Randomised, double-blind, controlled phase 1 trial of the candidate tuberculosis vaccine ChAdOx1-85A delivered by aerosol versus intramuscular route

Background: A BCG booster vaccination administered via the respiratory mucosa may establish protective immune responses at the primary site of Mycobacterium tuberculosis infection. The primary objective of this trial was to compare the safety and immunogenicity of inhaled versus intramuscular administered ChAdOx1-85A. Methods: We conducted a single-centre, randomised, double-blind, controlled phase 1 study (Swiss National Clinical Trials Portal number SNCTP000002920). After a dose-escalation vaccination in nine BCGvaccinated healthy adults, a dose of 1 x 1010 vp of ChAdOx1-85A was administered to twenty BCG-vaccinated adults that were randomly allocated (1:1) into two groups: aerosol ChAdOx1-85A with intramuscular saline placebo or intramuscular ChAdOx1-85A with aerosol saline placebo, using block randomisation. A control group of ten BCG-na & iuml;ve adults received aerosol ChAdOx1-85A at the same dose. Primary outcomes were solicited and unsolicited adverse events (AEs) up to day 16 post-vaccination and Serious AEs (SAEs) up to 24 weeks; secondary outcomes were cell-mediated and humoral immune responses in blood and Findings: Both vaccination routes were well tolerated with no SAEs. Intramuscular ChAdOx1-85A was associated with more local AEs (mostly pain at the injection site) than aerosol ChAdOx1-85A. Systemic AEs occurred in all groups, mainly fatigue and headaches, without differences between groups. Respiratory AEs were not different between BCG-vaccinated groups. Aerosol ChAdOx1-85A vaccination induced Ag85A BAL and systemic cellular immune responses with compartmentalisation of the immune responses: aerosol ChAdOx1-85A induced stronger BAL cellular responses, particularly IFN gamma/IL17+CD4+ T cells; intramuscular ChAdOx1-85A induced stronger systemic cellular and humoral responses. Interpretation: Inhaled ChAdOx1-85A was well-tolerated and induced lung mucosal and systemic Ag85Aspecific T-cell responses. These data support further evaluation of aerosol ChAdOx1-85A and other viral vectors as a BCG-booster vaccination strategy. (c) 2024 The Author(s). Published by Elsevier Ltd on behalf of The British Infection Association. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).