Vaccines

Background: Although annual influenza vaccination is an important strategy used to prevent influenza-related morbidity and mortality, some studies have reported the negative influence of prior vaccination on vaccine effectiveness (VE) for current seasons. Currently, the influence of prior vaccination is not conclusive, especially in children. Methods: We evaluated the association between current-season VE and prior season vaccination using a test-negative design in children aged 1–5 years presenting at nine outpatient clinics in Japan during the 2016/17 and 2017/18 influenza seasons. Children with influenza-like illness were enrolled prospectively and tested for influenza using real-time RT-PCR. Their recent vaccination history was categorized into six groups according to current vaccination doses (0/1/2) and prior vaccination status (unvaccinated = 0 doses/vaccinated = 1 dose or 2 doses): (1) 0 doses in the current season and unvaccinated in prior seasons (reference group); (2) 0 doses in the current season and vaccinated in a prior season; (3) 1 dose in the current season and unvaccinated in a prior season; (4) 1 dose in the current season and vaccinated in a prior season; (5) 2 doses in the current season and unvaccinated in a prior season, and (6) 2 doses in the current season and vaccinated in a prior season. Results: A total of 799 cases and 1196 controls were analyzed. The median age of the subjects was 3 years, and the proportion of males was 54%. Overall, the vaccination rates (any vaccination in the current season) in the cases and controls were 36% and 53%, respectively. The VEs of the groups were: (2) 29% (95% confidence interval: −25% to 59%); (3) 53% (6% to 76%); (4) 70% (45% to 83%); (5) 56% (32% to 72%), and (6) 61% (42% to 73%). The one- and two-dose VEs of the current season were significant regardless of prior vaccination status. The results did not differ when stratified by influenza subtype/lineage. Conclusion: Prior vaccination did not attenuate the current-season VE in children aged 1 to 5 years, supporting the annual vaccination strategy. Full article

T cell activation by antigen involves multiple sequential steps, including T cell receptor-microcluster TCR-(MC) formation, immunological synapse formation, and phosphorylation of mediators downstream of the TCR. The adaptor protein, Disc Large Homolog 1 (DLG1), is known to regulate proximal TCR signaling and, in turn, T cell activation, acting as a molecular chaperone that organizes specific kinases downstream of antigen recognition. In this study, we used knockdown and knockout technologies in human primary T cells and a human T cell line to demonstrate the role of DLG1 in proximal T cell signaling. High-end confocal microscopy was used for pictorial representation of T cell micro-clusters and colocalization studies. From all these studies, we could demonstrate that DLG1 functions even earlier than immunological synapse formation, to regulate T cell activation by promoting TCR-MC formation. Moreover, we found that DLG1 can act as a bridge between the TCR-ζ chain and ZAP70 while inhibiting binding of the phosphatase SHP1 to TCR-ζ. Together, these effects drive dysregulation of T cell activation in DLG1-deficient T cells. Overall, the activation and survival status of T cell is a critical determinant of effective vaccine response, and DLG1-mediated T cell signaling events can be a driving factor for improving vaccine-designing strategies. Full article

Vaccine hesitancy is one of the top ten greatest threats to global health. During the COVID-19 era, vaccine hesitancy poses substantial risks, especially in visible minorities, who are disproportionately affected by the pandemic. Although evidence of vaccine hesitancy exists, there is minimal focus on visible minorities and the reasons for hesitancy in this group are unclear. Identifying these populations and their reasons for vaccine hesitancy is crucial in improving vaccine uptake and curbing the spread of COVID-19. This scoping review follows a modified version of the Arksey and O’Malley strategy. Using comprehensive search strategies, advanced searches were conducted on Medline, CINAHL, and PubMed databases to acquire relevant articles. Full-text reviews using inclusion and exclusion criteria were performed to extract themes of vaccine hesitancy. Themes were grouped into factors using thematic qualitative analysis and were objectively confirmed by principal component analysis (PCA). To complement both analyses, a word cloud of titles and abstracts for the final articles was generated. This study included 71 articles. Themes were grouped into 8 factors and the top 3 recurring factors were safety and effectiveness of the vaccine, mistrust, and socioeconomic characteristics. Shedding light on these factors could help mitigate health inequities and increase overall vaccine uptake worldwide through interventions and policies targeted at these factors. Ultimately, this would help achieve global herd immunity. Full article

