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Abstract Background The need for coronavirus 2019 (COVID-19) vaccination in different age groups and populations is a subject of great uncertainty and an ongoing global debate. Critical knowledge gaps regarding COVID-19 vaccination include the duration of protection offered by different priming and booster vaccination regimens in different populations, including homologous or heterologous schedules; how vaccination impacts key elements of the immune system; how this is modified by prior or subsequent exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and future variants; and how immune responses correlate with protection against infection and disease, including antibodies and effector and T cell central memory. Methods The Platform Trial In COVID-19 priming and BOOsting (PICOBOO) is a multi-site, multi-arm, Bayesian, adaptive, randomised controlled platform trial. PICOBOO will expeditiously generate and translate high-quality evidence of the immunogenicity, reactogenicity and cross-protection of different COVID-19 priming and booster vaccination strategies against SARS-CoV-2 and its variants/subvariants, specific to the Australian context. While the platform is designed to be vaccine agnostic, participants will be randomised to one of three vaccines at trial commencement, including Pfizer’s Comirnaty, Moderna’s Spikevax or Novavax’s Nuvaxovid COVID-19 vaccine. The protocol structure specifying PICOBOO is modular and hierarchical. Here, we describe the Core Protocol, which outlines the trial processes applicable to all study participants included in the platform trial. Discussion PICOBOO is the first adaptive platform trial evaluating different COVID-19 priming and booster vaccination strategies in Australia, and one of the few established internationally, that is designed to generate high-quality evidence to inform immunisation practice and policy. The modular, hierarchical protocol structure is intended to standardise outcomes, endpoints, data collection and other study processes for nested substudies included in the trial platform and to minimise duplication. It is anticipated that this flexible trial structure will enable investigators to respond with agility to new research questions as they arise, such as the utility of new vaccines (such as bivalent, or SARS-CoV-2 variant-specific vaccines) as they become available for use. Trial registration Australian and New Zealand Clinical Trials Registry ACTRN12622000238774. Registered on 10 February 2022.

Objectives: PICOBOO is a randomised, adaptive trial evaluating the immunogenicity, reactogenicity, and safety of COVID-19 booster strategies. Here, we present data for second boosters among individuals aged 18-<50 and 50-<70 years old primed with BNT162b2 until Day (D) 84., Methods: Immunocompetent adults who had received two doses of BNT162b2 and any licensed COVID-19 booster at least three months prior were eligible. Participants were randomly allocated to BNT162b2, mRNA-1273 or NVX-CoV2373 1:1:1. The log 10 concentration of anti-spike Ig Total was summarised as the geometric mean concentration (GMC). Reactogenicity and safety outcomes were captured., Results: Between Mar 2022 and Aug 2023, 743 participants were recruited to the trial and had D28 samples available. Of these, 120 and 103 belonged to the 18-<50 y and 50-<70 y strata, respectively. The mean adjusted GMCs (95% credible intervals) peaked at D28; these were 41 262 (31 611, 51 105), 45 585 (34 194, 57 441) and 25 281 (20 021, 31 234) U/mL in the 18-<50 y stratum and 30 753 (25 071, 36 704), 35 132 (27 523, 42 239) and 17 322 (13 983, 20 641) U/mL in the 50-<70 y stratum following BNT162b2, mRNA-1273 and NVX-CoV2373, respectively. Limited neutralisation against Omicron subvariants was found following boosting with all vaccines. There were 4 possibly or probably-related adverse events in the 18-<50 y stratum and 5 events in the 50-<70 y stratum, and severe reactogenicity events were <10% and <11% in these strata, respectively., Conclusions: Vaccines targeting Ancestral virus elicited boosted antibody responses to Ancestral virus but minimal neutralising antibody against Omicron variants., Competing Interests: Declaration of Competing Interest KF and TS are members of the Australian Technical Advisory Group on Immunisation (ATAGI) which advises the government on vaccine policy; their involvement as investigators on this trial has been declared to ATAGI. MP is involved in an ovarian cancer clinical trial that received funding from AstraZeneca. MP was involved in performing immunological assays on biological specimens obtained from participants in this trial, but was not involved in participant recruitment, data collection or the analysis of results. SNF leads the UK National Institute for Health and Care Research funded trial of third and fourth dose COVID-19 boosters. SNF acts on behalf of University Hospital Southampton NHS Foundation Trust, UK as an Investigator and/or providing consultative advice on clinical trials and studies of vaccines funded or sponsored by vaccine manufacturers including Moderna, Sanofi, Janssen, Pfizer, AstraZeneca, GlaxoSmithKline, Novavax, Seqirus, Medimmune, Merck and Valneva vaccines and antimicrobials. PR also reports acting on behalf of University of Western Australia, as an Investigator and/or providing consultative advice on clinical trials and studies of vaccines funded or sponsored by vaccine manufacturers including Moderna, Sanofi, Janssen, Pfizer, AstraZeneca, GlaxoSmithKline, Novavax, Seqirus, Merck and Clover Biopharmaceutical vaccines. HSM is an investigator on clinical vaccine trials funded by Industry. Her institution receives funding for investigator led research from Sanofi, Pfizer, Seqirus, and Moderna. UW is an Investigator for industry sponsored clinical vaccine trials. They receive no personal financial payment for this work. The other authors declare that they have no competing interests., (Copyright © 2024. Published by Elsevier Ltd.)

