Covid: what a study with intentionally infected volunteers revealed

The world’s first deliberate Covid-19 infection study offers new insights into the early stages of the disease.

The study gave a Covid load to 36 young, healthy, unvaccinated volunteers at the Royal Free hospital in London.

The results show where and when the virus takes hold in the body — and that some people resist infection.

Future studies of this type could help to develop the next generation of vaccines and drugs for Covid. They allow scientists to study the early stages of an infection, even before symptoms develop.

first symptoms

Each of the volunteers, ages 18 to 30, received an identical Covid viral load — equivalent to the amount in a single drop dropped from someone’s nose during the peak of Covid infection.

But only half of the volunteers were infected. The focus of future research should be to understand how the others – unvaccinated and lacking immunity from previous infections – resisted the virus.

In those who developed an infection, the virus took off quickly: the first symptoms and positive test results appeared in just 42 hours. The previous understanding was that the time from exposure to the virus to first symptoms is about five days.

The study also showed that although the virus settles in the throat, an even greater amount can be found in the nose, leading the researchers to emphasize the importance of wearing masks covering both.

“It’s a really unique study,” says immunologist Christopher Chiu, a professor at Imperial College London, UK.

The amount of virus peaked about five days after infection and remained detectable until 12 days later. Symptoms were mild, but some volunteers had a prolonged loss of smell.

“The Covid tests done in parallel with the volunteers had a good percentage of detection of the presence of the virus in sufficient quantity to infect other people”, says Chiu.

“Even if the tests are less sensitive on the first or second day of infection, if you use them correctly and repeatedly, and take action if they are positive, you can have a big impact on stopping the viral spread.”

strategic information

The virus used in the study was a variant taken from a patient early in the pandemic. New studies of the type should explore more recent variants.

The main finding – that it is relatively safe to carry out studies of deliberate infection – opens up new avenues of research.

Deliberate infection studies have produced advances in medicine, such as a new typhoid vaccine, and it is hoped that the same approach could lead to a new generation of Covid vaccines and antivirals.

The findings have been published online, but have not yet been peer-reviewed, that is, they have not been formally reviewed by other scientists;

“This important study has provided more important data about Covid-19 and how it spreads, which is invaluable in learning more about this new virus so we can fine-tune our response,” said Jonathan Van-Tam, the government’s chief medical adviser. from UK.