working-of-the-human-challenge-summary

Context: At a time when the whole world is focused on fighting against COVID-19, more than 20,000 people from 102 countries have enrolled on a US website to voluntarily infect themselves with the virus.

More about the news:

  • The objective of this human challenge is to go on to test whether a given vaccine works on any of these infected persons. 
  • Lawmakers in the US have been pushing for human challenge trials and the World Health Organization (WHO) has given the go-ahead, subject to a set of preconditions being met.
  • Status of developments of vaccine against COVID-19:
    • Currently there are over 100 vaccine molecules under various stages of development across the world. 
    • At least two, one by researchers at Oxford University and another Hong Kong-listed biotech firm CanSino Biologics, are already in Phase II clinical trials.

Human challenge studies and their importance

  • Controlled human infection studies (or ‘human challenge studies’) involve the deliberate infection of healthy volunteers
  • Human challenges expedite trials because a lot of time may be lost waiting for a trial subject to contract the disease naturally from the community.
  • Also if infection does not happen normally, it is difficult to find out whether it is because of the vaccine or whether it is because the person was never exposed at all.
  • Such studies can be particularly valuable for testing vaccines
    • They can be substantially faster to conduct than vaccine field trials, in part because far fewer participants need to be exposed to experimental vaccines in order to provide (preliminary) estimates of efficacy and safety. 
    • Such studies can be used to compare the efficacy of multiple vaccine candidates and thus select the most promising vaccines for larger studies.

Earlier uses of Human challenge trials

  • Human challenge trials are routinely done for diseases such as malaria, dengue, influenza and cholera which extract a heavy public health toll but are not otherwise deadly.
  • The first well-described influenza challenge study was published in 1937 and involved the inhalation of a human influenza virus.
  • WHO says that in the last 50 years, challenge studies have been performed safely in tens of thousands of consenting adult volunteers under the oversight of research ethics committees. 

Addressing ethical Concerns:

  • It is important to choose volunteers with care, with full disclosure is given and informed consent sought from them, before going ahead with the actual act of infection.
  • WHO guidelines:
    • Challenge studies are ethically sensitive and must be carefully designed and conducted in order to minimize harm to volunteers and preserve public trust in research. 
    • In particular, investigators need to adhere to standard research ethics requirements.
  • Utilising less risky population group:
    • WHO estimates that participation in COVID-19 challenge studies would be the least risky for young healthy adults. 
    • In ages 18-30 years (whether healthy or not), hospitalisation rates for Covid-19 are currently estimated to be around 1% and fatal infection rates around 0.03%.

Tackling the threat of COVID-19

  • There is currently no approved treatment against COVID. This means that there are only two ways of tackling the threat of COVID-19.
    • Herd Immunity
      • When a critical mass of people in a given population gets infected by the virus, they develop some immunity against it and thus stop being the vessels for further transmission of the disease.
      • It involves a lot of death and suffering.
      • There is also an element of uncertainty because nobody knows how long immunity against COVID-19 lasts in a person who has already had it.
    • Vaccine: 
      • Considering the negative impacts of herd immunity there is so much work going on across the world on a COVID-19 vaccine.

Source: https://indianexpress.com/article/explained/coronavirus-vaccine-human-trials-volunteers-covid-19-pendemic-6414841/