The pandemic state has a destructive effect on the human psyche and induces fear for one’s own health. By reducing the risk of severe COVID-19, vaccination may indirectly improve the mental state. This study aims to assess the effects of vaccination on respondents’ mental well-being, their attitudes towards adherence to government recommendations limiting viral transmission, and to identify factors that may influence the decision to get vaccinated. The survey took the form of the authors’ own, fully voluntary, anonymous, online questionnaire. Standardised psychometric tools were used in the survey: Generalised Anxiety Disorder Assessment (GAD-7) and Manchester Short Assessment of Quality of Life (MANSA). The survey involved 1696 respondents, the vast majority of whom were women, and were aged 18–29. The vaccination status was declared by 1677 respondents (98.9%), 430 (25.4%) of whom were vaccinated with at least one dose of vaccine, while 303 (17.9%) respondents were not only unvaccinated at all, and declared no intention to get vaccinated in the future. Fully vaccinated individuals were found to have lower levels of anxiety, higher MANSA scores and lower subjective anxiety about being infected with COVID-19 than those awaiting vaccination or those with an incomplete vaccination regimen (one dose). Those who are not willing to get vaccinated have the lowest sense of anxiety and fear of being infected and they have the lowest adherence to government recommendations limiting SARS-CoV-2 transmission. Conclusions: COVID-19 vaccination reduces the level of anxiety about being infected and anxiety due to COVID-19 disease in people from the immediate environment. Those who are not willing to get vaccinated have extreme attitudes that negate the pandemic as a whole, including the need for COVID-19 vaccination. Fully vaccinated individuals still adhere to the SARS-CoV-2 prevention policies in place. Full article

Infectious bursal disease (IBD), caused by the infectious bursal disease virus (IBDV), is a highly contagious and immunosuppressive disease in chickens worldwide. The novel variant IBDV (nvIBDV) has been emerging in Chinese chicken farms since 2017, but there are no available vaccines that can provide effective protection. Herein, the capsid protein VP2 from nvIBDV strain FJ-18 was expressed in Kluyveromyces marxianus with the aim to produce nvIBDV subviral particles (SVPs). Two recombinant strains constructed for expression of nvIBDV VP2 (nvVP2) and His-tagged VP2 (nvHVP2) formed two types of nvIBDV subviral particles (SVPs), namely nvVP2-SVPs and nvHVP2-SVPs. TEM scans showed that both SVPs were about 25 nm in diameter, but there was a large portion of nvVP2-SVPs showing non-spherical particles. Molecular dynamics simulations indicate that an N-terminal His tag strengthened the interaction of the nvHVP2 monomer and contributed to the assembly of SVPs. Vaccination of chicks with the nvHVP2-SVPs provided 100% protection against novel variant IBDV infection when challenged with the FJ-18 strain, as well as the classical strain BC6/85. By contrast, vaccination with the nvVP2-SVPs only provided 60% protection against their parent FJ-18 strain, suggesting that the stable conformation of subviral particles posed a great impact on their protective efficacy. Our results showed that the nvHVP2-SVPs produced by the recombinant K. marxianus strain is an ideal vaccine candidate for IBDV eradication. Full article

Vaccinating recovered patients previously infected by COVID-19 with mRNA vaccines to boost their immune response against wild-type viruses (WT), we aimed to investigate whether vaccine platform and time of vaccination affect immunogenicity against the SARS-CoV-2 WT and Delta variant (DV). Convalescent patients infected by COVID-19 were recruited and received one booster dose of the BNT162b2 (PC-B) or CoronaVac (PC-C) vaccines, while SARS-CoV-2 naïve subjects received two doses of the BNT162b2 (CN-B) or CoronaVac (CN-C) vaccines. The neutralizing antibody in sera against the WT and DV was determined with live virus neutralization assay (vMN). The vMN geometric mean titre (GMT) against WT in recovered individuals previously infected by COVID-19 reduced significantly from 60.0 (95% confidence interval (CI), 46.5–77.4) to 33.9 (95% CI, 26.3–43.7) at 6 months post recovery. In the PC-B group, the BNT162b2 vaccine enhanced antibody response against WT and DV, with 22.3-fold and 20.4-fold increases, respectively. The PC-C group also showed 1.8-fold and 2.2-fold increases for WT and DV, respectively, after receiving the CoronaVac vaccine. There was a 10.6-fold increase in GMT in the CN-B group and a 1.3-fold increase in the CN-C group against DV after full vaccination. In both the PC-B and PC-C groups, there was no difference between GMT against WT and DV after vaccination. Subjects in the CN-B and CN-C groups showed inferior GMT against DV compared with GMT against WT after vaccination. In this study, one booster shot effectively enhanced the pre-existing neutralizing activity against WT and DV in recovered subjects. Full article

