Objectives: With over 100,000 (and counting) citations for “covid-19” in PubMed, the impact of the current pandemic on the biomedical literature is apparent to even the most casual reader. Less clear however is how that impact has changed over the course of the past year, or how it has varied between disciplines. This study seeks to quantify how the production of items relating to Covid-19 has changed over time by examining those citations in PubMed on a weekly basis.
Methods: Counts of items relating to Covid-19 in PubMed were determined by programmatically searching the string “Covid-19” in PubMed using Python programs to interface with NCBI’s public API. Searches were scoped by week using the “Create Date” PubMed field. In addition to raw numbers of Covid-19 items, further counts were taken of those Covid-19 items found in Journal Subsets, Publication Types and selected by the LitCovid filters.
Results: Overall production of Covid-19 items quickly rose to a level of 8,000 per 100,000 PubMed items in May of 2020 and have primarily remained in the range of 6,500 to 8,000 up to the present. For Journal Subsets, the most striking pattern was that seen in the percentage of Covid-19 items found in "Abridged Index Medicus". For this large and important subset, just over 20% of all items were about Covid-19 in May of 2020, but that percentage has fallen steadily in subsequent months. In terms of Publication Types, letters was the predominant type last May, but has since been overtaken by reviews. Finally, for LitCovid items, there was a notable decline in "Mechanism" items from the beginning of the pandemic, when they comprised over half of all items.
Conclusions: Much has changed over the past year in terms of our understanding of SARS-CoV-2 and Covid-19. In the face of this, the overall pattern of Covid-19 item production in PubMed holding steady seems somewhat paradoxical. It remains to be seen if this trend will hold as 2021 continues.