Context: In the race to develop a vaccine for the novel coronavirus, many people have volunteered to take part in the Human Challenge Trials (HCTs).It involves intentionally infecting volunteers with the novel coronavirus, in order to speed up the vaccination development.

Key Points

Vaccine Development

• In most of the regulatory regimes, vaccines take several years to develop and their development typically proceeds through three phases of clinical trials.
• Phase 1: Small groups of people receive the trial vaccine.
• Phase 2: Clinical study is expanded and the vaccine is given to people who have characteristics (such as age and physical health) similar to those for whom the new vaccine is intended.
• Phase 3: Vaccine is given to several thousand people and tested for efficacy and safety. During this phase, participants either receive the vaccine or a placebo.
• Placebo is anything which looks like real treatment but it is actually not. For example- sugar pills and saline injections.
• The vaccine’s efficacy is determined by comparing the prevalence of infection in the group that was administered the vaccine with the one which received a placebo.
• The hypothesis that those in the vaccine group will be infected significantly less is thus tested.

Human Challenge Trials

• Under HCTs, participants of both the vaccine group and placebo group are deliberately exposed to the infection after their consent and thus are challenged by the disease organism.
• HCTs are not new and they are usually carried out in developing medications for diseases which are considered less lethal and have been better understood by scientists over the years like malaria.

Few scientists have suggested replacing the conventional Phase 3 testing of vaccines by controlled HCTs of Covid-19 (SARS-CoV-2) vaccine which can accelerate the testing and potential rollout of efficacious vaccines.

• Such trials may reduce many months from the licensure process, making efficacious vaccines available more quickly and will also require significantly less number of people than regular Phase 3 trials.

Ethical Concerns

• While human challenge trials are not new, they are usually carried out in developing medications for diseases which are considered less lethal and have been better understood by scientists over the years, such as malaria.
• Critics have questioned undertaking such trials for Covid-19, which is potentially deadly and novel disease for even those who are less at risk. As per WHO: Such research can appear to be in conflict with the guiding principle in medicine to do no harm.

• HCTs for Covid-19 have been questioned by critics because it is a potentially deadly disease for even those who are less at risk, and has not been studied fully yet.
• In 2016, the WHO emphasised on the ethical framework of the challenge studies and also highlighted the importance of informed consent.
• Human challenge studies should be conducted with abundant forethought, caution, and oversight. The value of the information to be gained should clearly justify the risks to human subjects.
• Well documented historical examples of human exposure studies would be considered unethical by current standards.
• It is essential that challenge studies be conducted within an ethical framework in which truly informed consent is given.