Global trends in poliomyelitis research over the past 20 years: A bibliometric analysis

ABSTRACT

Poliomyelitis is an acute infectious disease caused by poliovirus. This bibliometric analysis aims to examine the status of poliomyelitis research in the past 20 years. Information regarding polio research was obtained from the Web of Science Core Collection database. CiteSpace, VOSviewer, and Excel were used to perform visual and bibliometric analysis with respect to countries/regions, institutions, authors, journals and keywords. A total of 5,335 publications on poliomyelitis were published from 2002 to 2021. The USA was the county with the majority of publications. Additionally, the most productive institution was the Centers for Disease Control and Prevention. Sutter, RW produced the most papers and had the most co-citations. Vaccine was the journal with the most polio-related publications and citations. The most common keywords were mainly about polio immunology research (“polio,” “immunization,” “children,” “eradication” and “vaccine”). Our study is helpful for identifying research hotspots and providing direction for future research on poliomyelitis.

KEYWORDS:

• Poliomyelitis
• vaccine
• acute flaccid myelitis
• bibliometrics
• Web of Science

Introduction

Poliomyelitis is a serious infectious disease caused by poliovirus that adversely affects the health of children. Poliovirus is a neurotropic virus that mainly infects the motor neurons of the central nervous system.¹ The majority of patients are 1 ~ 6 years old, and the main symptoms are fever, general discomfort, severe limb pain, irregular distribution and flaccid paralysis.² Importantly, poliomyelitis can lead to permanent paralysis, disability or limb deformities.³ With the promotion of live attenuated oral poliomyelitis vaccine (OPV), the global poliomyelitis eradication campaign has made remarkable achievements.^4,5 However, it is estimated that 4.7 per million births are affected by vaccine-associated paralytic poliomyelitis (VAPP) caused by OPV worldwide.⁶ Moreover, the live vaccine virus can mutate to regain the transmissibility and neurotoxicity ability of wild polioviruses (WPVs), leading to poliomyelitis outbreaks caused by circulating vaccine derived polioviruses (cVDPVs).⁵ Therefore, it is important to perform a quantitative analysis of the current research field, research hotspots, and prospects for future research on poliomyelitis.

Bibliometrics employs the combination of mathematics and statistics to analyze some of the characteristics of the literature.⁷ It is an important branch of information discipline system, and is also a discipline that reveals the law of literature information and science of documental information management.^8,9 By quantitatively analyzing the literature and understanding the development of this field, we can determine the law of scientific activities and use various bibliometric indicators to provide guidance for future effective scientific research activities.¹⁰ Therefore, we aimed to conduct an in-depth study of poliomyelitis research to evaluate the current research field, research hotspots, and development trends.

Methods

Data collection

In this study, the Web of Science Core Collection (WoSCC) database was used to search for publications.¹¹ To avoid bias caused by database updates, the paper search was completed in September, 2022. The search formula was [TS = (“poliomyelitis” OR “polio” OR “infantile paralysis”)] AND [Publication type = (Article) OR (Review)] AND [Language = (English)], and the publication year was limited to 2002–2021.

Data analysis

CiteSpace 6.1.R3, VOSviewer 1.6.18, and Microsoft Excel 2019 were used for bibliometric analysis and visualization.^12,13 CiteSpace was used to analyze the co-occurrence of countries and institutions, dual maps of journals, reference timeline, keyword timeline, reference bursts and keyword bursts.¹⁴ VOSviewer was used for co-citation and co-occurrence analysis, and to construct and visualize the literature network map.¹⁵ Excel software was used to analyze the annual publications.¹⁶ The H index was used to evaluate a researcher’s scientific contribution,^17–19 whereas the Journal Citation Reports (JCR) division of journals was utilized for the assessment of journals. Indicators for bibliographic material include the number of papers (Np) and the cited frequency (Cf).²⁰

Results and discussion

A total of 21,038 authors from 5,359 institutions in 168 countries published 5,335 poliomyelitis articles in 1,411 scientific journals from 2002 to 2021, based on the WoSCC database. With almost triple the number of articles published in 2021 compared to 2002, poliomyelitis research has grown steadily over the past two decades. The growing trend in publications shows that poliomyelitis is attracting increasing attention and interest.