Objectives: PICOBOO is a randomised, adaptive trial evaluating the immunogenicity, reactogenicity, and safety of COVID-19 booster strategies. We report data for second boosters among individuals 50-<70 years old primed with AZD1222 (50-<70y-AZD1222) until Day 84., Methods: Immunocompetent adults who received any first booster ≥three months prior were eligible. Participants were randomly allocated to BNT162b2, mRNA-1273 or NVX-CoV2373 1:1:1. The concentrations of ancestral anti-spike immunoglobulin were summarised as the geometric mean concentrations (GMC). Reactogenicity and safety outcomes were captured. Additional analyses including neutralising antibodies were performed on a subset. ACTRN12622000238774., Results: Between Mar 2022 and Aug 2023, 743 participants were recruited and had D28 samples; 155 belonged to the 50-<70y-AZD1222 stratum. The mean adjusted GMCs (95% credible intervals) were 20,690 (17 555-23 883), 23,867 (20 144-27 604) and 8654 (7267-9962) U/mL at D28 following boosting with BNT162b2, mRNA-1273 and NVX-CoV2372, respectively, and 10,976 (8826-13 196), 15,779 (12 512-19 070) and 6559 (5220-7937) U/mL by D84. IgG against Omicron BA.5 was 2.7-2.9 times lower than the ancestral strain. Limited neutralisation against Omicron subvariants was found following all vaccines. Severe reactogenicity events were <4%., Conclusions: All vaccines were immunogenic with more rapid waning after mRNA vaccines. These data support boosting with vaccines with greater specificity for circulating Omicron subvariants., Competing Interests: Declaration of Competing Interest KF and TS are members of the Australian Technical Advisory Group on Immunisation (ATAGI), which advises the government on vaccine policy; their involvement as investigators on this trial has been declared to ATAGI. MP is involved in an ovarian cancer clinical trial that received funding from AstraZeneca. MP was involved in performing immunological assays on biological specimens obtained from participants in this trial, but was not involved in participant recruitment, data collection or the analysis of results. SNF leads the UK National Institute for Health and Care Research funded trial of third and fourth-dose COVID-19 boosters. SNF acts on behalf of University Hospital Southampton NHS Foundation Trust, UK, as an Investigator and/or providing consultative advice on clinical trials and studies of vaccines funded or sponsored by vaccine manufacturers including Moderna, Sanofi, Janssen, Pfizer, AstraZeneca, GlaxoSmithKline, Novavax, Seqirus, Medimmune, Merck and Valneva vaccines and antimicrobials. UW is an investigator on clinical trials of vaccines funded or sponsored by vaccine manufactures including Moderna, Sanofi, Pfizer, Merck and GlaxoSmithKline. PR also reports acting on behalf of University of Western Australia, as an Investigator and/or providing consultative advice on clinical trials and studies of vaccines funded or sponsored by vaccine manufacturers including Moderna, Sanofi, Janssen, Pfizer, AstraZeneca, GlaxoSmithKline, Novavax, Seqirus, Merck and Clover Biopharmaceutical vaccines. They receive no personal financial payment for this work. The other authors declare that they have no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objectives: Bacille Calmette-Guérin (BCG) vaccine has immunomodulatory effects that may provide protection against unrelated infectious diseases. We aimed to determine whether BCG vaccination protects adults against COVID-19., Design: Phase III double-blind randomised controlled trial., Setting: Healthcare centres in Australia, Brazil, the Netherlands, Spain, and the United Kingdom during the COVID-19 pandemic., Participants: 3988 healthcare workers with no prior COVID-19 and no contraindication to BCG., Intervention: Randomised 1:1 using a web-based procedure to receive a single 0.1 mL intradermal dose of BCG-Denmark (BCG group, n = 1999) or saline (placebo group, n = 1989)., Main Outcome Measures: Difference in incidence of (i) symptomatic and (ii) severe COVID-19 during the 12 months following randomisation in the modified intention to treat (mITT) population (confirmed SARS-CoV-2 naïve at inclusion)., Results: Of the 3988 participants randomised, 3386 had a negative baseline SARS-CoV-2 test and were included in the mITT population. The 12-month adjusted estimated risk of symptomatic COVID-19 was higher in the BCG group (22.6%; 95% confidence interval [CI] 20.6 to 24.5%) compared with the placebo group (19.6%; 95% CI 17.6 to 21.5%); adjusted difference +3.0% points (95% CI 0.2 to 5.8%; p = 0.04). The 12-month adjusted estimated risk of severe COVID-19 (mainly comprising those reporting being unable to work for ≥3 consecutive days) was 11.0% in the BCG group (95% CI 9.5 to 12.4%) compared with 9.6% in the placebo group (95% CI 8.3 to 11.1%); adjusted difference +1.3% points (95% CI -0.7 to 3.3%, p = 0.2). Breakthrough COVID-19 (post COVID-19 vaccination) and asymptomatic SARS-CoV-2 infections were similar in the two groups. There were 18 hospitalisations due to COVID-19 (11 in BCG group, 7 in placebo group; adjusted hazard ratio 1.56, 95% CI 0.60 to 4.02, p = 0.4) and two deaths due to COVID-19, both in the placebo group., Conclusions: Compared to placebo, vaccination with BCG-Denmark increased the risk of symptomatic COVID-19 over 12 months among healthcare workers and did not decrease the risk of severe COVID-19 or post-vaccination breakthrough COVID-19., Trial