What are the trials of human challenge? What can they tell us?

Representative image. | Photo credit: iStock Images

Key landmarks

  • Whether or not to administer a remedial drug or vaccine before or after delivery of the disease-causing agent is conditioned by the design of HCT
  • HCTs could, in theory, not only reveal rich information about how long a virus is needed to trigger an infection, but also about how the immune system has a natural defense and, potentially, which people will develop symptoms and which does not
  • HCT at Oxford University, according to Helen McShane, chief researcher and professor of vaccinology at the university, will seek to measure the levels of several components of the patient’s immune response, including T cells and antibodies.

Researchers at the University of Oxford in the UK will lead a new human challenge process to analyze the immune response needed to provide protection against COVID-19 reinfection, reports said on Monday.

The latest development comes after the first human challenge studies COVID-19 involving 90 healthy adult volunteers aged between 18 and 30, starting in late February this year, undertaken by scientists at Imperial College from London in collaboration with other institutions. Recruitment for the Oxford trial is expected to begin in the coming weeks.

What are the trials of human challenge?

According to the World Health Organization (WHO), human challenge studies (HCTs) are those “in which participants are intentionally challenged (whether or not they have been vaccinated) with an infectious disease organism. This challenge to the organism may be close to wild-type and pathogenic, adapted and / or attenuated to wild-type with less or no pathogenicity or genetically modified in any way. ”

In a typical Phase 1 study, a drug or vaccine is tested to determine its effectiveness without the subjects (study participants) being intentionally given the disease-causing agent. However, in an HCT, healthy volunteers are injected with the disease-causing agent to study their responses to it. Whether or not to administer a remedial drug or vaccine before or after administration of the disease-causing agent is conditioned by the design of HCT.

Proponents of HCT argue that these studies could be invaluable in saving time and money in developing more effective vaccines, as they will not have to rely on participants who contract COVID-19 infection in real conditions.

HCTs could, in theory, not only reveal rich information about how long a virus is needed to trigger an infection, but also about how the immune system organizes a natural defense and, potentially, which people will develop. symptoms and which not.

How will the Oxford University HCT work?

HCT from Oxford University, according to Helen McShane, chief researcher and professor of vaccinology at the university, will seek to measure the levels of several components of the patient’s immune response, including T cells and antibodies, while watching if participants become re-infected after have been exposed to the virus.

This, of course, will mean recruiting people who have already been infected with coronavirus at least three months before joining the trial. Participants must also be healthy, at low risk for COVID-19, aged 18 to 30 years, and have COVID-19 antibodies.

The first phase of HCT will see 24 participants divided into groups of three to eight who will be given a small dose of the initial nasal coronavirus strain. This dose may or may not be increased between groups, depending on what the process requires.

The second phase of the study, expected to begin in the summer, will include a completely new set of participants and analyze their immune response before and after exposure to the virus, while studying the level of infection and symptoms in those who become re-infected. If reinfection is confirmed or symptoms occur in both phases, patients will be given treatment with monoclonal antibodies.

“If we can determine the level of immune response beyond which an individual cannot be infected, then this will help us determine if new vaccines will be effective without necessarily testing them in the third phase of efficacy studies,” said McShane.

Participants will receive compensation of £ 5,000 for the full study, each of which will be quarantined for a period of at least 17 days during the trial. The follow-ups will take place over an additional 12 months.

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