U.K. Plans ‘Challenge Trials,’ Which Will Intentionally Give People COVID-19 to Test Vaccines
On Oct. 20, researchers at the Imperial College of London announced plans for the first human challenge study of COVID-19, which involves deliberately infecting volunteers with the virus that causes the disease, in order to test the effectiveness of vaccines. The strategy is controversial, as researchers have to weigh the risks of infection against the benefits of learning how well the various vaccine candidates can fight that infection. The strongest argument in favor of the studies has to do with time. If cases of COVID-19 are waning, then the likelihood that people who are vaccinated would get exposed to and potentially infected with the virus naturally declines as well, and it takes researchers longer to accumulate enough data to tell if a vaccine is effective or not. By intentionally exposing people to the virus after they have been vaccinated, researchers can shrink this timeline significantly. Scientists have used the model to test vaccines against a number of different diseases, including the very first one against smallpox—Edward Jenner infected his son with cowpox, and then exposed his son to smallpox as a way to test his theory that exposure to the former would protect his son from infection by the latter. Scientists tested an H1N1 influenza vaccine by exposing people to the flu, and did the same with a cholera vaccine and the bacterium that causes it. But the strategy requires a solid base of information about both the disease and the vaccine in order to ju...
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