With inputs from Dr Monica Vasudev

1047:  Human Challenge Trials for COVID-19 Vaccine and the Risk

Human challenge trials for the COVID-19 vaccine — These trials involve volunteering to receive an unproven vaccine, being exposed to the virus deliberately, instead of waiting to be exposed and for infection to occur naturally in the community.

The goal of such trials is to hasten vaccine development. Over 32,000 people from the United States and 139 other countries have signed up with an online registry, 1Day Sooner.

The trials could pave the way for delivering a vaccine and end the pandemic more quickly; however, there are several unknowns associated with this novel coronavirus, besides the lack of an effective treatment.The extra risk could come at a high cost – that of health, or potentially the life, of the volunteers.

These trials can be faster than conventional field trials, in part because fewer participants need to be exposed to provide early estimates of efficacy and safety.If one vaccine doesnt work, researchers can move on to other candidates. In challenge trials, volunteers are given the vaccine candidate or a placebo, just like conventional trials. After waiting for the vaccine to take effect, the volunteers are exposed to the virus.

While traditional vaccine trials may enrol 30,000 participants in phase 3 studies and have results in 6 months, challenge trials require only about 150 participants and obtain results in a period of 6 weeks. Several vaccine candidates can be compared at once through these trials and the most promising ones are subjected to larger studies.

Can a volunteer give informed consent when there are so many aspects that are unknown about COVID-19? According to clinicians, they would communicate the pros and cons if one of their patients ask about joining up.

According to the WHO, over the past 50 years, challenge studies have been safely conducted in thousands of consenting adult volunteers. The studies have helped ramp up the development of vaccines against cholera and typhoid and to assess immune protection against influenza.

Reducing even 1 day off vaccine development time could potentially save 7120 lives, according to estimates.

And reducing the development time by 3 months would go on to save more than a half million lives, according to estimates, considering that one sixth of the world would acquire COVID-19 annually and that a vaccine would prevent 0.2% of those people from dying.

Some experts note that the participants may include high-risk individuals who volunteer as they believe that the first vaccine attempts could prevent them from contracting COVID-19, a belief that may be termed "prevention misconception." [Medscape Excerpts]

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA