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 Table of Contents  
Year : 2021  |  Volume : 65  |  Issue : 4  |  Page : 375-379  

Top 100 cited articles in one year of COVID-19 research – A bibliometric analysis

1 Senior Resident, Department of Psychiatry, All India Institute of Medical Sciences, New Delhi, India
2 Senior Resident, Department of Ophthalmology, All India Institute of Medical Sciences, New Delhi, India
3 Senior Resident, Department of Anesthesiology and Critical Care, All India Institute of Medical Sciences, New Delhi, India
4 Junior Resident, Department of Ophthalmology, All India Institute of Medical Sciences, New Delhi, India
5 Associate Professor, Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
6 Assistant Professor, Department of Nephrology, All India Institute of Medical Sciences, New Delhi, India

Date of Submission04-May-2021
Date of Decision16-Sep-2021
Date of Acceptance24-Oct-2021
Date of Web Publication29-Dec-2021

Correspondence Address:
Arunkumar Subbiah
Department of Nephrology, All India Institute of Medical Sciences, New Delhi - 110 029
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijph.ijph_1133_21

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Background: Coronavirus disease (COVID-19)-related scientific publications have increased exponentially during the present pandemic but their influence on biomedical literature is not known. The characteristics of highly cited articles help us to identify important advances and their scientific impact. Objectives: In the present study, we have identified and analyzed the top 100 most highly-cited articles of COVID-19 research published in the year 2020. Methods: A cross-sectional bibliometric analysis was using the search terms “severe acute respiratory syndrome-coronavirus-2,” “COVID,” “nCoV,” “Coronavirus,” and “HCoV” querying the Google Scholar database using the program “Publish or Perish.” The first 100 English language articles with the maximum number of citations were identified and evaluated in detail. Results: The top 100 COVID-19 articles in 2020 had citations ranging from 1147 to 20,440. The median (interquartile range [IQR]) number of citations was 1970 (1456–2939). The number of authors ranged from 1 to 79 (median 10; IQR 5.25–19). The majority of first authors was from China (58%), followed by the United States of America (16%) and the United Kingdom (7%). The top three journals in terms of the number of published articles (37%) were the New England Journal of Medicine, Journal of the American Medical Association, and The Lancet. Most of the top-cited COVID-19 literature were descriptive studies focusing on epidemiology (48%) and clinical course (60%) of COVID-19. Conclusion: Clinical course and epidemiology have been the predominant areas of research interest in COVID-19 in 2020. Citation analysis of COVID-19 literature helps us to map out the most important focus for research in this pandemic and to identify gaps in knowledge which would guide further research.

Keywords: Bibliometric analysis, coronavirus, COVID-19, severe acute respiratory syndrome coronavirus-2

How to cite this article:
Ganesh R, Mahalingam K, Kandaswamy N, Shanmugam C, Vishnu VY, Subbiah A. Top 100 cited articles in one year of COVID-19 research – A bibliometric analysis. Indian J Public Health 2021;65:375-9

How to cite this URL:
Ganesh R, Mahalingam K, Kandaswamy N, Shanmugam C, Vishnu VY, Subbiah A. Top 100 cited articles in one year of COVID-19 research – A bibliometric analysis. Indian J Public Health [serial online] 2021 [cited 2022 Jul 4];65:375-9. Available from:

   Introduction Top

Coronavirus disease (COVID-19) caused by the 2019 novel coronavirus (2019-nCoV) has spread rapidly throughout the world. The new coronavirus (CoV) also called severe acute respiratory syndrome CoV-2 (SARS-CoV-2) belongs to β-CoV, which is similar to SARS-CoV and middle east respiratory syndrome CoV cause severe respiratory tract infection.[1] COVID-19 was declared as a pandemic by the World Health Organization (WHO) on March 11, 2020. The lack of knowledge coupled with the need to generate information led to an exponential increase in the number of publications in this field.