Viral nervous necrosis (VNN) caused by the nervous necrosis virus (NNV) affects a broad range of primarily marine fish species, with mass mortality rates often seen among larvae and juveniles. Its genetic diversification may hinder the effective implementation of preventive measures such as vaccines. The present study describes different inactivation procedures for developing an inactivated vaccine against a new NNV isolate confirmed to possess deadly effects upon the European seabass (Dicentrarchus labrax), an important Mediterranean farmed fish species that is highly susceptible to this disease. First, an NNV isolate from seabass adults diagnosed with VNN was rescued and the sequences of its two genome segments (RNA1 and RNA2) were classified into the red-spotted grouper NNV (RGNNV) genotype, closely clustering to the highly pathogenic 283.2009 isolate. The testing of different inactivation procedures revealed that the virus particles of this isolate showed a marked resistance to heat (for at least 60 °C for 120 min with and without 1% BSA) but that they were fully inactivated by 3 mJ/cm² UV-C irradiation and 24 h 0.2% formalin treatment, which stood out as promising NNV-inactivation procedures for potential vaccine candidates. Therefore, these procedures are feasible, effective, and rapid response strategies for VNN control in aquaculture. Full article

Glycoprotein E (gE) is one of the most abundant glycoproteins in varicella-zoster virus and plays pivotal roles in virus replication and transmission between ganglia cells. Its extracellular domain has been successfully used as an antigen in subunit zoster vaccines. The intracellular C-terminal domain was reported to be decisive for gE trafficking between the endoplasmic reticulum, trans-Golgi network and endosomes and could influence virus spread and virus titers. Considering that the trafficking and distribution of mRNA vaccine-translated gE may be different from those of gE translated against the background of the viral genome (e.g., most gE in virus-infected cells exists as heterodimers with another glycoprotein, gI,), which may influence the immunogenicity of gE-based mRNA vaccines, we compared the humoral and cellular immunity induced by LNP-encapsulated mRNA sequences encoding the whole length of gE, the extracellular domain of gE and a C-terminal double mutant of gE (mutant Y569A with original motif AYRV, which targets gE to TGN, and mutants S593A, S595A, T596A and T598A with the original motif SSTT) that were reported to enhance virus spread and elevate virus titers. The results showed that while the humoral and cellular immunity induced by all of the mRNA vaccines was comparable to or better than that induced by the AS01B-adjuvanted subunit vaccines, the C-terminal double mutant of gE showed stable advantages in all of the indicators tested, including gE-specific IgG titers and T cell responses, and could be adopted as a candidate for both safer varicella vaccines and effective zoster vaccines. Full article

Memory T-cell responses following infection with coronaviruses are reportedly long-lived and provide long-term protection against severe disease. Whether vaccination induces similar long-lived responses is not yet clear since, to date, there are limited data comparing memory CD4+ T-cell responses induced after SARS-CoV-2 infection versus following vaccination with BioNTech/Pfizer BNT162b2. We compared T-cell immune responses over time after infection or vaccination using ELISpot, and memory CD4+ T-cell responses three months after infection/vaccination using activation-induced marker flow cytometric assays. Levels of cytokine-producing T-cells were remarkably stable between three and twelve months after infection, and were comparable to IFNγ+ and IFNγ+IL-2+ T-cell responses but lower than IL-2+ T-cell responses at three months after vaccination. Consistent with this finding, vaccination and infection elicited comparable levels of SARS-CoV-2 specific CD4+ T-cells after three months in addition to comparable proportions of specific central memory CD4+ T-cells. By contrast, the proportions of specific effector memory CD4+ T-cells were significantly lower, whereas specific effector CD4+ T-cells were higher after infection than after vaccination. Our results suggest that T-cell responses—as measured by cytokine expression—and the frequencies of SARS-CoV-2-specific central memory CD4+T-cells—indicative of the formation of the long-lived memory T-cell compartment—are comparably induced after infection and vaccination. Full article

