World's first Covid-19 human challenge study releases results

Results from the world’s first study that infected unvaccinated volunteers with Covid-19 in a controlled setting have been published.

Contract research organisation (CRO) Open Orphan announced the study in 2020, in partnership with hVIVO, Imperial College London, the Vaccine Taskforce and Department of Health and Social Care (CHSC), and the Royal Free London NHS Foundation Trust.

The study was designed to gain a greater insight into how Covid-19 progresses throughout the body following infection and assessed a range of factors including, incubation time, peak viral load, and the usability of lateral flow tests in determining a positive Covid-19 diagnosis.

The study infected 36 healthy male and female volunteers aged between 18-29 years with the original SARS-CoV-2 strain. Volunteers were monitored in a controlled quarantined setting at the Royal Free Hospital in London, where hVIVO clinicians collected data related to the disease’s progression.

Study results show that symptoms started to develop on average of about two days after contact with the virus and first appeared in the throat. Peak viral load was observed at five days into infection but was significantly more abundant in the nose than the throat – a finding the researchers say supports the use of mask wearing. More so, timelines of infection from the study show that viable virus levels were still seen after nine and 12 days in some volunteers, supporting the isolation periods advocated in most guidelines.

The researchers found that lateral flow tests (LFTs) were largely a good indicator of diagnosing someone with a Covid-19 infection. Modelling using study data show that regular asymptomatic LFTs would diagnose an infection before 70-80% of infectious virus had been generated. However, the tests were less effective in picking up lower levels of virus at the start and end of infection.

In terms of symptoms, volunteers largely experienced a mild-to-moderate cold, with others displaying stuffy noses, sneezing and a sore throat. Others experienced fatigue, headaches, fevers, and 13 volunteers experienced a loss of changed sense of smell.

Open Orphan state that the data supports the safety of the infection challenge model and could be used to provide a ‘'plug and play' platform for testing therapies and vaccines using the original Covid-19 strain as well as variants of the virus.

Open Orphan is now developing a Delta strain of the Covid-19 virus in partnership with Imperial College London which could be used in future trials.

Cathal Friel, executive chairman of Open Orphan, said: "I am delighted that the world's first Covid-19 characterisation study has completed with no serious adverse events or serious symptoms, demonstrating that a Covid-19 human challenge study is safe in healthy young adults. The results, which have been made public today, have provided invaluable insights into Covid-19 disease progression.

"Crucially, we have now successfully established a Covid-19 Human Challenge Model which could be instrumental in accelerating the development of future Covid-19 therapeutics. New variants, such as Omicron, often mean that vaccines and antivirals have to be quickly re-evaluated to ensure effectiveness. Human challenge studies could prove to be the fastest way to compare old and new vaccines and therapies."

Professor Sir Jonathan Van-Tam, Deputy Chief Medical Officer at Department of Health and Social Care, added: "Human challenge studies have been performed using other pathogens for decades, including flu and Respiratory Syncytial Virus (RSV). They need full independent ethical review and very careful planning - as has been the case this time. Every precaution is taken to minimise risk.

"Scientifically these studies offer real advantage because the timing of exposure to the virus is always known exactly, therefore things like the interval between exposure and the profile of virus shedding can be accurately described.

"This important study has provided further key data on Covid-19 and how it spreads, which is invaluable in learning more about this novel virus, so we can fine-tune our response. Challenge studies could still prove to be important in the future to speed the development of 'next-generation' Covid-19 vaccines and antiviral drugs.

"This data underline just how useful a tool lateral flow tests can be to pick up people when infectious and the importance of wearing a face covering in crowded, enclosed spaces."