Annual growth trend

A total of 5335 poliomyelitis -related papers retrieved from the WoS database were analyzed. As shown in Figure 1, the number of poliomyelitis-related papers has fluctuated over the past 20 years, with an overall increasing trend.

Figure 1. Trends of poliomyelitis-related publications over the past 20 years.

Analysis of the contribution of countries/regions

Supplementary Table S1 shows the top 10 countries/regions in terms of productivity of poliomyelitis -related papers. The USA published the most articles (n = 1,997), followed by England (n = 537) and Switzerland (n = 419). Interestingly, the top 3 countries in terms of Np also ranked in the top 3 in terms of Cf and H-index. USA had the highest Cf (n = 56,677) and H-index (105), followed by the UK and Switzerland. In addition, there is a small difference in productivity between the following countries: China, Sweden, Canada, and Australia. However, these countries are far from the USA. Among them, the Np in the USA is nearly 20 times higher than that in Australia. In addition, the Cf and H-indeces are also much higher in the USA, indicating that this country is the global leader in poliomyelitis research.

Contributions of institutions to global publications

Supplementary Table S2 lists the top 10 most common institutions listed in poliomyelitis research. The Centers for Disease Control and Prevention (CDC) (n = 528) has the highest Np. The World Health Organization (WHO) (n = 511) is next, followed by the University of London (n = 177). The CDC and WHO are the main contributors to poliomyelitis -related papers, and their total output is more than 10 times that of Johns Hopkins Bloomberg School of Public Health. The Cf (17,121) and H-index (63) of the CDC ranked first, indicating that this institution has good academic ability. The prevention and control of infectious diseases is the main work of the CDC, and its role is to detect and respond to emerging health threats and solve the biggest health problems that cause death and disability among Americans.²¹ Four of the top ten institutions are located in the USA. Our results indicated that more institutions in the USA are conducting research on poliomyelitis.

Analysis of authors

Supplementary Table S3 lists the 10 most prolific authors. These 10 authors published 694 articles, accounting for 13.02% of all articles. Sutter, RW (100) from the World Health Organization in Switzerland ranked first in poliomyelitis research, followed by Pallansch, MA (94) and Oberste, MS (91) from the Centers for Disease Control & Prevention in the USA. Therefore, to keep up with developments in this area, more attention and priority should be given to these authors. The Cf of RW’s Sutter was extremely high (3963), which indicated that his work had attracted attention from more scholars. The most frequently cited paper (n = 459) of Sutter, RW’s team proposes a strategy to eradicate poliomyelitis globally.²² In addition, they found that the low-dose monovalent type 2 oral poliovirus vaccine (mOPV2) had low immunogenicity, without a noninferiority margin of 10%.²³ They suggested that mOPV2 could serve as an economical measure to cope with the shortage of univalent poliomyelitis vaccines. Additionally, most of the top 10 authors were from the United States. The United States has a large number of excellent poliomyelitis researchers and attaches great importance to the field of poliomyelitis research.

Analysis of journals

A total of 1,411 journals published papers on poliomyelitis research. The top 10 journals published 1,273 papers, accounting for 23.87% of all publications (Supplementary Table S4). Vaccine published the most articles (n = 495), followed by Journal of Infectious Diseases (n = 201) and Plos One (n = 104). Additionally, the journals are ranked in the top 10 for the following reasons: first, the scientific directions and research topics covered by these journals are most relevant to the poliomyelitis topic, and scientists are easily encouraged to submit relevant research to these journals. Second, these journals are the most influential professional journals, helping researchers advance their scientific ideals and perspectives through discussions and interactions with their peers (improve their academic standards and research skills). Finally, these journals have relatively short peer review cycles, which makes them more popular with researchers.

The dual-map overlay of journals depicts the distribution of topics in scientific journals (Figure 2). Citing and cited journals are located on the left and right, respectively, with colored paths indicating citation relationships. Figure 2 shows the five primary citation paths for poliomyelitis. The strongest citation relationships were from Molecular/Biology/Immunology journals to Molecular/Biology/Genetics journals.

