COVID-19 vaccine: Could human challenge trials speed up the process?
Under these trials, scientists will infect healthy volunteers with the virus, to study the efficacy of their vaccines.
Challenging times call for heroic measures. Scientists are now mulling human challenge trials to speed up the process of making a viable COVID-19 vaccine. Under these trials, scientists will infect healthy volunteers with the virus, to study the efficacy of their vaccines.
To be sure, the vaccine trials for COVID-19 are already on a super-fast track: a vaccine is expected between 12-18 months compared with the 6-10 years that it normally takes to develop a vaccine. Indeed, some vaccine candidates have even reached the human trial phase in less than four months after the world learnt about a new “mystery” pneumonia virus. Many other potential vaccines are also in the pre-clinical or animal testing phase.
Of course, we now know that the virus is a type of severe acute respiratory syndrome coronavirus - or SARS-CoV-2. And the disease it causes, COVID-19, has already claimed 96,783 lives as of 4.30 pm IST on 10 April 2020.
Human challenge trials are done with super healthy volunteers, who are intentionally infected with the infectious microbe and then given the vaccine to see how effective it is. Though the process is not as simple as it sounds. There are many safety and ethical considerations along with some technical aspects that the research team considers - right from choosing the candidates, the exposure of the microbe these volunteers would get and the vaccine schedule.
Why human challenge trials
The main reason why scientists are proposing human trials is to be able to skip the most lengthy phase of vaccine development - the final phase of clinical trials that would require them to enrol thousands of volunteers and test vaccine safety and efficacy. Clinical trials have three phases with an increasing number of candidates.
Generally, even after a vaccine has crossed the final clinical trial phase, licencing and quality control takes a lot of time before the vaccine can be launched in the market and made available to the general public.
With human challenge trials, they would be able to skip the final phase of clinical trial and can apply for licencing quickly. This would significantly compress the timeline for developing the vaccine.
The proposed model for COVID-19 human challenge trial
A recent study published in the Journal of Infectious Diseases, the official (peer-reviewed) journal of the Infectious Disease Society of America, mentioned the proposed model for human challenge trials for COVID-19.
According to the paper, scientists will choose healthy young volunteers for this study who have never had exposure to the disease or the virus before and who are likely to get a milder infection. These volunteers will be randomly given doses of the vaccine or a placebo first and later a small amount of the SARS-CoV-2 virus.
After this, all the candidates will be monitored for the development of an immune response against the virus. This is to note if the healthy people who had the vaccine show a different immune response than those who got the placebo.
During the study, some volunteers may develop symptoms. So, all the candidates would be clinically monitored regularly for the viral load (quantity of the virus) in their body. If the viral load in a person increases too much or if the person has worsening symptoms they will start getting treatment for the disease. The viral load at which the person would be put on treatment will be set before beginning the study. The treatment would be priority-based, in state-of-the-art facilities to ensure that the volunteer recovers quickly and effectively. Until the infection is ruled out all the candidates would be kept in isolation.
All the volunteers would be told all about the study before enrolling so they know exactly what is being done. Only consenting candidates will be taken in.
If this test is successful, a placebo control study will be done in more than 1,000 at-risk candidates (without giving them the virus). This would help identify how the vaccine performs in the field and how safe it is in the long term.
For more information, read our article on How does COVID-19 spread?
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