This is a phase 1, dose-escalating study to evaluate the safety and immunogenicity of a single dose of either Ad5-triCoV/Mac, a replication deficient human adenovirus vector, or ChAd-triCoV/Mac, a replication deficient chimpanzee adenovirus 68 vector, delivered to the respiratory tract by aerosol, in healthy volunteers who have received at least three doses of an mRNA COVID-19 vaccine. Both vectors have been engineered to express the spike, nucleocapsid and RNA polymerase proteins.~Up to 36 healthy volunteers will be enrolled in this dose escalation study. The first cohort (n=6) will receive Ad5-triCoV/Mac (n=3) or ChAd-triCoV/Mac (n=3) at the lowest dose of 10e5 TCID50, administered using the AeroNeb Solo Vibrating Mesh Nebulizer. Assuming no safety concerns, participants will then be administered Ad5-triCoV/Mac (n=3) or ChAd-triCoV/Mac (n=3) at a dose of 10e6. Assuming no safety signals we will move to vaccinate at the next dose level of 1x10e7 TCID50. Decisions about dose escalation will be made independently for each vaccine based on safety and immunogenicity profile. If the immunogenicity endpoints are not reached, in the absence of a safety signal, at the 10e7 dose level, we will move to the next dose level of 3x10e7 TCID50 and enrol three participants/vaccine group. Similarly, if all of the immunogenicity endpoints in the BAL are not met at 3x10e7, and in the absence of any safety signal, we will further escalate to 1x10e8 TCID50 and enrol three participants/vaccine group, if required. For both vaccines the maximum dose level will be 1x10e8 TCID50.~Antibody and specific T cell responses will be measured in lung from bronchoalveolar lavage fluid collected at bronchoscopy at baseline and at 4 weeks following vaccination and in blood at several time points up to week 48 following vaccination.~Safety endpoints will include the nature of any adverse events, their severity and the probability of a relationship to study procedures and administration of vaccine.
This is a phase 1 study in healthy volunteers who have received at least three doses of an mRNA COVID-19 vaccine, to evaluate the safety and immune responses that develop in the blood and lungs following the administration by aerosol of either Ad5-triCoV/Mac or ChAd-triCoV/Mac, new experimental adenovirus-based vaccines expressing SARS-CoV-2 spike, nucleocapsid and RNA polymerase proteins.