Registration: ClinicalTrials.gov NCT04327206., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The trial is financially supported by the Foundations listed in the Funding section. Authors disclose funding support over the past 36 months: National Health and Medical Research Council (NHMRC) Ideas Grant (NM), NHMRC Investigator Grant (NC), Melbourne Children’s Clinician-Scientist Fellowship Grant (KPP). Outside of the submitted work, JCr has received grants or contracts from Sanofi, MSD & CEPI; payment or honoraria for presentations from Pfizer and participates on Latin American data safety monitoring/advisory boards for mRNA-1273 (Modern/Zodiac), RSV maternal vaccine (Pfizer), Qdenga vaccine (Takeda) and Nirmatrelvir/Ritonavir-Paxlovid (Pfizer). KG is a member of the Royal Children’s Hospital (RCH) Human Research Ethics Committee (the primary ethics committee providing approval for the BRACE trial) and Director of Research Operations at RCH; she abstained from all discussion, voting, approval and review related to the BRACE trial. All other authors declare no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Gram-negative bloodstream infections (GNBSIs) more commonly occur in children with comorbidities and are increasingly associated with antimicrobial resistance. There are few large studies of GNBSIs in children that relate the clinical presentation, pathogen characteristics, and outcomes., Methods: A 3-year prospective study of GNBSIs in children aged <18 years was conducted in 5 Australian children's hospitals between 2019 and 2021. The clinical characteristics, disease severity, and outcomes were recorded. Causative pathogens underwent antibiotic susceptibility testing and whole genome sequencing., Results: There were 931 GNBSI episodes involving 818 children. Median age was 3 years (interquartile range, 0.6-8.5). A total of 576/931 episodes (62%) were community onset, though 661/931 (71%) occurred in children with comorbidities and a central venous catheter was present in 558/931 (60%). Central venous catheter (145/931) and urinary tract (149/931) were the most common sources (16% each). One hundred of 931 (11%) children required intensive care unit admission and a further 11% (105/931) developed GNBSIs in intensive care unit. A total of 659/927 (71%) isolates were Enterobacterales, of which 22% (138/630) were third-generation cephalosporin resistant (3GCR). Extended spectrum beta-lactamase genes were confirmed in 65/138 (47%) 3GCR Enterobacterales. Most common extended spectrum beta-lactamase genes were blaCTX-M-15 (34/94, 36%) and blaSHV-12 (10/94, 11%). There were 48 deaths overall and 30-day in-hospital mortality was 3% (32/931). Infections with 3GCR Enterobacterales were independently associated with higher mortality (adjusted odds ratio, 3.2; 95% confidence interval, 1.6-6.4)., Conclusions: GNBSIs in children are frequently healthcare associated and affect children younger than age 5 years. Infections with 3GCR Enterobacterales were associated with worse outcomes. These findings will inform optimal management guidelines and help prioritize future antimicrobial clinical trials., Competing Interests: Potential conflicts of interest . D. L. P. reports research grants from Shionogi, Pfizer, Merck, bioMérieux, BioVersys, Gilead, and consultancies with AMR Action Fund, CARB-X, Innoviva, Pfizer, Merck, bioMérieux, Cepheid, Aurobac, Arrepath, Spero, Shionogi. P. N. A. H. reports research grants from Gilead, has served on advisory boards for OpGen, Merck, and Sandoz, and has received honoraria from OpGen, Sandoz, Pfizer, and BioMérieux. S. C. H. W. has received honoraria for participation in MSD expert forum for pneumococcal disease, which was paid to Children's Health Queensland. U. W. received travel and accommodation support for meeting attendances by Pfizer and Moderna. A. D. I. has received honoraria for lectures from BioMérieux and Gilead that were paid to the University of Queensland. L. J. S. is a recipient of grants from Swiss National Science Foundation, Swiss Personalized Health Network (SPHN), NHMRC, NIH, NOMIS Foundation, Doris and Thomas Ammann Foundation. L. J. S. is also on the advisory board for the Lancet Child Adolescent Health Journal. HC receives grants from NIH and NIAID and payment from Merck for participation in Molnupiravir clinical trial. H. C. receives payment as senior editor for Sanford Guide to Antimicrobial Therapy and holds stocks in Moderna and Merck. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Background: Following reduction of public health and social measures concurrent with SARS-CoV-2 Omicron emergence in late 2021 in Australia, COVID-19 case notification rates rose rapidly. As rates of direct viral testing and reporting dropped, true infection rates were most likely to be underestimated., Objective: To better understand infection rates and immunity in this population, we aimed to estimate SARS-CoV-2 seroprevalence in Australians aged 0-19 years., Methods: We conducted a national cross sectional serosurvey from June 1, 2022, to August 31, 2022, in children aged 0-19 years undergoing an anesthetic procedure at eight tertiary pediatric hospitals. Participant questionnaires were administered, and blood samples tested using the Roche Elecsys Anti-SARS-CoV-2 total spike and nucleocapsid antibody assays. Spike and nucleocapsid seroprevalence adjusted for geographic and socioeconomic imbalances in the participant sample compared to