Oxford to launch human challenge trial to study immune response

Caroline Nicolls receives an injection of the Modern Covid-19 vaccine administered by nurse Amy Nash, at the Madejski Stadium in Reading, west London, on April 13, 2021.

STEVE PARSONS | AFP | fake images

LONDON – Researchers at the University of Oxford announced on Monday the launch of a human challenge test to better understand what happens when people who have already contracted the coronavirus become infected a second time.

The researchers will examine what type of immune response could prevent people from being reinfected with Covid-19 and investigate how the immune system reacts to the virus a second time.

At present, little is known about what happens to people who have already had the virus when they are infected a second time.

The trial will take place in two phases, with different participants in each phase. The first phase is scheduled to begin this month and the second phase is due to begin in the summer.

In medical research, human provocation trials are controlled studies that involve deliberately exposing participants to a pathogen or insect to study the effects.

“Challenge studies tell us things that other studies cannot because, unlike natural infections, they are strictly controlled,” said Helen McShane, the study’s principal investigator and a professor of vaccinology in the Department of Pediatrics at the University of Oxford.

“When we reinfect these participants, we will know exactly how their immune systems have reacted to the first COVID infection, exactly when the second infection occurs, and exactly how much virus they have contracted,” McShane said.

The study is expected to help improve scientists’ basic understanding of the virus and help design tests that can reliably predict whether people are protected.

What happens in each phase?

For phase one, up to 64 volunteers between the ages of 18 and 30 who have previously been naturally infected will be re-exposed to the virus under controlled conditions.

Researchers will monitor participants’ care as they undergo CT scans of the lungs and MRIs of the heart while they are isolated in a specially designed suite for a minimum of 17 days.

Everyone who participates must be fit and well and must have fully recovered from their first Covid infection to minimize risk.

Trial participants will only be discharged from the quarantine unit when they are no longer infected and are at risk of spreading the disease.

A view of the city of London on a clear day.

Vuk Valcic | Images SOPA | LightRocket via Getty Images

The second phase of the trial will explore two different areas.

“First, we will define the baseline immune response in the volunteers very carefully, before infecting them. Then, we will infect them with the dose of virus chosen from the first study and measure the amount of virus that we can detect after infection. Then we can understand what kinds of immune responses protect against reinfection, “McShane said.

“Second, we will measure the immune response at various time points after infection so that we can understand what immune response the virus generates,” he added.

The total duration of the study will be 12 months, including a minimum of eight follow-up appointments after discharge.

“This study has the potential to transform our understanding by providing high-quality data on how our immune systems respond to a second infection with this virus,” said Shobana Balasingam, senior advisor for vaccine research at Wellcome, a charitable foundation that funds the study.

“The findings could have important implications for how we handle COVID-19 in the future, and inform not only vaccine development, but also research on the range of effective treatments that are also urgently needed,” Balasingam said.


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