From the journal Science | By Jon Cohen

As desperately as the world wants a shot that provides protection from the new coronavirus afflicting one country after another, proving that a vaccine works safely can be painfully slow. Clinical trials start with small numbers of people and at first only look for side effects and immune responses, slowly building up to a large study that tests efficacy—a process that will take at least 1 year for the new virus. But as the scale of the pandemic becomes clearer, a provocative, ethically complicated proposal to shave many months off that timeline is gaining traction: Give people an experimental vaccine and then deliberately try to infect them.

Stanley Plotkin of the University of Pennsylvania, inventor of the current rubella vaccine and a leader in the vaccine field, says a carefully designed “human challenge” trial could offer clear proof of a vaccine’s worth at blinding speed. “We’re talking 2, 3 months,” says Plotkin, who has co-authored a commentary, now being submitted for publication, that describes how this might be ethically done. “People who are faced with a terrifying problem like this one will opt for measures that are unusual. And we have to constantly rethink our biases.” A similar proposal for coronavirus challenge studies was published online today in the Journal of Infectious Diseases.

Human challenge studies have been done for 2 centuries, and some continue today for influenza, dengue, cholera, and other infectious diseases. But as far back as the first vaccine in 1796, when Edward Jenner proved that giving cowpox to an 8-year-old boy protected him from injections with the deadly smallpox virus, the approach has raised concerns. Today, such trials have careful study designs and undergo extensive ethical reviews.

Yet even researchers who now conduct them argue against human challenges for the new coronavirus. Matthew Memoli, an immunologist at the U.S. National Institute of Allergy and Infectious Diseases who stages human challenge studies of influenza, notes that COVID-19 is so new it is not clear how often the virus makes people seriously ill or leaves them with long term complications. “Where you’re going to give somebody a virus on purpose, you really want to understand the disease so that you know that what you’re doing is a reasonable risk,” Memoli says...

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