The National Library of Medicine (NLM) launched a pilot project in 2020 to test the viability of making preprints reporting COVID-19 research supported by NIH available via PubMed Central (PMC). As of March 2024, all preprints resulting from NIH-funded research are in PMC.
A preprint is a version of a scholarly or scientific paper that precedes formal peer review. Due to the rapidly evolving literature about COVID-19, preprints may be a valuable resource.