Human challenge trials for Covid vaccine unnecessary, unethical — Fauci at ICMR symposium

While US infectious diseases expert Anthony Fauci said long-term effects of exposure to Covid are yet unknown, others said human challenge trials could quicken vaccine search.

Representative image | Miguel Á. Padriñán | Pexels

New Delhi: Conducting human challenge vaccine trials by deliberately exposing the live coronavirus to volunteers around the world is not necessary, and unethical, in the absence of proven treatments against the disease, said Anthony Fauci, one of the lead members of the Coronavirus Task Force in the US.

Fauci made the remarks at the Indian Council of Medical Research’s (ICMR) International Symposium on Novel Ideas in Science and Ethics of Vaccines against COVID-19 pandemic, an online symposium that was attended by global experts involved in vaccine development and distribution.

As part of his argument against such trials, he said while volunteers can be limited to those in the low fatality risk category, there is much that is still unknown about the disease, including its long-term effects.

Human challenge trials are clinical trials in which participants are intentionally infected with a disease, irrespective of whether they have been vaccinated. It is different from human trials, where volunteers are not deliberately exposed to the virus.

This disease-carrying organism may or may not be a modified version of the virus, but is usually not deadly. Human challenge studies have been conducted over hundreds of years, leading to advances in the development of drugs and vaccines.

Currently, no clinical trial is conducting human challenges for Covid-19.

Gagandeep Kang, who recently resigned as the executive director of the Translational Health Science and Technology Institute, said human challenge trials were never conducted in India but the government has been discussing the ethics around it in the context of Covid-19.

The ICMR has currently begun the process of conducting the traditional clinical trials for the indigenously developed vaccine candidate, Covaxin.

Human challenge trials versus clinical trials

About 125 academics, doctors, epidemiologists, scientists, and professors, including 15 Nobel laureates, wrote an open letter to the National Institutes of Health (NIH), a body under the US government, asking for human challenge trials to be conducted. They argued that the trials were necessary to address the urgent need for a vaccine to curb the pandemic.

“If challenge trials can safely and effectively speed the vaccine development process, there is a formidable presumption in favour of their use, which would require a very compelling ethical justification to overcome,” they wrote.

The Jenner Institute, which is working collaboratively on developing the promising vaccine candidate from University of Oxford, is considering such challenge trials to expedite results, according to a report in The Guardian.

Since exposure occurs in controlled laboratory settings, human challenge trials could potentially be completed in just a few weeks and require fewer people.

Currently, randomised control trials require a large number of volunteers to administer the vaccine candidate to, and are monitored over extended periods of time.

A control group is not given the vaccine so researchers can see if individuals in the vaccinated group contract the virus, and whether more people in the control group get infected than in the vaccinated group.

The results of the trial can be hard to decode, as physical distancing and other infection control measures prevent trial participants from being exposed to the virus.

After over three weeks of deliberations, members of the NIH’s Accelerating Covid-19 Therapeutic Interventions and Vaccines (ACTIV) Vaccines Working Group came to the conclusion that the risks of human challenge trials outweighed the benefits.

Argument against human challenge trials

Fauci said the high incidence of Covid-19 in the general population means that effective randomised controlled trials can be carried out.

He also pointed out that given that there are no proven treatments for Covid-19 at present, it is highly unethical to deliberately expose human volunteers to the virus.

He also said though such trials will be limited only to young participants who are at low risk of death, the long-term effects of exposure to the virus are yet unknown.

Fauci wasn’t the only expert to hold such a view. Peter Piot, director of the London School of Hygiene and Tropical Medicine who is also a recovered Covid patient, said he would not wish any one to be infected with the virus.

“Younger people may be at low risk of death, but it is not like they are not dying at all,” Piot said.

However, a number of experts participating in the symposium disagreed with the two.

Divided expert opinion

Stanley Plotkin, an American physician who works as a consultant to vaccine manufacturers, said human challenges play an important role in developing vaccines.

Pointing out that there are several advantages to such studies, he said human challenge trials can help quickly evaluate the efficacy on a case-to-case basis, and help understand the individual immune response in people.

Another advantage is that it can help compare different vaccines head to head, Plotkin said.

He also said there are now a number of promising treatments, which makes human challenge trials feasible for Covid-19.

“This has been done for other viruses like malaria and cholera without any problems, so I don’t see why we cannot do this for Covid-19,” said Adrian Hill, director of the Jenner Institute and professor of Human Genetics, University of Oxford.

Hill added that human challenge trials are also much cheaper and quicker. To ensure patient safety, protocol for conducting such studies can be put in place.

The other benefit to conducting these trials is that it will allow countries that are behind in the global vaccine race to accelerate their research, said Marc Lipstitch, an American epidemiologist at Harvard University. What it means is that such countries will not be left to  the mercy of “bully countries” for getting vaccine shots.

But Lipstitch also said human challenge trials should be used as an adjunct to larger clinical trials.

(An earlier version of this report stated that Gagandeep Kang had retired when she had, in fact, resigned as executive director of the Translational Health Science and Technology Institute. The error is regretted)