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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.)

Background: One third of children require repeat ventilation tube insertion (VTI) for otitis media. Disease recurrence is associated with persistent middle ear bacterial biofilms. With demonstration that Dornase alfa (a DNase) disrupts middle ear effusion biofilms ex vivo, we identified potential for this as an anti-biofilm therapy to prevent repeat VTI. First, safety and tolerability needed to be measured., Methods: This was a phase 1B double-blinded randomized control trial conducted in Western Australia. Children between 6 months and 5 years undergoing VTI for bilateral middle ear effusion were recruited between 2012 and 2014 and followed for two years. Children's ears were randomized to receive either Dornase alfa (1 mg/mL) or 0.9 % sodium chloride (placebo) at time of surgery. Children were followed up at 2 weeks post-VTI and at 3-monthly intervals for 2 years. Outcomes assessed were: 1) safety and tolerability, 2) otorrhoea frequency, 3) blocked or extruded ventilation tube (VT) frequency, 4) time to blockage or extrusion, 5) time to infection recurrence and/or need for repeat VTI., Results: Sixty children (mean age 2.3 years) were enrolled with 87 % reaching study endpoint. Treatment did not change otorrhoea frequency. Hearing improved in all children following VTI, with no indication of ototoxicity. Dornase alfa had some effect on increasing time until VT extrusion (p = 0.099); and blockage and/or extrusion (p = 0.122). Frequency of recurrence and time until recurrence were similar. Fourteen children required repeat VTI within the follow-up period., Conclusion: A single application of Dornase alfa into the middle ear at time of VTI was safe, non-ototoxic, and well-tolerated., Trial Registration: ACTRN12623000504617., Competing Interests: Declaration of competing interest There are no financial interests. Prof. Richmond serves on scientific advisory boards, and together with A/Prof Kirkham has received institutional funding for investigator-initiated grants, from GSK, Pfizer and MSD – all are unrelated to this work., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)