Dr Miriam Stoppard discusses how Brit scientists gained lots of insight into how quickly Covid infection takes root in a world-beating Challenge study
British scientists completed a world-beating challenge research on Covid. What is a challenge study?
It allows doctors to observe healthy people with Covid throughout the whole infection, something that’s not possible with Covid patients.
36 healthy young adults were monitored for coronavirus immunity in the study.
Participants aged 18-30 years, unvaccinated against Covid-19 and with no prior infection of the disease, were given a low dose of the virus – introduced via drops up the nose – and then carefully monitored in a controlled environment during a two-week period.
They were exposed to the lowest possible dose of virus to cause infection, roughly equivalent to the amount found in a single droplet of nasal fluid when someone was at their most infectious.
The Human Challenge Programme, a partnership between Imperial College London and the Vaccine Taskforce Department of Health and Social Care and Royal Free Hospital in London, is the Human Challenge Programme.
The virus causes symptoms to develop quickly, in the average of two days.
The infection starts in the throat, and peaks at five days – by which time it has become significantly more abundant in the nose.
This groundbreaking study by the Royal Free Hospital proved that experimental infection in volunteers can mimic real infections. It also laid the foundation for future challenges to new vaccines and medicines against Covid-19.
The average time between first exposure to the virus and the detection of early symptoms (incubation) took 42 hours. This is significantly shorter than the current estimates of five to six weeks.
Following this period there was a steep rise in the amount of virus (viral load) found in swabs taken from participants’ noses or throats, peaking at around five days.
There were many differences in the location of the most virus. The virus was first detected in the throat 40 hours earlier than the nose (compared to 58 hours for the nose).
Also, peak levels of virus were significantly higher in throat than in nose.
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This indicates a potentially greater risk of virus being shed from the nose than the mouth – hence the importance of proper face mask use to cover both these areas.
Professor Jonathan Van-Tam (ex-deputy chief medical officer) says: “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.”