the Australian population was estimated using multilevel regression and poststratification within a Bayesian framework., Results: Blood was collected from 2,046 participants (median age: 6.6 years). The overall adjusted seroprevalence of spike-antibody was 92.1% (95% credible interval (CrI) 91.0-93.3%) and nucleocapsid-antibody was 67.0% (95% CrI 64.6-69.3). In unvaccinated children spike and nucleocapsid antibody seroprevalences were 84.2% (95% CrI 81.9-86.5) and 67.1% (95%CrI 64.0-69.8), respectively. Seroprevalence was similar across geographic remoteness index and socioeconomic quintiles. Nucleocapsid antibody seroprevalence increased with age while the point seroprevalence of the spike antibody seroprevalence decreased in the first year of life and then increased to 97.8 (95% Crl 96.1-99.2) by 12-15 years of age., Conclusion: Most Australian children and adolescents aged 0-19 years, across all jurisdictions were infected with SARS-CoV-2 by August 2022, suggesting rapid and uniform spread across the population in a very short time period. High seropositivity in unvaccinated children informed COVID-19 vaccine recommendations in Australia., Competing Interests: All authors have no financial interests/personal relationships that may be considered as potential competing interests with this study. Some authors have received institutional research grants and travel funding from the Australian Government, non-government or private organisations for other bodies of work. Dr Archana Koirala, Professor Kristine Macartney and Professor Nicholas Wood declare funding support from the Australian Government Department of Health and Aged Care (DoHAC) to the institution National Centre for Immunisation Research and Surveillance (NCIRS). Dr Archana Koirala has received a travel and accommodation grant to present and attend the World Society of Paediatric Infectious Diseases scientific meeting in 2023. Professor Kristine Macartney received payment as an expert witness for Australian Health Departments against proceedings against COVID-19 health regulations in 2021-2022. Professor Kristine Macartney declares institutional directed funding support from the WHO and GAVI the Vaccine Alliance, Welcome Trust and the Australian NHMR, to NCIRS and the University of Sydney; payment as an expert witness for Australian health departments against proceedings against COVID-19 health regulations in 2021-2022, payment less than USD $5,000 for international travel for expert speaking engagements, non-pharmaceutical company sources. Professor Nicholas Wood, Professor Britta S von Ungern-Sternberg and Dr Brendan McMullan declare funding from the National Health and Medical Research Council (NHMRC) grants. Professor Britta S von Ungern-Sternberg declared funding support from Stan Perron Charitable Foundation. Professor Helen S Marshall declares a research grant from Pfizer to Women’s and Children’s Health Network (WCHN), no personal remuneration, for meningococcal research. Professor Peter Richmond declares research grants from Merck Sharpe & Dohme, GlaxoSmithKline (GSK) directed at the Telethon Kids Institute (TKI), no personal remuneration, on RSV, pneumococcal disease, varicella, meningococcal research and a COVID-19 vaccine study to assess immunogenicity and safety of homologous or heterologous vaccine schedules. Professor Peter Richmond, Professor Helen S Marshall and Professor Nicholas Wood declare a research grant from the Australian Government Department of Health and Aged Care to WCHN, TKI and University of Sydney for a COVID-19 DNA vaccine clinical trial Ms Alissa McMinn declares funding support from Pfizer provided support for flights/accommodation to attend the Public Health Association Australia Communicable Diseases & Immunisation Conference in 2023. Dr Ushma Wadia declares funding from Pfizer for flights and accommodation to attend Meningococcal Disease Vaccine Education in 2023. This does not alter our adherence to PLOS ONE policies on sharing data and materials., (Copyright: © 2024 Koirala et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Respiratory syncytial virus (RSV) reinfection in children is poorly understood. We examined the incidence, characteristics, and outcomes of hospital-attended RSV reinfections in children <16 years in Western Australia between 2012 and 2022. Individuals with repeat RSV detections ≥56 days apart were identified using laboratory data. The incidence of reinfection in the first five years of life was estimated using the total birth population from 2012 to 2017. Clinical data on a subset of reinfection episodes were obtained from two metropolitan pediatric centers. A total of 466 children with hospital-attended reinfections were identified. The median interval between RSV detections was 460 days (interquartile range: 324, 812), with a reinfection rate of 95 per 100,000 individuals (95% confidence interval: 82, 109). Reinfection was most common in children who experienced their first RSV detection <6 months of age. Predisposing factors were identified in 56% of children; children with predisposing factors were older at first and second detections, were more likely to be admitted, and had a longer length of stay. This study highlights the significant burden of hospital-attended RSV reinfections in children with and without predisposing factors. Expanded surveillance with in-depth clinical data is required to further characterize the impact of RSV reinfection.

