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Currently submitted to: Journal of Medical Internet Research

Date Submitted: Aug 17, 2020

Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.

Searching PubMed during the COVID-19 pandemic

  • Jeffrey V Lazarus; 
  • Adam Palayew; 
  • Lauge Neimann Rasmussen; 
  • Tue Helms Andersen; 
  • Joseph Nicholson; 
  • Ole Norgaard



The ability to efficiently search the scientific literature is crucial during a pandemic.


To measure the performance of different searches in PubMed.


We tested PubMed searches for COVID-19 to identify which search strategy performed best according to standard metrics. We evaluated the performance of eight different searches in PubMed during the first ten weeks of the COVID-19 pandemic to investigate how complex a search string is needed. We also tested omitting hyphens and space characters as well as applying quotation marks.


The two most comprehensive search strings performed best, but the single-term search, COVID-19, performed well in terms of sensitivity (98.4/98.7 vs 94.4), positive predictive value (94.6/92.7 vs 95.3), and F-score (96.5/95.7 vs 94.8). We found that deleting a hyphen or space character could omit a substantial number of records. If entered correctly, a single-term search performed well although the number of relevant records would be increased by using a comprehensive search.


Expert search terms performed better than single term searches in PubMed, but not by a large margin. For day to day searches single term searches are probably fine whereas for systematic reviews more comprehensive searches should be used.


Please cite as:

Lazarus JV, Palayew A, Rasmussen LN, Andersen TH, Nicholson J, Norgaard O

Searching PubMed during the COVID-19 pandemic

JMIR Preprints. 17/08/2020:23449

DOI: 10.2196/preprints.23449


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