And what scientists learned they still needed it for.

When papers from China began flooding the websites bioRxiv and medRxiv in the first months of 2020, it was a strange and notable change. Founded as places where scientists could post drafts of research papers before those papers went through a traditional peer review, these sites had never really advertised much in China or gotten many submissions from scientists in that country before, said Richard Sever, the co-founder of bioRxiv and medRxiv. The sudden shift turned out to be a preview of the pandemic to come. “We got a wave of submissions from China and then a wave of submissions from Italy. And I remember being with a colleague, looking at submission numbers, and the chart was so eerily familiar,” Sever said. “It looks just like the progression of pandemic caseloads.”

“Preprint,” or “prepress,” servers have been around for decades, but during the COVID-19 pandemic, they took on a new notoriety and level of importance. Two of these sites alone, bioRxiv and medRxiv, hosted 25 percent of all COVID-19-related scientific research published during the pandemic’s first 10 months — more than 10,000 papers. In contrast, only 78 preprints were uploaded to bioRxiv during the entire 2015-16 Zika epidemic. (The medRxiv site didn’t exist yet.) COVID-19 proved to scientists that preprint servers are crucial resources in a crisis. At the same time, though, experts said the pandemic also made the shortcomings of scientific publishing clear. Preprints share a lot of the same limitations as peer-reviewed research, especially when it comes to how the media and the public use research once it’s out in the world for all to see.

Websites that post scientific research before it has been peer-reviewed and published in a scientific journal have been active since at least 1991, when the classic arXiv site, originally used mainly by physicists, went live. Even before that, scientists have shared drafts and notes among themselves through personal correspondence ever since “science” as a field became a thing. Those lines of communication exist parallel to the traditional process of peer review, which puts gatekeepers between research and publication. First, a paper has to be accepted by the editors of a scientific journal. Then, it goes to a (usually anonymous) panel of other scientists for critique. Their notes will lead to edits, which usually lead to more experiments, and then (hopefully) eventual publication.