BCG vaccination and revaccination are increasingly being considered for the protection of adolescents and adults against tuberculosis and, more broadly, for the off-target protective immunological effects against other infectious and noninfectious diseases. Within an international randomized controlled trial of BCG vaccination in healthcare workers (the BRACE trial), we evaluated the incidence of local and serious adverse events, as well as the impact of previous BCG vaccination on local injection site reactions (BCG revaccination). Prospectively collected data from 99% (5351/5393) of participants in Australia, Brazil, Spain, The Netherlands and the UK was available for analysis. Most BCG recipients experienced the expected self-limiting local injection site reactions (pain, tenderness, erythema, swelling). BCG injection site itch was an additional common initial local symptom reported in 49% of BCG recipients. Compared to BCG vaccination in BCG-naïve individuals, BCG revaccination was associated with increased frequency of mild injection site reactions, as well as earlier onset and shorter duration of erythema and swelling, which were generally self-limiting. Injection site abscess and regional lymphadenopathy were the most common adverse events and had a benign course. Self-resolution occurred within a month in 80% of abscess cases and 100% of lymphadenopathy cases. At a time when BCG is being increasingly considered for its off-target effects, our findings indicate that BCG vaccination and revaccination have an acceptable safety profile in adults.

The prevalence of scar formation following Bacille Calmette-Guérin (BCG) vaccination varies globally. The beneficial off-target effects of BCG are proposed to be stronger amongst children who develop a BCG scar. Within an international randomised trial ('BCG vaccination to reduce the impact of coronavirus disease 2019 (COVID-19) in healthcare workers'; BRACE Trial), this nested prospective cohort study assessed the prevalence of and factors influencing scar formation, as well as participant perception of BCG scarring 12 months following vaccination . Amongst 3071 BCG-recipients, 2341 (76%) developed a BCG scar. Scar prevalence was lowest in Spain and highest in UK. Absence of post-injection wheal (OR 0.4, 95%CI 0.2-0.9), BCG revaccination (OR 1.7, 95%CI 1.3-2.0), female sex (OR 2.0, 95%CI 1.7-2.4), older age (OR 0.4, 95%CI 0.4-0.5) and study country (Brazil OR 1.6, 95%CI 1.3-2.0) influenced BCG scar prevalence. Of the 2341 participants with a BCG scar, 1806 (77%) did not mind having the scar. Participants more likely to not mind were those in Brazil, males and those with a prior BCG vaccination history. The majority (96%) did not regret having the vaccine. Both vaccination-related (amenable to optimisation) and individual-related factors affected BCG scar prevalence 12 months following BCG vaccination of adults, with implications for maximising the effectiveness of BCG vaccination., (© 2023 The Authors.)

