Human Challenge Study Reveals Potentially Key COVID-19 Data

Medical Development Laboratory

U.K. scientists conducting the first human viral challenge on COVID-19 found that symptoms do not have any correlation to a person's ability to infect somebody else.

The landmark Human Challenge Programme, which was conducted by Open Orphan and Imperial College London, deliberately exposed 36 young and healthy participants ages 18 to 30 years old with no immunity to the SARS-CoV-2 virus over the course of 14 days. Once declared infected, they were placed under quarantine with close monitoring by a medical team at a section of London's Royal Free Hospital. This project is the first worldwide to perform detailed tracking over the virus' full course, from the point of infection until the virus is eliminated.

What is notable from the study is that although the participants developed symptoms at a rapid rate, about two days from contact with the virus on average, there appears to be no link between the speed by which a person gets symptoms and how severe the actual viral load. 

"Our study reveals some very interesting clinical insights, particularly around the short incubation period of the virus, extremely high viral shedding from the nose, as well as the utility of lateral flow tests, with potential implications for public health. People in this age group are believed to be major drivers of the pandemic and these studies, which are representative of mild infection," commented Professor Christopher Chiu, the chief investigator of the trial, in a statement

Lateral flow tests confirmed that an infectious virus was present and that the participants were contagious, but this did not demonstrate any relation with the symptoms. Still, LFTs have been proven to be a good predictor of whether or not a person can infect others.

"Even though in the first day or two they may be less sensitive, if you use them correctly and repeatedly, and act on them if they read positive, this will have a major impact on interrupting viral spread," Chiu added.

Of the 36 healthy volunteers that started with the trial, 18 had become infected, while 16 developed mild-to-moderate symptoms similar to a cold. None of them developed any serious symptoms, although two had later been excluded from the study after they were found to be developing antibodies from the time of initial screening to inoculation. Thirteen of those who were infected had temporarily lost their sense of smell, but this resolved itself within 90 days. All participants will be followed up for 12 months after exiting the facility to note if there are any effects in the long term.

The researchers are hoping to expand the study to include more participants to truly reflect on the greater population. Despite the limitations, however, industry experts see the findings as a good driver for public health initiatives, including isolation periods for those infected, proper wearing of face masks, using LFTs, and developing a broader and more targeted human challenge platform look into COVID-19 from various perspectives.

"While the characterization study was focused on the original SARS-CoV-2 strain, and there are differences in transmissibility between it and the other variants, the same factors will be responsible for protection against it, meaning the findings remain valuable for variants such as Delta or Omicron. These data provide a clear platform to now utilize the human challenge model to expedite product efficacy testing for new vaccines or antivirals," commented Dr. Andrew Catchpole, the chief scientific officer at hVIVO, a unit of Open Orphan, in the same release.

Details of the latest findings are published in the journal Nature.

Back to news