ut federal officials haven't yet decided the fate of a handful of studies on influenza and Middle East respiratory syndrome (MERS) that were put on hold in October 2014.

Two investigators whose controversial studies on deadly avian influenza viruses are among 11 on hold welcomed the end of the pause. "This NIH decision allows us to move forward," virologist Yoshihiro Kawaoka of the University of Wisconsin in Madison wrote in an email.

NIH officials believe the pending studies are probably outdated and scientists will want to submit new proposals. The new process, NIH Director Francis Collins says, "will help to facilitate the safe, secure, and responsible conduct of this type of research." Critics of the studies, meanwhile, are withholding judgment until they see how the review process plays out.

Concerns over so-called "gain-of-function" (GOF) studies that make pathogens more potent or likely to spread in people erupted in 2011, when Kawaoka's team and Ron Fouchier's lab at Erasmus Medical Center in Rotterdam, the Netherlands, announced that they had modified the H5N1 bird flu virus to enable it to spread between ferrets.