Search strategy.

<div><p>Introduction</p><p>Journal self-citation contributes to the overall citation count of a journal and to some metrics like the impact factor. However, little is known about the extent of journal self-citations in COVID-19 research. This study aimed to determine the journal self-citations in COVID-19 research and to compare them according to the type of publication and publisher.</p><p>Methods</p><p>Data in COVID-19 research extracted from the Web of Science Core Collection 2020–2023 was collected and further analyzed with InCites. The journals with the highest self-citation rates and self-citation per publication were identified. Statistical comparisons were made according to the type of publication and publishers, as well as with other major infectious diseases.</p><p>Results</p><p>The median self-citation rate was 4.0% (IQR 0–11.7%), and the median journal self-citation rate was 5.9% (IQR 0–12.5%). 1,859 journals (13% of total coverage) had self-citation rates at or above 20%, meaning that more than one in five references are journal self-citations. There was a positive and statistically significant correlation of self-citations with the other indicators, including number of publications, citations, and self-citations per publication (p<0.001). Editorial materials contributed more to journal SC with a median self-citation rate of 5%, which was statistically higher than other documents such as articles, letters or reviews (p<0.001). Among the top twelve publishers, the Multidisciplinary Digital Publishing Institute had a median self-citation rate of 8.33% and was statistically higher than the rest (p<0.001). Self-citation rates for COVID-19 were lower than tuberculosis and HIV/AIDS, but self-citations per publication of these diseases were statistically lower than those for COVID-19 (p<0.001).</p><p>Conclusion</p><p>Some journals from the Web of Science Core Collection displayed exorbitant journal self-citation patterns during the period 2020–2023. Approximately, one in every five paper references in COVID-19 is a journal self-citation. Types of publication such as editorials engage in this practice more frequently than others, suggesting that in COVID-19 research, self-citing non-citable items could potentially contribute to inflate journal impact factors during the pandemic.</p></div>