Findings from the UK’s world-leading human challenge study provide new insights into mild infections with SARS-CoV-2 in healthy young adults.
www.imperial.ac.uk
Clinical insights
In the trial, 36 healthy male and female volunteers aged 18-30 years, unvaccinated against COVID-19 and with no prior infection with SARS-CoV-2 were given a low dose of the virus – introduced via drops up the nose – and then carefully monitored by clinical staff in a controlled environment over a two-week period. The study used virus from very early in the pandemic obtained from a hospitalized patient in the ISARIC4C study, prior to the emergence of the Alpha variant.
Eighteen of the volunteers became infected, 16 of whom went on to develop mild-to-moderate cold-like symptoms, including a stuffy or runny nose, sneezing, and a sore throat. Some experienced headaches, muscle/joint aches, tiredness and fever.
None developed serious symptoms. Two participants were excluded from the final analysis after developing antibodies between initial screening and inoculation.
Thirteen infected volunteers reported temporarily losing their sense of smell (anosmia), but this returned to normal within 90 days in all but three participants – the remainder continue to show improvement after three months.
There were no changes seen in their lungs, or any serious adverse events in any participant. All participants will be followed up for 12 months after leaving the clinical facility to monitor for any potential long-term effects.
Participants were exposed to the lowest possible dose of virus found to cause infection, roughly equivalent to the amount found in a single droplet of nasal fluid when participants were at their most infectious.
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