In organ transplant recipients, the rate of invasive pneumococcal diseases is 25 times greater than in the general population. Vaccination against S. pneumoniae is recommended in this cohort because it reduces the incidence of this severe form of pneumococcal infection. Previous studies indicate that transplant recipients can produce specific antibodies after pneumococcal vaccination. However, it remains unclear if vaccination also induces specific cellular immunity. In the current study on 38 kidney transplant recipients, we established an interferon-γ ELISpot assay that can detect serotype-specific cellular responses against S. pneumoniae. The results indicate that sequential vaccination with the conjugated vaccine Prevenar 13 and the polysaccharide vaccine Pneumovax 23 led to an increase of serotype-specific cellular immunity. We observed the strongest responses against the serotypes 9N and 14, which are both components of Pneumovax 23. Cellular responses against S. pneumoniae correlated positively with specific IgG antibodies (r = 0.32, p = 0.12). In conclusion, this is the first report indicating that kidney transplant recipients can mount specific cellular responses after pneumococcal vaccination. The ELISpot we established will allow for further investigations. These could help to define, for example, factors influencing specific cellular immunity in immunocompromised cohorts or the duration of cellular immunity after vaccination. Full article

The emerging SARS-CoV-2 variants and waning vaccine-elicited immunity are two public health challenges that occurred simultaneously and synergistically during the summer of 2021 and led to a surging demand for COVID-19 vaccine booster dose (BD) rollout. This study aimed to evaluate the COVID-19 vaccine booster hesitancy (VBH) among Czech healthcare workers to explore the potential determinants of VBH. A national cross-sectional survey-based study was carried out between 3 and 11 November 2021, using an online self-administered questionnaire (SAQ) that explored the participants’ demographic characteristics, COVID-19 infection and vaccine anamneses, willingness to receive COVID-19 vaccine BD, and the psychosocial drivers of VBH. A total of 3454 HCW properly responded to the online SAQ, of which 80.9% were females, 30.3% were medical professionals, and 50.5% were ≤47 years old. Most of the participants were already inoculated against SARS-CoV-2 (95.2%), and BTN162b2 was the most commonly administered vaccine (90.7%). As the study sample was planned to represent the target population, it revealed a high level of BD acceptance (71.3%) among Czech HCW, while 12.2% were still hesitant and 16.6% were against the currently available BD. These results are consistent with other recent results from central Europe. Medical professional, male, and older participants were more likely to accept BD rather than allied health professional, female, and younger participants. The BDs’ perceived effectiveness against severe illness, symptomatic infection, and community transmission was a significant and strong predictor for BD acceptance, while the effectiveness against the circulating variants was not that important for our target population. The BDs’ perceived safety and ethical dilemmas of vaccine justice should be addressed sufficiently while communicating with HCW and other population groups. The altruistic reasons for BD acceptance, i.e., family protection, patient protection, and community health protection, underpin the recommendation of postponing the COVID-19 vaccine mandating in favour of stressing these altruistic concerns amid public health messaging. Full article

Rabies is an ancient disease that is responsible for approximately 59,000 human deaths annually. Bats (Order Chiroptera) are thought to be the original hosts of rabies virus (RABV) and currently account for most rabies cases in wildlife in the Americas. Vaccination is being used to manage rabies in other wildlife reservoirs like fox and raccoon, but no rabies vaccine is available for bats. We previously developed a recombinant raccoonpox virus (RCN) vaccine candidate expressing a mosaic glycoprotein (MoG) gene that protected mice and big brown bats when challenged with RABV. In this study, we developed two new recombinant RCN candidates expressing MoG (RCN-tPA-MoG and RCN-SS-TD-MoG) with the aim of improving RCN-MoG. We assessed and compared in vitro expression, in vivo immunogenicity, and protective efficacy in vaccinated mice challenged intracerebrally with RABV. All three candidates induced significant humoral immune responses, and inoculation with RCN-tPA-MoG or RCN-MoG significantly increased survival after RABV challenge. These results demonstrate the importance of considering molecular elements in the design of vaccines, and that vaccination with either RCN-tPA-MoG or RCN-MoG confers adequate protection from rabies infection, and either may be a sufficient vaccine candidate for bats in future work. Full article

Age is among the most prominent risk factors for developing severe COVID-19 disease, and therefore older adults are a major target group for vaccination against SARS-CoV-2. This review focusses on age-associated aspects of COVID-19 vaccines and vaccination strategies, and summarizes data on immunogenicity, efficacy and effectiveness of the four COVID-19 vaccines, which are licensed in the US and/or Europe; namely, the two mRNA vaccines by BioNTech/Pfizer (BNT162b2) and Moderna (mRNA-1273), and the adenovector vaccines developed by AstraZeneca/University Oxford (ChAdOx1-nCoV-19, AZD1222) and Janssen/Johnson&Johnson (Ad26.COV2-S), respectively. After very high protection rates in the first months after vaccination even in the older population, effectiveness of the vaccines, particularly against asymptomatic infection and mild disease, declined at later time points and with the emergence of virus variants. Many high-income countries have recently started administration of additional doses to older adults and other high-risk groups, whereas other parts of the world are still struggling to acquire and distribute vaccines for primary vaccination. Other vaccines are available in other countries and clinical development for more vaccine candidates is ongoing, but a complete overview of COVID-19 vaccine development is beyond the scope of this article. Full article

