The Case for Challenge Trials.


Research ethics committees and policymakers should permit and encourage Covid-19 challenge trials for new potential vaccines and variations on the administration of existing vaccines. In a challenge trial, researchers deliberately expose participants to a virus in order to test vaccines or treatments. This differs from standard trial designs for vaccines, where researchers enroll people in a trial, vaccinate some of them, and wait for the participants to naturally acquire a disease in order to test the effectiveness of the vaccine. Researchers have proposed and used challenge trials in the past, for example to test the effectiveness of vaccines and treatments for influenza or Respiratory Syncytial Virus (RSV). In the UK, public officials recently partnered with researchers to begin Covid-19 challenge trials to test new vaccines and to answer other questions about the virus. Other countries should follow their lead.

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