Though first reported in 1931, research on CoV gained momentum after isolation from humans in 1965.[2] Bibliometric analysis of CoV articles, published in the period between 1970 and 2019 found that the greatest number of CoV research works were contributed by the United States and were confined to virology journals.[3] However, this has changed during the current COVID-19 pandemic. The government's interest in generating evidence, increased funding for research and biomedical journals actively calling for articles on COVID-19 have shifted the attraction of the researchers toward COVID-19 research. The COVID-19 pandemic has caused significant morbidity and mortality on a global scale, utilizing vast amount of resources. Any information on the influence of research in COVID-19 is bound to help clinicians and researchers in evolving strategies for better management of this pandemic.

Highly cited articles in various fields assist in understanding the prominent areas of research and also points to future directions for research in the respective fields as seen in neurosurgery,[4] psychiatry[5] and radiology,[6] and others. A focussed bibliometric analysis of COVID-19 publications would reveal the influence of individual articles on the scientific community. It would also identify the various lacunae which need to be addressed in future research projects. This can also be used to gauge the academic excellence of the journals, institutes, and authors in COVID-19 research.

Prior bibliometric analyses in COVID have been restricted to a geographical locality or have been conducted early in the disease course which would not reflect the true impact of COVID research in 2020.[7],[8] In the present study, we aimed to identify and analyze the top 100 highly-cited articles in COVID-19 literature in the year 2020 which would provide a wholesome review of the topics and articles of interest throughout the entire year.

   Materials and Methods Top

All the articles on COVID-19 were searched on December 31, 2020, using Harzing's Publish or Perish version 7 on Windows, which is free and publically accessible software.[9] Academic citation data from various sources including Google Scholar, Scopus, Crossref, Microsoft Academic, and Web of Science can be accessed using Publish or Perish software. We used Google Scholar for retrieving the source data because of its scientific acceptance, easy accessibility, and wider scope. Apart from published articles, Google Scholar captures citation records from conference presentations, books, and other academic sources making it more comprehensive. We used the keywords “SARS-CoV-2,” “COVID,” “nCoV,” “CoV,” and “HCoV” in the Google Scholar database of Publish or Perish. A combination of these terms using the Boolean operators “AND” and “OR” were also used to ensure that all publications were adequately screened. Among the English language articles on COVID-19, the top 100 articles based on the number of citations were identified and analyzed in this study [Figure 1]. All the articles were downloaded and evaluated in detail for the title, authors, country of origin, institution, and month of publication. The country of the first author was considered the country of origin.
Figure 1: Flow diagram showing selection of articles.

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We also reviewed the important fields in COVID-19 research by evaluating the study content. Based on the literature on the focus of the COVID-19 articles,[10] we categorized the articles into various subfields – public health/epidemiology, clinical features/clinical course, diagnosis, management, prophylaxis, basic science, health care worker related, vaccine and psychological impact of COVID-19.

Descriptive analysis of the data was performed using IBM SPSS Statistics for Windows, version 23.0 (IBM Corp., Armonk, N.Y., USA).

   Results Top

All the terms listed under methodology were searched in the Google Scholar database using freely available “Publish or Perish” software. The top most-cited 100 articles were included in this study and analyzed. One of these top-cited articles was in the Chinese language and was excluded from our analysis.

The total number of citations ranged from 1147 to 20,440. The median (interquartile range [IQR]) number of citations for the articles included in the current study was 1970 (1456–2939). The article with the greatest citation count (n = 20,440) was “Clinical features of patients infected with 2019-nCoV in Wuhan, China” by Huang et al., 2020. The top 100 cited articles are enlisted in the [Supplementary Table 1]. The majority of the citation classics articles of 2020 were published in March (40.0%) followed by February (25%), January (16%), April (11%), May (7%), and October (1%).

Authors, country, and institutions

The number of authors ranged from one to 79 with a mean (standard deviation) of 14.66 (13.86) and a median (IQR) of 10 (5.25–19). The majority of studies were from China (58%), followed by the United States of America (16%), United Kingdom (7%), Italy (4%), Germany (4%), the Netherlands (2%), and Singapore (2%). Switzerland, Canada, France, Taiwan, and Japan contributed one article each to the top 100 most cited publications in 2020. There was one article from India and one report by the WHO in the top 100 most cited articles.