Ensuring timely access to affordable vaccines has been acknowledged as a global public health priority, as also recently testified by the debate sparked during the COVID-19 pandemic. Effective vaccine procurement strategies are essential to reach this goal. Nevertheless, this is still a neglected research topic. A narrative literature review on vaccine procurement was conducted, by retrieving articles from four academic databases (PubMed/MEDLINE, Scopus, Embase, WebOfScience), ‘grey’ literature reports, and institutional websites. The aim was to clarify key concepts and definitions relating to vaccine procurement, describe main vaccine procurement methods, and identify knowledge gaps and future perspectives. A theoretical conceptual framework was developed of the key factors involved in vaccine procurement, which include quality and safety of the product, forecasting and budgeting, procurement legislation, financial sustainability, and plurality of manufacture, contracting, investment in training, storage and service delivery, monitoring and evaluation. This information can be useful to support policymakers during planning, implementation, and evaluation of regional and national vaccine procurement strategies and policies. Full article

Recommendations by health professionals are important for vaccines that are not included in national schedules. This study explored health professionals’ perspectives on recommending non-scheduled (user-fee) childhood vaccinations in China, identifying key influences on professionals’ interactions with caregivers. We conducted individual semi-structured interviews with 20 health professionals from three provinces in China and analyzed data thematically using deductive and inductive coding. Health professionals from all three provinces were uncomfortable about being perceived to encourage parents to accept vaccines that incurred a fee. They provided information about non-scheduled vaccines but emphasized parental autonomy in decision-making. Rural parents were less aware of unscheduled vaccines and health professionals were more likely to encourage parents living in more affluent areas to consider these vaccines; varicella vaccine was preferred by parents as a way of preventing school absence. Economic incentives for unscheduled vaccines were given to staff at most study sites, although the amount given varied widely. These variations meant that staff receiving lower incentives were not motivated to promote non-scheduled vaccines if their workload was high; on the contrary, those receiving higher incentives were more likely to promote these vaccines. Health professionals need more guidance on how to recommend unscheduled vaccines in an informative, positive and appropriate manner. It is evident that parents’ awareness of these vaccines, and their economic circumstances, influence vaccinators recommendation practice. Economic incentives prompted health professionals to recommend non-scheduled vaccines; however, the application of such staff incentives varied widely in China. To adopt appropriate economic incentives, professional organizations should develop protocols for the use of incentives that account for their influence on recommendation practices. Suitable recommendation policy needs to balance basic salaries with performance-based incentives, consider overall workload, and include monitoring and evaluation of economic incentives. Full article

Cervical cancer is a leading cause of morbidity and mortality in women worldwide. The availability of prophylactic vaccines for high-risk types of human papillomavirus (HPV) infection represents an important advancement in the prevention of cervical cancer. In Jordan, the availability of the HPV vaccination is restricted to individuals who are willing to pay. The aim of the current study was to evaluate the willingness and attitude of female university students in health schools/faculties in Jordan to get HPV vaccination and their knowledge about the virus. A self-administered online questionnaire was distributed in October 2021, which comprised 27 items to evaluate HPV knowledge, history of HPV vaccination, intentions to get the HPV vaccine, and the reason(s) behind vaccine refusal for those who rejected vaccination. The study sample comprised 836 participants: medical students (39.7%), pharmacy students (26.0%), dental students (21.2%), and nursing students (13.2%). Only 524 participants had heard of HPV prior to the study (62.7%), of which 48.7% knew about the availability of HPV vaccines. The lowest level of HPV knowledge was observed among nursing students. Only 19/524 students reported a history of HPV vaccination (3.6%). The overall willingness to receive HPV vaccination if provided freely was 75.0%, while only 16.0% were willing to pay for the vaccine. The most common reason for HPV vaccine rejection was the perceived low risk to get HPV infection. Significantly higher intentions to get HPV vaccination were found among older participants and medical students. The embrace of vaccine conspiracy beliefs was associated with a significantly less willingness to get the HPV vaccination (p < 0.001). Dependence on the internet/social media as the source of HPV knowledge was associated with a significantly lower intention to get HPV vaccination (p = 0.002). The coverage of the HPV vaccination among female university students in health schools in Jordan appeared extremely low; however, three-fourths of the students who had heard of HPV were willing to receive the HPV vaccination if provided freely. Complacency appeared as a major factor for HPV vaccine rejection. Increasing the levels of knowledge and awareness of HPV infection and its association with cervical cancer through reliable sources is recommended. This can be helpful for the individual benefit of the students besides the potentially positive role they can play in community education. Countering vaccine conspiracy beliefs with proper education and awareness programs can be helpful to appraise the role of HPV vaccines in cancer prevention. Full article

