A dose finding human experimental infection study with SARS-CoV-2 Omicron BA.5 subvariant in healthy volunteers immunologically experienced against SARS-CoV-2

Healthy volunteers who have already been vaccinated against SARS-CoV-2 will be deliberately infected with the Omicron BA.5 virus to find the smallest dose that causes a mild, controlled reinfection. This matters because, as the virus evolves and immunity from vaccination or prior infection wanes, researchers need a safe way to study how the immune system responds to new variants. Current data from natural infections is messy—people are exposed at different times, with different viral loads, and often don’t know when they were infected. A controlled human infection model allows scientists to measure exactly what happens from the moment of exposure, in a group of people with known immune histories. If this study succeeds, it will provide a standardised tool for testing future vaccines and treatments against Omicron and related variants. Instead of waiting months for natural infection data during an outbreak, researchers could quickly assess whether a new vaccine blocks viral replication in the nose and throat—the key site of transmission. This could speed up the development of updated boosters and antiviral drugs, helping public health agencies stay ahead of emerging variants. The work is a practical step toward making respiratory virus challenge studies routine for pandemic preparedness.