Theme 5: Experimental infection

Theme 5 of the PROTECT study is conducting experimental infections of both human volunteers and animals with SARS-CoV-2 to examine how they emit and transmit the virus, particularly in the early stages after infection.

This will answer key questions such as how big a dose of the virus is needed to infect people, and how long afterwards they are most infectious. The UK is the only country in the world conducting such human volunteer studies for COVID-19.

The volunteers themselves are young, healthy individuals at very low risk of becoming seriously ill from the infection, who stay in a contained and controlled hospital environment for the duration of their participation in the study. During this time, samples are taken from their nose, throat and breath, from the air and surfaces around them, and symptoms are recorded. Results are compared with those from the animal component of the study, which uses hamsters as the best small animal model for SARS-CoV-2 transmission.

Multiple variants of the virus, including the Delta variant, are being used in the study to identify differences in how they transmit. The infection of both vaccinated and unvaccinated volunteers is also planned.

Theme team

Theme lead: Professor Wendy Barclay, Imperial College London

Other partners:

  • Defence Science and Technology Laboratory
  • UK Health Security Agency
  • University of Leicester


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