Background: The need for coronavirus 2019 (COVID-19) vaccination in different age groups and populations is a subject of great uncertainty and an ongoing global debate. Critical knowledge gaps regarding COVID-19 vaccination include the duration of protection offered by different priming and booster vaccination regimens in different populations, including homologous or heterologous schedules; how vaccination impacts key elements of the immune system; how this is modified by prior or subsequent exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and future variants; and how immune responses correlate with protection against infection and disease, including antibodies and effector and T cell central memory., Methods: The Platform Trial In COVID-19 priming and BOOsting (PICOBOO) is a multi-site, multi-arm, Bayesian, adaptive, randomised controlled platform trial. PICOBOO will expeditiously generate and translate high-quality evidence of the immunogenicity, reactogenicity and cross-protection of different COVID-19 priming and booster vaccination strategies against SARS-CoV-2 and its variants/subvariants, specific to the Australian context. While the platform is designed to be vaccine agnostic, participants will be randomised to one of three vaccines at trial commencement, including Pfizer's Comirnaty, Moderna's Spikevax or Novavax's Nuvaxovid COVID-19 vaccine. The protocol structure specifying PICOBOO is modular and hierarchical. Here, we describe the Core Protocol, which outlines the trial processes applicable to all study participants included in the platform trial., Discussion: PICOBOO is the first adaptive platform trial evaluating different COVID-19 priming and booster vaccination strategies in Australia, and one of the few established internationally, that is designed to generate high-quality evidence to inform immunisation practice and policy. The modular, hierarchical protocol structure is intended to standardise outcomes, endpoints, data collection and other study processes for nested substudies included in the trial platform and to minimise duplication. It is anticipated that this flexible trial structure will enable investigators to respond with agility to new research questions as they arise, such as the utility of new vaccines (such as bivalent, or SARS-CoV-2 variant-specific vaccines) as they become available for use., Trial Registration: Australian and New Zealand Clinical Trials Registry ACTRN12622000238774. Registered on 10 February 2022., (© 2023. Crown.)

Introduction: Influenza vaccination of children with medical comorbidities is critical due their increased risks for severe influenza disease. In Australia, hospitals are an avenue for influenza vaccine delivery to children with comorbidities but are not always effectively utilised. Qualitative enquiry sought to ascertainment the barriers and enablers for influenza vaccination recommendation, delivery, and recording of these children at Australian hospitals., Methods: Semi-structured interviews and discussion group sessions were conducted with paediatricians and nurses at four tertiary paediatric specialist hospitals and two general community hospitals in three Australian states. Transcripts from interviews and group sessions were inductively analysed for themes. The Capability, Opportunity, Motivation, and Behaviour (COM-B) model was used to explore the elements of each theme and identify potential interventions to increase influenza vaccination recommendation and delivery behaviours by providers., Results: Fifteen discussion sessions with 28 paediatricians and 26 nurses, and nine in-depth interviews (five paediatricians and four nurses) were conducted. Two central thematic domains were identified: 1. The interaction between hospital staff and parents/patients for influenza vaccine recommendation, and 2. Vaccination delivery and recording in the hospital environment. Six themes across these domains emerged detailing the importance of dedicated immunisation services, hospital leadership, paediatricians' vaccine recommendation role, the impact of comorbidities, vaccination recording, and cocooning vaccinations. Supportive hospital leadership, engaged providers, and dedicated immunisation services were identified as essential for influenza vaccination of children with comorbidities in Australian hospital., Conclusion: Recommendation of influenza vaccination for Australian children with comorbidities is impacted by the beliefs of paediatricians and the perceived impact of influenza disease on children's comorbidities. Dedicated immunisation services and supportive hospital leadership were drivers for influenza vaccine delivery at hospitals. Future interventions targeting hospital-based influenza vaccine delivery for children with comorbidities should take a rounded approach targeting providers' attitudes, the hospital environment and leadership support., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: A/Prof Seale has previously received funding from vaccine manufactures for investigator driven research and for presenting at workshops. This funding was not associated with this research and this does not alter our adherence to PLOS ONE policies on sharing data and materials. All other authors have no competing interests to declare. All authors have approved submission of the manuscript for publication to PLOS ONE., (Copyright: © 2022 Norman et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: With the emergence of novel vaccines and new applications for older vaccines, co-administration is increasingly likely. The immunomodulatory effects of BCG could theoretically alter the reactogenicity of co-administered vaccines. Using active surveillance in a randomised controlled trial, we aimed to determine whether co-administration of BCG vaccination changes the safety profile of influenza vaccination., Methods: Participants who received influenza vaccine alone (Influenza group) were compared with those who also received BCG-Denmark vaccine in the contralateral arm (Influenza+BCG group). Data on the influenza vaccination site were collected using serial questionnaires and active follow-up for 3 months post vaccination., Results: Of 1351 participants in the Influenza+BCG group and 1418 participants in the Influenza group, 2615 (94%) provided influenza vaccine safety data. There was no significant difference in the proportion of participants with any local adverse reaction between the Influenza+BCG group and the Influenza group (918/1293 [71.0%] versus (906/1322 [68.5%], p = 0.17). The proportion of participants reporting any pain, erythema and tenderness at the influenza vaccination site were similar in both groups. Swelling was less frequent (81/1293 [6.3%] versus 119/1322 (9.0%), p = 0.01) and the maximal diameter of erythema was smaller (mean 1.8 cm [SD 2.0] versus 3.0 cm [SD 2.5], p<0.001) in the Influenza+BCG group. Sixteen participants reported serious adverse events: 9 participants in the Influenza+BCG group and 7 in the Influenza group., Conclusions: Adverse events following influenza vaccination are not increased when BCG is co-administered., Competing Interests: The authors have declared that no competing interests exist.