Figure 2. The dual-map overlay of journals on poliomyelitis. The citing journals are on the left, whereas the cited journals are on the right. The colored path represents the citation relationship. In the field of poliomyelitis, both the molecular/biology/immunology journals (orange lines) and medicine/medical/clinical journals (green lines) are significantly influenced by molecular/biology/genetics journals and health/nursing/medicine journals. The ellipse indicates the numeric ratio of the authors to publications: the horizontal length represents the number of authors, whereas the vertical length represents the number of publications.

Publication and co-cited references

Supplementary Table S5 shows the top 10 articles by total citations (9 reviews and 1 paper), which were mainly published between 2002 and 2015. They have summarized and analyzed the pathogenesis, diagnosis, treatment, and epidemiological virological features associated with poliomyelitis. Poliomyelitis vaccine research accounted for 50% (5/10) of the ten most cited articles, indicating that poliomyelitis vaccine research is a hot topic for most researchers.^22,24–27 In addition, there are two studies on enterovirus 71,^28,29 two articles on the treatment of poliomyelitis ^30,31 and one virological study on poliomyelitis.³²

Supplementary Figure S1A shows the 341 articles (publications with a minimum citation frequency of more than 30 times) with high citation frequency analyzed using VOSviewer. Different colored nodes represent different clusters. In addition, a larger area of the node represents a global influential article. Kew,OM et al.²² wrote an influential article in 2005, that described vaccine-derived polioviruses and the endgame strategy for global poliomyelitis eradication.

The evolution of research hotspots over time can be shown by the reference timeline view. The terms with the highest frequency in each cluster were identified as the cluster label. As shown in Supplementary Figure S1B, clusters #0 (vaccine-derived poliovirus), #2 (democratic republic), #5 (nile virus infection) and #6 (mouth disease) initiated earlier, while #1 (modeling poliovirus transmission), #3 (inactivated poliovirus vaccine), #4 (acute flaccid myelitis), #7 (all-cause mortality) and #8 (core group poliomyelitis project) were still under study in recent years. Timeline visualization of the references and keywords (Supplementary Figures S1B) showed that “vaccine” and “acute flaccid paralysis” were areas of common interest. OPV and IPV have contributed to the global eradication of poliomyelitis. A recent study on the poliomyelitis vaccine showed that IPV had stronger immunogenicity than OPV.³³ Moreover, acute flaccid paralysis is one of the common clinical manifestations of poliomyelitis, and is characterized by acute weakness and paralysis and decreased muscle tone.³⁴ IPV can prevent paralytic poliomyelitis for a long time. Therefore, research on vaccines and acute flaccid paralysis is of great significance.

The top 20 references with the most powerful citation bursts are shown in Supplementary Figure S2. Kew, O et al. ‘s publication has the highest strength (44.66). Their paper described a poliomyelitis outbreak in Hispaniola, which was associated with circulating type 1 vaccine-derived poliovirus.³⁵ In addition, the study conducted by Kew, OM et al. had a high burst strength.²² This is consistent with the results of the reference co-citation analysis in the previous section. Moreover, the number of citations of Hampton, LM’s articles has increased significantly in recent years. His research attracted attention from many scholars worldwide. He highlighted the importance of discontinuing the trivalent OPV and introducing an inactivated poliovirus vaccine (IPV), which is essential to achieving a poliomyelitis-free world.³⁶

Keyword analysis

We analyzed 354 keywords from the titles and abstracts of 5,335 publications using VOSviewer and CiteSpace (Supplementary Figures S3, S4). Cluster 1 (green) mainly showed immunological research on poliomyelitis, and cluster 2 (yellow) was mainly concerned with postpoliomyelitis syndrome. Cluster 3 (red) focused on epidemiological studies on poliomyelitis. Cluster 4 (purple) mainly focused on the study of the poliomyelitis eradication strategy. Cluster 5 (blue) primarily focused on vaccine research for poliomyelitis. The highly frequent occurrences of keywords were “poliomyelitis,” “immunization,” “children,” “eradication,” and “vaccine,” suggesting that poliomyelitis research was primarily concerned with immunology (Supplementary Figure S3A).