The institution with the most number of publications was Tongji Medical College (10%). Other institutions with maximum contribution were Zhongnan Hospital of Wuhan University (4%) and Guangzhou Medical University (3%). The University of Washington, Chinese Center for Disease Control and Prevention, Imperial College London, Johns Hopkins University, Leiden University Medical Center, National Centre for Infectious Diseases, Renmin Hospital of Wuhan University, and Zhejiang University School of Medicine contributed two articles each.

Journals and publishers

The top three journals in terms of the number of published articles (37%) were the New England Journal of Medicine (NEJM), The Journal of the American Medical Association (JAMA), and The Lancet. The complete list of journals with the most cited publications is listed in [Table 1]. The top six publishers of the citation classics articles were Elsevier (29%), American Medical Association (16%), Mass Medical Society (13%), Nature (9%), Radiological Society of North America (3%), and Springer (6%).
Table 1: List of Journals with most cited corona virus disease-2019 publications (n=100)

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Publication type and study design

The most cited publications were the original articles (65%). The distribution of the study design for the other top-cited articles is given in [Table 2].
Table 2: Study design of the top-cited articles on corona virus disease-2019 (n=100)

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Research focus

The focus of the top-cited articles was assessed to understand the relative importance of each research topic. Public health/epidemiology (48%), clinical features/clinical course (60%) were the most common areas of research focus among the most cited articles [Table 3].
Table 3: Research focus of the top cited articles on corona virus disease-2019 (n=100)

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   Discussion Top

The COVID-19 pandemic has created a significant impact on the existing health system and impelled the scientific community to increase the research related to COVID-19. However, with the enormous number of publications, it is essential to identify the important works which have generated interest and maximum knowledge in the field of COVID-19 research. The influence of a particular work in biomedical literature is assessed by the citations received by the publication. Citations received by an article though limited are the only available quantifiable measure of scientific reach of the article. Hence, when properly done, citation analysis gives us an idea about the scientific validation of every article. There are bibliometric analyses conducted earlier in COVID-19 literature.[11],[12],[13] However, most of these studies included articles till May 2020. In our analysis, we identified the top 100 most-cited articles for the complete year (2020) and also evaluated the contributions from various authors, institutions, countries, and journals to citation classics in the COVID-19 literature which had not been done earlier.

The top 100 articles were cited more than 1000 times with in the 1st year of publication. Our analysis showed that almost half of the citation classics in COVID-19 literature were descriptive studies focusing on epidemiology and the clinical course of COVID-19, followed by studies focusing on diagnosis and management of COVID-19. ElHawary H et al. also reported that the majority of the top 50 cited papers on COVID-19 assessed its clinical presentation and disease description.[14] This is understandable as the initial knowledge about the disease manifestations was grossly limited. Epidemiology and clinical course decide the health policy for managing an infectious disease and COVID-19 is not an exception. With progressive improvement in our understanding of the disease, the focus of future research is bound to shift to management and prevention (vaccine related)-based articles. The most cited article in our study was on the clinical features of patients infected with 2019-nCoV in Wuhan, China.[15]

More than half of the top 100 most cited articles in COVID-19 literature were original studies (65%) done on population with retrospective, prospective, ambispective, and cross-sectional study designs, and modeling studies and in vivo studies. With regard to the type of publication, the original studies were published as original articles, brief communications, rapid communications, and research letters. Earlier studies reported that the majority of maximum cited articles were commentaries and correspondence.[12],[14] This difference can be explained by their earlier timing of publication as prior publications were before definitive studies involving study patients could be done.

The wide variety in the type of publication could be due to various factors such as the increased number of articles submitted to the journals, the researcher's interest to publish in high-impact journals, and the journal's limitation in the total number of publications per edition. However, unlike in earlier cases where only the original articles were well cited, during the COVID era, good research published in all forms were well accepted. The type of publication did not hinder the impact of the research. Compared to the previous studies on COVID-19 bibliometric analysis, which reported that articles with maximum citations were case series published as commentaries or correspondences,[12],[14] the present study showed original studies published as original articles also had maximum citations. This shows a progressive improvement in the grade of evidence in COVID-19 scientific research.