Introduction: The Australian Technical Advisory Group on Immunisation and New Zealand Ministry of Health recommend all children aged ≥ 5 years receive either of the two mRNA COVID-19 vaccines: Comirnaty (Pfizer), available in both Australia and New Zealand, or Spikevax (Moderna), available in Australia only. Both vaccines are efficacious and safe in the general population, including children. Children and adolescents undergoing treatment for cancer and immunosuppressive therapy for non-malignant haematological conditions are particularly vulnerable, with an increased risk of severe or fatal COVID-19. There remains a paucity of data regarding the immune response to COVID-19 vaccines in immunosuppressed paediatric populations, with data suggestive of reduced immunogenicity of the vaccine in immunocompromised adults., Recommendations: Considering the safety profile of mRNA COVID-19 vaccines and the increased risk of severe COVID-19 in immunocompromised children and adolescents, COVID-19 vaccination is strongly recommended for this at-risk population. We provide a number of recommendations regarding COVID-19 vaccination in this population where immunosuppressive, chemotherapeutic and/or targeted biological agents are used. These include the timing of vaccination in patients undergoing active treatment, management of specific situations where vaccination is contraindicated or recommended under special precautions, and additional vaccination recommendations for severely immunocompromised patients. Finally, we stress the importance of upcoming clinical trials to identify the safest and most efficacious vaccination regimen for this population., Changes in Management as a Result of This Statement: This consensus statement provides recommendations for COVID-19 vaccination in children and adolescents aged ≥ 5 years with cancer and immunocompromising non-malignant haematological conditions, based on evidence, national and international guidelines and expert opinion., Endorsed by: The Australian and New Zealand Children's Haematology/Oncology Group., (© 2022 AMPCo Pty Ltd.)

Background: Status epilepticus is associated with significant morbidity and mortality. While vaccine-proximate status epilepticus (VP-SE) has rarely been associated with cases of Dravet syndrome, it is not known whether VP-SE differs clinically from non-vaccine proximate status epilepticus (NVP-SE)., Methods: Medical records of children aged ≤24 months, presenting to one of five Australian tertiary pediatric hospitals with their first episode of status epilepticus from 2013 to 2017 were identified using ICD-coded discharge diagnoses. Vaccination history was obtained from the Australian Immunisation Register. Hospitalization details, subsequent epilepsy diagnosis, and vaccination uptake were compared between VP-SE and NVP-SE cases., Results: Of 245 first status epilepticus hospitalization with immunization records, 35 (14%) were VP-SE and 21 (60%) followed measles-containing vaccines. Vaccine-proximate status epilepticus cases had a median age of 12.5 months [IQR 7.1-14.73], 23 (66%) were in males, 15 (43%) were febrile status epilepticus and 17 (49%) had an infection confirmed. There were no significant differences in hospitalization duration (P = 0.50) or intensive care unit admission (P = 0.42) between children with VP-SE compared to children with NVP-SE. Children with no history of seizures at their first VP-SE had longer hospitalizations, were more likely to require intensive care unit admission, but were less likely to have a subsequent diagnosis of epilepsy than children with previous seizures at their first VP-SE., Conclusion: First VP-SE was predominantly associated with a measles-containing vaccine at 12-months of age. Seizure severity was no different between first VP-SE and first NVP-SE. In children with VP-SE, subsequent seizure admissions and epilepsy diagnosis were associated with having seizure prior to their first SE., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2022. Published by Elsevier Inc. All rights reserved.)

The reported frequency and types of adverse events following initial vaccination and revaccination with Bacille Calmette-Guérin (BCG) varies worldwide. Using active surveillance in a randomised controlled trial of BCG vaccination (the BRACE trial), we determined the incidence and risk factors for the development of BCG injection site abscess and regional lymphadenopathy. Injection site abscess occurred in 3% of 1387 BCG-vaccinated participants; the majority (34/41, 83%) resolved without treatment. The rate was higher in BCG-revaccinated participants (OR 3.6, 95% CI 1.7-7.5), in whom abscess onset was also earlier (median 16 vs. 27 days, p = 0.008). No participant with an abscess had a positive interferon-gamma release assay. Regional lymphadenopathy occurred in 48/1387 (3%) of BCG-vaccinated participants, with a higher rate in revaccinated participants (OR 2.1, 95% CI 1.1-3.9). BCG-associated lymphadenopathy, but not injection site abscess, was influenced by age and sex. A previous positive tuberculin skin test was not associated with local reactions. The increased risk of injection site abscess or lymphadenopathy following BCG revaccination is relevant to BCG vaccination policy in an era when BCG is increasingly being considered for novel applications., (© 2022. The Author(s).)

