First COVID-19 human challenge study yields infection clues

COVID-19 infection has a shorter incubation period than originally thought, and rapid tests performed well at tracking virus levels, a research team based at Imperial College London reported today in a preprint study that describes the results of the first human challenge trial.In other developments, a number of countries experiencing Omicron surges reported new record daily cases, while others nations that were affected earlier eased some of their measures.Infection starts in throat, peaks in noseWith the goals of exploring infection dynamics and whether the human challenge model is safe studying vaccines, treatments, and tests, Imperial College researchers conducted the study in young adults ages 18 to 30 who had not been vaccinated.

Participants were inoculated with nose drops containing a low dose of the original SARS-CoV-2 virus, then monitored in a controlled setting for 2 weeks.Eighteen experienced infections, including 16 who experienced symptoms, which were mild-to-moderate.

Common symptoms included stuffy or runny nose, sneezing, musculoskeletal pain, headache, fever, and fatigue. Thirteen had loss of taste or smell, which resolved after 3 months in all but three of the participants.None developed lung symptoms or suffered adverse events.

All will be monitored for 12 months to watch for any long-term effects.One key finding was a short incubation period of 42 hours, which is much less than the current estimate of 5 to 6 days.