Waning of the mumps virus (MuV)-specific humoral response after vaccination has been suggested as a cause for recent mumps outbreaks in vaccinated young adults, although it cannot explain all cases. Moreover, CD8⁺ T cells may play an important role in the response against MuV; however, little is known about the characteristics and dynamics of the MuV-specific CD8⁺ T-cell response after MuV infection. Here, we had the opportunity to follow the CD8⁺ T-cell response to three recently identified HLA-A2*02:01-restricted MuV-specific epitopes from 1.5 to 36 months post-MuV infection in five previously vaccinated and three unvaccinated individuals. The infection-induced CD8⁺ T-cell response was dominated by T cells specific for the ALDQTDIRV and LLDSSTTRV epitopes, while the response to the GLMEGQIVSV epitope was subdominant. MuV-specific CD8⁺ T-cell frequencies in the blood declined between 1.5 and 9 months after infection. This decline was not explained by changes in the expression of inhibitory receptors or homing markers. Despite the ongoing changes in the frequencies and phenotype of MuV-specific CD8⁺ T cells, TCRβ analyses revealed a stable MuV-specific T-cell repertoire over time. These insights in the maintenance of the cellular response against mumps may provide hallmarks for optimizing vaccination strategies towards a long-term cellular memory response. Full article

Mass immunization of the citizens of the Republic of Serbia began in January 2021. Information on the significance, manner, advantages and consequences of this process was intensively distributed through all communication channels, with the media playing a key role. According to the data of the official institutions for the public health of Serbia, by July 2021 the lowest percentage of vaccinated population was among those between the ages of 18 and 24—only 15% of this demographic had received the vaccine by this point. Given the low turnout of young people for vaccination, in this paper we investigated the general attitude of students in Serbia, as a special category of young people, towards the vaccine against the COVID-19 virus, as well as their attitude regarding information about vaccination in the media. Research was conducted on a sample of 345 students at the University of Novi Sad. The results of the research showed that 42% of students had not been vaccinated and did not plan to do so, 37.4% had received at least one dose of vaccine and 20.6% had not been vaccinated even though they planned to do so. Students who were vaccinated had more confidence in information provided through media channels than those who were not vaccinated. Therefore, it can be concluded that encouraging students to decide in favor of vaccination against the COVID-19 virus should come from the universities where they study as well as the media. Full article

In Alberta, infectious laryngotracheitis virus (ILTV) infection is endemic in backyard poultry flocks; however, outbreaks are only sporadically observed in commercial flocks. In addition to ILTV vaccine revertant strains, wild-type strains are among the most common causes of infectious laryngotracheitis (ILT). Given the surge in live attenuated vaccine-related outbreaks, the goal of this study was to assess the efficacy of a recombinant herpesvirus of turkey (rHVT-LT) vaccine against a genotype VI Canadian wild-type ILTV infection. One-day-old specific pathogen-free (SPF) White Leghorn chickens were vaccinated with the rHVT-LT vaccine or mock vaccinated. At three weeks of age, half of the vaccinated and the mock-vaccinated animals were challenged. Throughout the experiment, weights were recorded, and feather tips, cloacal and oropharyngeal swabs were collected for ILTV genome quantification. Blood was collected to isolate peripheral blood mononuclear cells (PBMC) and quantify CD4+ and CD8+ T cells. At 14 dpi, the chickens were euthanized, and respiratory tissues were collected to quantify genome loads and histological examination. Results showed that the vaccine failed to decrease the clinical signs at 6 days post-infection. However, it was able to significantly reduce ILTV shedding through the oropharyngeal route. Overall, rHVT-LT produced a partial protection against genotype VI ILTV infection. Full article