This is a phase I dose escalation challenge study in which increasing titres of wild-type SARS-CoV-2 (1x10^1 TCID_50, 1x10^2TCID_50, 1x10^3TCID_50, 1x10^4TCID_50 and 1x10^5TCID_50) will be administered intranasally to different groups of volunteers in order to achieve a 50% (+/-10%) attack rate as determined by quantitative live viral detection and/or qPCR detection in naso-pharyngeal secretions at two consecutive 12 hourly time points (at least 24 hours after inoculation). Dose escalation will be capped at 10^5 TCID50 and we will proceed to dose confirmation, following DSMB safety review, even if we do not meet our target attack rate of 50% +/- 10%, to enable a larger sample size to assess the dynamic range of protection at that dose and ensure confidence in the negative infection rate at that dose.~A Data Safety Monitoring Board (DSMB) will review safety and quantitative virology at each dose level and will recommend continuation based on emergent data.~Rescue treatment with a single course of oral Paxlovid will commence immediately after any warning symptoms or signs of COVID-19 disease beyond mild disease.~Once the optimal dose of wildtype SARS-CoV-2 has been identified for previously infected volunteers and uninfected vaccinated volunteers (dose escalation groups 1 and 3), further challenge infections in groups 2 and 4 may proceed.~Volunteers will remain in isolation rooms within the clinical trials unit for a minimum of 14 days post inoculation and until demonstration of the absence of live virus in two sequential samples. All 4 groups will together enrol up to 132 volunteers.~This study will be funded by the Wellcome Trust and Department of Health and Social Care (DHSC).
A phase I, experimental dose finding, open label, clinical infection, safety and viral detection optimisation in previously SARS-CoV-2 infected (unvaccinated or vaccinated) or uninfected vaccinated volunteers.