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Current Affairs

WHO approves COVID-19 trial that deliberately infects participants

Date: 18 May 2020 Tags: Miscellaneous

Issue

The World Health Organization has said that well-designed human challenge studies could not only accelerate coronavirus (COVID-19) vaccine development but also make it more likely that the vaccines ultimately deployed will be far more effective.

 

Background

In human challenge studies, healthy participants are first administered the candidate vaccine and then deliberately exposed to novel coronavirus. In conventional clinical trials, healthy participants are administered the candidate vaccine, and the safety and efficacy of the vaccine is assessed through natural infection.

 

Details

  • The guidelines say that it would be “substantially faster” to carry out vaccine field trials through human challenge studies as far fewer participants need to be exposed to candidate vaccines to provide (preliminary) estimates of efficacy and safety.

  • It says this approach will make it possible to compare the efficacy of multiple vaccine candidates and select the most promising vaccines for larger studies.

  • In addition to accelerating vaccine development, human challenge studies can help validate tests for immunity to the virus, identify correlates of immune protection, and investigate the risks of transmission by infected individuals.

  • While human challenge studies are ethically controversial, such studies have been performed safely in tens of thousands of people in the last 50 years and helped accelerate the development of vaccines against typhoid and cholera. Such a study for Zika virus was also conducted.

  • According to the guidelines, challenge studies would be least risky for young healthy adults aged 18-30 years, as the hospitalisation rates in this age group is about 1% and fatal infection rates around 0.03%. 

  • Human challenge studies are to be carried out only in specialised centres where close monitoring and ready access to early supportive treatment for participants, including critical care if required is available.

  • But what makes such studies for COVID-19 particularly risky and challenging is the fact that pathogenesis of the disease is poorly understood and there is no approved treatment available in case participants develop the disease.

  • Potential benefits and risks should be assessed, quantified and compared with other feasible study designs, and the expected benefits should be maximised and the risks minimised.