[Preprint] Safety, tolerability and viral kinetics during SARS-CoV-2 human challenge (2022) Killingley et al

This is the paper linked to the experiment of inoculating young adults with COVID early in 2020.

Abstract:

To establish a novel SARS-CoV-2 human challenge model, 36 volunteers aged 18-29 years without evidence of previous infection or vaccination were inoculated with 10 TCID50 of a wild-type virus (SARS-CoV-2/human/GBR/484861/2020) intranasally.

Two participants were excluded from per protocol analysis due to seroconversion between screening and inoculation. Eighteen (~53%) became infected, with viral load (VL) rising steeply and peaking at ~5 days post-inoculation.

Virus was first detected in the throat but rose to significantly higher levels in the nose, peaking at ~8.87 log10 copies/ml (median, 95% CI [8.41,9.53).

Viable virus was recoverable from the nose up to ~10 days post-inoculation, on average. There were no serious adverse events.

Mild-to-moderate symptoms were reported by 16 (89%) infected individuals, beginning 2-4 days post-inoculation.

Anosmia/dysosmia developed more gradually in 12 (67%) participants.

No quantitative correlation was noted between VL and symptoms, with high VLs even in asymptomatic infection, followed by the development of serum spike-specific and neutralising antibodies.

However, lateral flow results were strongly associated with viable virus and modelling showed that twice-weekly rapid tests could diagnose infection before 70-80% of viable virus had been generated.

Thus, in this first SARS-CoV-2 human challenge study, no serious safety signals were detected and the detailed characteristics of early infection and their public health implications were shown. ClinicalTrials.gov identifier: NCT04865237

Link to paper here
Link to the related Science article here

 

That's weird. Or maybe just the result of rigorous record-keeping. It wouldn't be much of a surprise if most "asymptomatic" cases are actually mild symptoms that people simply shrug off, or simply don't mention. Otherwise this is much higher than usually reported.