Symptoms don't imply viral shedding in deliberate COVID-19 infection study

No serious adverse events occurred, and study model was shown to be safe and well tolerated.

The world's first "human challenge" trial, in which volunteers were purposefully exposed to the coronavirus, discovered that symptoms had no effect on the likelihood of an infected person spreading the disease to others. The findings highlight the difficulties of preventing community infections at a time when the World Health Organization (WHO) predicts an increase in cases. The research project, run by Open Orphan with Imperial College, London, showed that among the 18 participants that caught COVID-19, the severity of symptoms, or whether they developed symptoms at all, had nothing to do with the viral load in their airways. The viral load, or tendency to shed the virus, was determined using two methods: the focus-forming assay (FFA) and the quantitative polymerase chain reaction (qPCR).

"There was no correlation between the amount of viral shedding by qPCR or FFA and symptom score," the researchers said in paper published by scientific journal Nature Medicine. The Imperial trial exposed 36 healthy young adults who had never been infected or vaccinated to the original SARS-CoV-2 virus strain and observed them in a confined environment. In the end, two volunteers were determined to have antibodies to the virus and were thus excluded from the study. A little more than half of them became infected with the virus. According to the research team, no serious adverse events occurred, and the human challenge study model was shown to be safe and well tolerated in healthy young adults.