Testing SARS-CoV-2 vaccine efficacy through deliberate natural viral exposure

Abstract

A vaccine trial with a standard challenge design can be faster than standard phase III once it starts, but it requires a long prior process, in part, to grow and standardize challenge virus in the laboratory. This detracts somewhat from its overall promise for accelerated efficacy testing of SARS-CoV-2 vaccine candidates, and from the ability of developing countries and small companies to conduct it. We describe a challenge design that avoids this part of the long prior process. The new design has additional ethical, scientific, and feasibility strengths, compared to standard challenge designs and to standard phase III designs, and should be considered for future vaccine trials.