Top-cited articles across different specialties have been used to find significant and emerging trends in the field. The citation figures seen in COVID-19 are usually attained after decades in other fields[4],[5],[6] but in COVID-19 literature the figures were reached within months which highlights the magnitude of COVID-19 worldwide. Major academic journals and institutions were committed to making COVID-19-related research data easily accessible. Most peer-reviewed research publications were made open access, research findings were made available via preprint servers before journal publication, and also shared immediately with the WHO. Scientific articles from journals such as Lancet were translated into Chinese and widely disseminated to the public in China and vice versa.[16] This increased the reach of scientific articles and made good research available worldwide.

Around 37% of articles included in the study were published in three of the top five biomedical journals namely, NEJM, JAMA, and The Lancet. Earlier studies on COVID-19 also showed that “The Lancet” and “NEJM” were journals with the maximum number of citations for articles on COVID-19.[13],[14] This can be attributed to the journal's scientific reach as seen by their impact factor and the preference of authors. The top ten journals contributing to citation classics included two multidisciplinary scientific journals, three general medical journals, three infectious diseases journals, one radiology, and one intensive care journal. The findings are similar to the earlier studies which showed that general medicine and infectious disease journals had maximum citations.[12] In the past 50 years, SARS-CoV-2 articles were published predominantly in virology journals. However, after the COVID-19 pandemic, SARS-CoV-2 research has gained attention from major biomedical journals. These trends implicate that the focus of major biomedical journals on infectious disease and health care policy will increase in the time to come. Although the field of interest and focus vary among journals, the interest to learn more about COVID-19 among researchers, healthcare providers and the public coupled with the paucity of non-COVID research propelled this trend of publication.

The majority of the studies were understandably from China. As the initial spread of the virus was first documented in China, researchers rushed to understand the nature of the virus and its clinical course. Chinese researchers published numerous research papers in both Chinese and English-language journals. Tongji Medical College of the Huazhong University of Science in Wuhan contributed the maximum number of most cited articles. The other major contributor is the United States, which otherwise also is the topmost contributor of research articles worldwide. Previous studies also showed similar findings.[12],[13],[14] Most of the multinational collaborative studies also had authors from China and the United States owing to their exposure to COVID-19 and expertise in conducting research studies.

One of the new trends emerging during the pandemic is the process of postpublication review. Several COVID-19 articles were corrected and retracted due to critical scrutiny by scholars and researchers. Among the citation classics, the article titled “On the origin and continuing evolution of SARS-CoV-2”[17] was corrected after publication. The article titled “Hydroxychloroquine and azithromycin as a treatment of COVID-19: results of an open-label nonrandomized clinical trial”[18] received an expression of concern. In 2020, almost 75 articles were retracted after publication due to concerns or errors in data and results.[19] The reason for these retractions was the rush to publish COVID-19 related articles by both the authors and editors. This can be avoided by following the standard peer-review process rather than expediting publications. With our understanding of COVID-19 evolving, many studies in COVID-19 research have contradicted the previous studies. This happens due to limited literature in the initial period of this pandemic.

Strengths and limitations

In this citation analysis to study the publication patterns of COVID-19 research, we have ensured a thorough search using a comprehensive set of search terminologies. However, citation analysis by no way helps us to ensure the scientific validity of the article and this is an inherent disadvantage of using citations to gauge the utility of scientific articles. Though we have included only English language articles for analysis, we had only one Chinese language article in the top-cited list. Considering the rapidly evolving nature of the pandemic and multiple publications on COVID-19, the citation count is bound to change frequently over time. Nevertheless, the characteristics of the top-cited articles would remain the same.

   Conclusion Top

The present pandemic has made COVID-19 the center of attention in medical research. The immediate and vital need for information on COVID-19 has increased the speed of the publication of articles. Most of the COVID-19 articles have been shared widely in academia and social media, leading to increase in the number of citations and altimetric values of the articles. The current bibliometric analysis highlights the most relevant articles on COVID-19 that have created maximum interest among researchers and healthcare professionals. As our understanding of SARS-CoV-2 tends to evolve, this study shows that peer-reviewed publications have provided the requisite knowledge to guide our management and this will channel our research interests in the time to come.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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  [Table 1], [Table 2], [Table 3]


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