The US moratorium on gain-of-function experiments has been rescinded, but scientists are split over the benefits—and risks—of such studies. Talha Burki reports. On Dec 19, 2017, the US National Institutes of Health (NIH) announced that they would resume funding gain-of-function experiments involving influenza, Middle East respiratory syndrome coronavirus, and severe acute respiratory syndrome coronavirus. A moratorium had been in place since October, 2014. At the time, the NIH had stated that the moratorium “will be effective until a robust and broad deliberative process is completed that results in the adoption of a new US Government gain-of-function research policy”. This process...