Background: Seizures, whether febrile or afebrile, occurring within 14 days following vaccination can be considered as vaccine proximate seizures (VPSs). While the attributable risk and clinical severity of first febrile VPS is well known, the risk and clinical outcomes of VPS recurrence is less well defined., Methods: We conducted a retrospective review of revaccination management and outcomes in children who experienced a VPS as their first seizure seen in Australian Specialist Immunisation Clinics between 2013 and 2017. Vaccination outcomes were compared between children who had a VPS as their only seizure (VPS only) and children who had further non-vaccine proximate seizures following their initial VPS (VPS+) prior to review at the clinic., Results: We identified 119 children with a VPS as their first seizure, of which 61 (51%) went on to have other seizures (VPS+). Children with VPS+ were more likely to present at a younger age (6.2 vs 12.5 months, P = 0.03), with afebrile seizures (42.6% vs 15.5%, P = 0.002) compared to VPS only children. VPS recurrence on revaccination was uncommon in both groups, but more common in VPS+ children (12.5% vs 2.4%, P = 0.07). Having an epilepsy diagnosis, specifically Dravet syndrome, was associated with VPS recurrence (P < 0.001). Of the four children with Dravet syndrome who had VPS recurrence, all had status epilepticus following revaccination., Conclusion: In children who presented with a single VPS as their only seizure, VPS recurrence on revaccination was uncommon. Children who had multiple non-vaccine proximate seizures following their initial VPS (VPS+) were more likely to present with afebrile VPS, at a younger age and have a VPS recurrence with vaccination. In these children, particularly those aged < 12 months, assessment and investigation for diagnosis of Dravet syndrome should be considered and additional precautions for revaccination undertaken as they are at highest risk of VPS recurrence., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2021. Published by Elsevier Ltd. All rights reserved.)

Vitamin D deficiency is highly prevalent in newly settled refugees in Western Australia (WA). If adherence to daily vitamin D therapy is problematic, depot therapy is a therapeutic alternative. The aim of this study was to compare daily versus depot treatment and factors influencing the therapeutic outcome. Newly settled refugees ( n = 151) with 25(OH)D levels less than 78 nmol/L were randomised to receive daily or depot vitamin D therapy with eight weekly interval follow up to 40 weeks. Biochemical and clinical parameters were collected at each visit. Generalized Linear Mixed Models (GLMM) examined the longitudinal changes over time controlling for confounders including age, gender, treatment arm, season, country of refuge/origin and sun exposure score. Participants were aged 5.5 months to 16.0 years (75 males, 83 females). Both treatment groups achieved vitamin D sufficiency. The daily treatment group had significantly higher 25(OH)D levels at each visit post baseline and a higher proportion of participants with levels above 50 nmol/L at all time points. Time, treatment group, calcium and sun exposure score were significant predictors of 25(OH)D serum levels. Depot vitamin D therapy is an alternative to daily treatment in this at-risk group of children and adolescents in whom treatment adherence is problematic., Competing Interests: The authors declare no conflict of interest.

Context: In the ongoing influenza pandemic, a safe and effective vaccine against 2009 influenza A(H1N1) is needed for infants and children., Objective: To assess the immunogenicity and safety of a 2009 influenza A(H1N1) vaccine in children., Design, Setting, and Participants: Randomized, observer-blind, age-stratified, parallel group study assessing 2 doses of an inactivated, split-virus 2009 influenza A(H1N1) vaccine in 370 healthy infants and children aged 6 months to less than 9 years living in Australia., Intervention: Intramuscular injection of 15 microg or 30 microg of hemagglutinin antigen dose of monovalent, unadjuvanted 2009 influenza A(H1N1) vaccine in a 2-dose regimen, administered 21 days apart., Main Outcome Measures: Hemagglutination inhibition assay to estimate the proportion of participants with antibody titers of 1:40 or greater, seroconversion, or a significant antibody titer increase, and factor increase in geometric mean titer. Assessments of solicited adverse events during 7 days and unsolicited adverse events for 21 days after each vaccination., Results: Following the first dose of vaccine, antibody titers of 1:40 or greater were observed in 161 of 174 infants and children in the 15-microg group (92.5%; 95% confidence interval [CI], 87.6%-95.6%) and in 168 of 172 infants and children in the 30-microg group (97.7%; 95% CI, 94.2%-99.1%). Corresponding seroconversion rates were 86.8% (95% CI, 80.9%-91.0%) and 94.2% (95% CI, 89.6%-96.8%), and factor increases in geometric mean titer were 13.6 (95% CI, 11.8-15.6) and 18.3 (95% CI, 15.7-21.4). All participants demonstrated antibody titers of 1:40 or greater after the second vaccine dose. Immune responses were robust regardless of age, baseline serostatus, or seasonal influenza vaccination status. The majority of adverse events were mild to moderate in severity., Conclusion: One 15-microg dose of vaccine was immunogenic in infants and children starting at 6 months of age and vaccine-associated reactions were mild to moderate in severity., Trial Registration: clinicaltrials.gov Identifier: NCT00940108.