Since the first human respiratory syncytial virus (HRSV) genotype classification in 1998, inconsistent conclusions have been drawn regarding the criteria that define HRSV genotypes and their nomenclature, challenging data comparisons between research groups. ‬‬‬‬‬‬‬‬‬In this study, we aim to unify the field of HRSV genotype classification by reviewing the different methods that have been used in the past to define HRSV genotypes and by proposing a new classification procedure, based on well-established phylogenetic methods. All available complete HRSV genomes (>12 000 base pairs) were downloaded from GenBank and divided into the two subgroups: HRSV-A and HRSV-B. From whole genome alignments, the regions that correspond to the open reading frame of the glycoprotein G and the second hypervariable region (HVR2) of the ectodomain were extracted. In the resulting partial alignments, the phylogenetic signal within each fragment was assessed. Maximum likelihood phylogenetic trees were reconstructed using the complete genome alignments. Patristic distances were calculated between all pairs of tips in the phylogenetic tree and summarized as a density plot in order to determine a cut-off value at the lowest point following the major distance peak. Our data shows that neither the HVR2 fragment, nor the G gene contains sufficient phylogenetic signal to perform reliable phylogenetic reconstruction. Therefore, whole genome alignments were used to determine HRSV genotypes. We define a genotype using the following criteria: a bootstrap support of ≥ 70% for the respective clade and a maximum patristic distance between all members of the clade of ≤ 0.018 substitutions per site for HRSV-A or ≤ 0.026 substitutions per site for HRSV-B. By applying this definition, we distinguish 23 genotypes within subtype HRSV-A and six genotypes within subtype HRSV-B. Applying the genotype criteria on subsampled datasets confirmed the robustness of the method.

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Hepatitis E virus (HEV) is one of the prime causes of acute viral hepatitis, and chronic hepatitis E is increasingly recognized as an important problem in the transplant setting. Nevertheless, the fundamental understanding of the biology of HEV replication is limited and there are few therapeutic options. The development of such therapies is partially hindered by the lack of a robust and convenient animal model. We propose the infection of athymic nude rats with the rat HEV strain LA-B350 as such a model. A cDNA clone, pLA-B350, was constructed and the infectivity of its capped RNA transcripts was confirmed in vitro and in vivo. Furthermore, a subgenomic replicon, pLA-B350/luc, was constructed and validated for in vitro antiviral studies. Interestingly, rat HEV proved to be less sensitive to the antiviral activity of α-interferon, ribavirin and mycophenolic acid than genotype 3 HEV (a strain that infects humans). As a proof-of-concept, part of the C-terminal polymerase sequence of pLA-B350/luc was swapped with its genotype 3 HEV counterpart: the resulting chimeric replicon replicated with comparable efficiency as the wild-type construct, confirming that LA-B350 strain is amenable to humanization (replacement of certain sequences or motifs by their counterparts from human HEV strains). Finally, ribavirin effectively inhibited LA-B350 replication in athymic nude rats, confirming the suitability of the rat model for antiviral studies.

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This abstract is a report of the investigations by a transdisciplinary team working on the ‘Vaccine Confidence’ challenge (Supplement 1). Since their introduction, vaccines have been one of the most successful health interventions in medicine. Prior to vaccination programs against poliomyelitis, more than 350,000 cases of polio were reported annually worldwide, a number that decreased to just 33 reported cases in 20181. Additionally, between 2000 and 2017, the measles vaccination program is estimated to have prevented 21.1 million deaths.2 However, in 2018 more than 19 million children under one year of age did not receive the recommended WHO vaccines.3 A recent rise in anti-vaccine or vaccination-hesitant mentalities has led to decreasing vaccine coverage in several Western countries. The WHO identified three C’s as main determinants of vaccine hesitancy, namely Complacency, Convenience in accessing vaccines, and Confidence. However, the term ‘vaccine hesitancy’ tends to be interpreted as a lack of confidence in vaccines and vaccinations for various reasons. Nevertheless, the goal of vaccination is to reach herd immunity by reaching a high vaccination coverage (90‐95% vaccinated) to stop the circulation of vaccine preventable diseases. We wanted to give equal attention to the three C’s as they are equally important in reaching herd immunity. <target target-type="page-num" id="p-116"/>Therefore, we chose to present the problem as a challenge of ‘vaccine coverage,’ rather than ‘vaccine hesitancy’ or ‘vaccine confidence’. In order to understand the complexity of the problem, we have developed a systems map which relates different global factors that impact an individual’s vaccination decision-making, as well as their likelihood of receiving vaccinations (Supplement 2). To create this map we assembled the information for the variables and connections from literature studies of peer-reviewed articles and interviews with stakeholders, kept anonymous, in the field of vaccination or healthcare (Supplements 3 & 4). This approach was selected as it provides a wide perspective that allows academics, governmental authorities, and lawmakers to better assess the various factors that affect vaccine coverage, and how they are related. The work leading to the map was presented to the public at a symposium (Supplement 5). Our map identifies essential factors such as psychology, education, economy, vaccine technology, political and environmental sphere, sources of information, and healthcare in order to understand what governs vaccination coverage. The map emphasizes how various factors and determinants are often interrelated, as opposed to the isolated factors described in previous literature. We identified important discrepancies between developed and developing countries regarding the factors that drive vaccine-related decision-making and availability. The systems map could ultimately serve as a tool to better understand the multifaceted problem of suboptimal vaccination coverage. Vaccine hesitancy as a threat to vaccination coverage is a complex and wicked problem with many underlying contributing factors, as has been depicted in our systems map on vaccine coverage. Our systems map allows more in-depth insights, not only into which factors are contributing, but also into the relationship between factors. Solving the decrease in vaccination coverage will require different types of solutions which can be developed by using a transdisciplinary approach.