The Volunteers who Challenge the Virus: Controlled Human Infections
By: Valentina Colapicchioni
Tags: Vaccines, Health, Research, Science, Clinical Trials

The Volunteers who Challenge the Virus: Controlled Human Infections

Would you be a volunteer who challenges the virus?

Photo by Obi Onyeador on Unsplash

In a time where everybody tries to protect themselves from COVID-19 — by wearing masks, respecting social distancing, or avoiding shared surfaces — some are facing the virus head-on!

Yes, thousands of people have expressed interest in participating in Controlled Human Infection (CHI) studies with SARS-CoV-2, the causative agent of COVID-19.

CHI studies aim to speed up the development of a vaccine for COVID-19. According to 1daysooner.org, a website that encourages people to volunteer to participate in human challenge trials or to advocate on their behalf, almost 30000 people from 140 countries have already applied to deliberately expose themselves to SARS-CoV-2. This is surprising, given that COVID-19 is like the “perfect” pandemic, it killed almost 500000 people worldwide and no specific treatments are available.

Why do these volunteers want to take on a life-threatening risk?

There are multiple reasons: some have strong motivations to help others, some people are motivated by the money while other volunteers are curious of the experience.

The perspective of one 41-year-old volunteer is very interesting, as the owner of a business that has him visiting warehouses and flying regularly, he figures he’ll inevitably get infected anyways, so he declared on CNN: “I feel if I did it under a controlled environment, and I had an adverse reaction, my chances are much better”.

On one hand, Dr. Lipsitch, a Harvard epidemiologist, confirmed that

“as a part of being in the trial they [partecipants] would be guaranteed excellent care if they needed it”.

On the other hand, controlled human infection studies continue to generate controversy within the scientific community especially from an ethical point of view.

It may seem impermissible to ask people to take on the risk of severe illness or death, even for an important collective gain.

To better understand the scientific doubts on this matter let’s start by defining controlled human infection studies.

In CHI studies, a small number of healthy participants are deliberately exposed to a known dose of a pathogen in a controlled setting, to study infection and gather preliminary efficacy data on experimental vaccines or treatments.

CHI studies, by allowing preliminary efficacy testing in 10–100 participants, are cheaper than phase 2 and 3 clinical trials that often require sample sizes ranging from hundreds to hundreds of thousands of participants. Thus, they help to identify inferior vaccine candidates or treatments before initiating large safety and efficacy trials, allowing valuable resources to be focused on those candidates that have the greatest potential for success.

CHI studies have emerged as powerful tools to select promising new vaccines or drugs on the increasingly complex and expensive path towards licensure. In this decade more than 120 controlled human infection studies have been published, primarily for influenza, rhinovirus, typhoid and malaria.

A malaria CHI study provided critical information for the development of the malaria vaccine RTS,S. Malaria CHI studies were performed to first evaluate the efficacy of this vaccine and to then further refine the formulation and dosing regimen before initiating Phase 3 efficacy evaluations in Africa.

A dengue CHI study was used to determine which formulation of a live-attenuated tetravalent dengue vaccine should be chosen to move forward in a Phase 3 efficacy trial in Brazil.