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Annual MEDLINE/PubMed Year-End Processing (YEP): Impact on Searching During Fall 2020

What is YEP? | Indexed Citations | In Process Citations | Searching | Other Resources

Indexed Citations

On December 2, 2020, NLM® expects to temporarily halt the addition of newly-indexed MEDLINE citations to PubMed. NLM indexing staff will continue to index citations, but these completed records will be held and not added to PubMed until the normal update schedule resumes. Once the end-of-year activities are complete (tentatively targeted for mid-December 2020), the normal MEDLINE/PubMed update schedule will resume, and PubMed will use 2021 vocabulary in the MeSH® translation tables and MeSH database, as well as in the citation data.

In Process Citations

During end-of-year activities, "in process" citations will continue to be added to PubMed. As a result, the number of PubMed records labeled [PubMed - in process] will temporarily increase.


A search limiting terms to fields affected by indexing (e.g., telemedicine [mh]) does not retrieve in process or publisher-supplied records. Therefore, during end-of-year activities when we are not adding recently completed, indexed citations to MEDLINE/PubMed, such searches - including those stored in My NCBI and retrieved through RSS feed stored searches - may not retrieve new records for some weeks. To retrieve new, in process records during this time, you should use searches that do not limit to affected fields (e.g., telemedicine). Note that the search terms are not tagged in this example. In early December, the in process citations that are within the scope of MEDLINE and that have been indexed since December 2, 2020 will be replaced as indexed citations with 2021 MeSH terms, Publication Types, etc. Searches, including My NCBI Stored Searches, containing tagged search terms will then retrieve all applicable MEDLINE records.

Other Resources


Important Dates

• December 2, 2020: NLM expects to temporarily halt the addition of fully-indexed MEDLINE citations to PubMed.

• Mid-December 2020: PubMed's MEDLINE citations, translation tables, and the MeSH database will have been updated to reflect 2020 MeSH.

NLM Technical Bulletin Articles

•Articles in the November-December issue that address changes to LocatorPlus and NLM Catalog, which may be different from MEDLINE.

Background information is available in previous NLM Technical Bulletin articles.

Related Articles

Skill Kit: The Effects of Year End Processing (YEP) on Saved Searches or RSS Feeds

Heading Mapped-to Maintenance: for Supplementary Concept Records' Names of Substance

Changes in the Treatment of Chemical Data in MEDLINE Citations

Pharmacologic Action Headings: PubMed

Last Reviewed: September 14, 2020