was profoundly intertwined with political and military agendas and depended on civil international cooperation as well as Soviet, American, and British military concerns, infrastructures and funding. The article consists of four parts that discuss (1) the identification of the TBE virus and the creation of the first TBE vaccine in the Soviet Union in the 1930s; (2) the internationalization of TBE research and vaccine development in the 1940s-1960s; (3) the history of TBE research and virology in Austria in the 1930s-1960s and the role of the US military funding; and (4) the cooperation of Austrian virologist Christian Kunz with the Microbiological Research Establishment Porton Down in the UK leading to the development of the Austrian/British vaccine against TBE in the 1970s.