As shown in Supplementary Figure S3B obtained from VOSviewer, the color shades represent different mean publication years. Yellow keywords represent an average publication time later than blue keywords. Cluster 1 and Cluster 4 (more yellow nodes) indicated that poliomyelitis-related immunological and eradication strategy studies were hot topics in the field of poliomyelitis. Additionally, “immunogenicity,” “eradication,” “vaccination coverage,” “rehabilitation,” “acute flaccid paralysis” and “simian virus 40” have been the focus of researchers’ attention (Supplementary Figure S4A). Additionally, “acute flaccid myelitis,” “worldwide,” “open label,” “update,” “mortality,” “paralysis” and “vaccine hesitancy” were recent popular keywords in Supplementary Figure S4B. These findings indicated that researchers have recently devoted considerable attention to acute flaccid paralysis, vaccine research and epidemiological research related to poliomyelitis.

Advantages and disadvantages

Bibliometric analysis and literature visualization provide a better understanding of trends and key points in poliomyelitis research.³⁷ However, this study has some limitations. First, the studies from the SCI-expanded database only contained articles and reviews in English. Second, as VOSviewer and CiteSpace cannot analyze the full text of the publication, some information may be ignored. Finally, some recently published articles may be ignored due to their low citation frequency.³⁸

Conclusions

Although the number of poliomyelitis articles published fluctuated slightly over the past 20 years, the overall trend was increasing. The USA is most dominant country in this field and has considerable influence. Moreover, immunological research on poliomyelitis has attracted widespread attention, and IPV and acute flaccid paralysis have become potential hotspots in poliomyelitis research. Our study is helpful for identifying research hotspots and providing directions for future research on poliomyelitis.

Expert opinion

Due to the global poliomyelitis eradication campaign, there has been a significant reduction in the number of wild poliovirus cases worldwide. However, children are still at risk of being paralyzed by poliomyelitis until all polioviruses, including wild poliovirus and cVDPV, are eliminated globally. We should continue to strengthen the research on poliomyelitis to prevent the development of the epidemic. In the last 20 years, research on poliomyelitis has increased each year, but less attention has been given to research on poliomyelitis based on bibliometric analysis. Therefore, the focus of our study is to clarify and summarize the current situation, hotspots and development trends of polio-related research from different aspects based on bibliometric analysis. Our research has found some excellent and outstanding publications, countries, institutions, authors and journals, and we will obtain more valuable information by following them. In our opinion, research direction in this field, in the next few years, should focus on two main aspects. The first is the study of the poliomyelitis vaccine. At present, the main vaccine is still OPV, mainly because of its good immune effect, low price, and simple vaccination method, while IPV is expensive and the vaccination method is relatively complex. However, the latest research shows that IPV has higher safety and stronger immunogenicity. Therefore, we need to weigh the pros and cons of vaccines to formulate the best epidemic prevention strategy. The second is the study of acute flaccid paralysis, as the most common clinical manifestation of poliomyelitis, and the monitoring and treatment of acute flaccid paralysis patients play an important role in poliomyelitis. Therefore, the above two aspects of research will be of great significance to global poliomyelitis eradication.

Authors’ contributions

YZ decided and conceptualized this article, and revised the draft. ZL and QL wrote the manuscript. BH, YT and HBG collected and analyzed the data. ML, SP and MW prepared the figures and tables. YZ and JYL was the guarantor of the overall content. All authors approved the final version of the manuscript and agreed to be accountable for all specs of the work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary data

Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/21645515.2023.2173905.

Additional information

Funding

This study was supported by National Natural Science Foundation of China (82102581, 82270930), National Postdoctoral Science Foundation of China (2021M693562), Provincial Natural Science Foundation of Hunan (2019JJ40517, 2022JJ40843), Provincial Outstanding Postdoctoral Innovative Talents Program of Hunan (2021RC2020), Young Investigator Grant of Xiangya Hospital, Central South University (2020Q14), FuQing Postdoc Program of Xiangya Hospital, Central South University (176) and Fund of Reform and Practice of Ideological and Political in Xiangya Hospital, Central South University (36, 40).