We conducted a literature search on the Web of Science Core Collection (WoSCC) database (https://www.webofscience.com/wos/woscc/basic-search) on January 11th, 2024. The search formula was TS= ((RNA vaccine AND COVID-19) OR (RNA vaccine AND SARS-COV-2)), the published year was set before 2024, and the type of documents was set to articles and reviews. The language filter was set in English ( Figure 1 ). According to our search strategies, there were 2962 studies of RNA vaccines for COVID-19 between 2020 and 2023 (0 publication in 2019), including 1956 articles and 1006 reviews. The analyzed publications were written by 23141 authors (93 with single-authored documents and 23048 with multi-authored documents) from 104 countries and 908 journals.

Figure 2A shows that the number of annual related publications increased rapidly year by year from 2020 to 2022. In 2020, 271 articles were published, while 795 in 2021, 1144 in 2022, and 752 in 2023. The most productive year was 2022 (n = 1144) with the annual scientific growth rate of 143.9%. The total number of citations per article and the average citations per year have decreased ( Figure 2B ). In 2020, the average number of citations per article was 123.5, 45.9 in 2021, 17.3 in 2022, and 2.48 in 2023. The total average number of citations per year was 24.7 in 2020, 11.5 in 2021, 5.8 in 2022, and 1.2 in 2023.

We filtered and visualized 104 countries that published more than ten articles and constructed a collaborative network based on the number and relationship of publications in each country. From Figure 3A , we can point out that the United States has the highest literature output(n=4163) on COVID-19 RNA vaccines, and the number is significantly higher than that of China(n=1844) and Italy(n=936). Notably, there is much active cooperation between different countries. For example, the United States closely cooperates with China, the United Kingdom, Germany, and Italy; India actively cooperates with Saudi Arabia ( Figure 3B ). It shows that the United States has the most significant number of SCPs and MCPs, which indicates that the United States has the most researches on COVID-19 RNA vaccines and cooperation with other countries in this regard, followed by China on both SCP and MCP ( Figure 3C ).

In Figure 4A , Harvard University has the highest number of institutions that receive and publish articles (n=249), followed by the University of California System (n=160) and Harvard Medical School (n=76). Half the top 20 most relevant affiliations were from the United States, followed by the United Kingdom, China, France, and Israel. Subsequently, we selected 34 institutions based on visualization with a minimum number of publications equal to 5. We constructed a collaborative network based on the number of publications and relationships of each affiliation ( Figure 4B ). As shown in Figure 4B , Harvard University and Harvard Medical School cooperated the most, and Tel Aviv University and Sheba Medical Center also had active cooperation. In addition, we noticed that Harvard University had published the most papers and collaborated with the most significant number of affiliations.

The number of academic publications by an author can represent research activities and contributions in the field to some extent. As shown in Table 1 , Ugur Sahin was the most influential author from University Medical Center, Johannes Gutenberg University, between 2020 and 2023 on COVID-19 RNA vaccines, who had published 14 articles in this field, whose h-index is 9, g-index is 14, m-index is 2.6. He also has the highest number of total citations(n=14203). Pei-Yong Shi’s h-index(n=12) is a close second. Pei-Yong Shi published 16 articles in this field between 2020 and 2023; his g-index is 16, and his m-index is 2.4. Notably, we can find that Pei-Yong Shi and Ugur Sahin had the most significant academic influence on COVID-19 RNA vaccines.

Followed by Frontiers in Immunology (n=105, 3.54%) and Viruses-Basel (n = 58, 2.94%), the Vaccines published the most articles on COVID-19 RNA vaccines (n =171, 5.77%) throughout four years. However, the New England Journal of Medicine, Nature, and Science were the most cited journals. Bradford’s law was applied to assess the core journals in the field of COVID-19 RNA vaccines. As shown in Figure 5A , the core journals in COVID-19 RNA vaccines were Vaccines, Frontiers in Immunology, Viruses-Basel, Clinical Infectious Diseases, Journal of Medical Virology, etc. As for co-cited journals in Figure 5B , journals were categorized into different clusters. The nodes with different colors in the graph represent different clusters. The node size represents the number of articles published in the journal, and the thickness of the lines represents the number of connections between nodes. Frontiers in Immunology, Vaccines, and Journal of Medical Virology were the top three most influential journals in this field. This result can help scholars to select the best-fit journals for submitting their research findings. Also, Table 2 lists the top 20 most-cited publications on COVID-19 RNA vaccines. All these productions were published between 2020 and 2023, and 65% obtained more than 1000 citations. Table 2 shows that the New England Journal of Medicine was the highest-cited journal with the highest h-index, m-index, and total citations. Frontiers in Immunology has the highest g-index. These indexes showed the importance of these two journals on COVID-19 RNA vaccines.

The relations between journals, authors, and affiliations were visualized using the three-field plot (TFP). In this instance, the significant features were represented in the diagram by rectangles with different colors. The height of the rectangles in the diagram of the TFP depended on the rate or value of the summation of the relations arising between the component the rectangle represents (journals, authors, and affiliations) and the diagram of other elements. The more relations the component or element had, the higher the rectangle represented. Figure 6 shows the TFP analysis of publications on COVID-19 RNA vaccines centered on relations between the journals, authors, and affiliations. The diagram demonstrated the top journals, authors, and affiliations relations in publications on COVID-19 RNA vaccines and their related studies during these four years.

The top 20 most cited articles were published in 11 journals between 2020 and 2023 ( Table 3 ). Seven articles were published in The New England Journal of Medicine, and four were published in Nature. With 8609 citations, the top-cited article was published by Fernando P Polack from the New England Journal of Medicine in 2020. The total citations per year were 1721.80, and the normalized total citation was 69.69. The following one was published by Edward E Walsh and received 1574 citations, whose total citations per year was 314.80, and the normalized total citation was 12.74.

There are 50 references of co-citation with more than five citations. As shown in Figure 7 , Wrapp d 2020 (34) has the highest number of connections with other references, followed by Hoffmann m 2020 (35). Polack fp 2020 (24) has the highest value of PageRank to get other references, which shows the importance of a node to get other nodes, followed by Baden lr 2021 (36).

Keywords are always the core research content highly condensed and summarized by researchers, which can reflect the central theme of the research. Therefore, keyword co-occurrence analysis is a crucial way to determine the main research direction and hot research topics of a specific discipline. Among Figure 8B , the most frequent author’s keywords were “covid-19” (n =1166,25%), “sars-cov-2” (n=1054,22%), “vaccine” (n=323,7%), “coronavirus” (n =183,4%), “vaccines” (n =174,4%), and “vaccination” (n = 170,4%). The overall keyword network visualization is presented in Figure 8 . It can be seen that the frequency of the words COVID-19 and SARS-COV-2 has significantly increased from 2020 to 2023.

Firstly, to ensure high-quality bibliometric analysis, the analysis of this study is based on articles in the Web of Science database, one of the most commonly used scientific publication databases. However, some studies may be omitted as they are published in non-SCI journals or other databases. Secondly, bibliometric analyses cannot completely replace system retrieval. Third, metrology cannot evaluate the quality of a single study because the citation index is time-dependent, meaning that recent articles may be less cited than earlier, even if they are more valuable. These limitations may slightly impact the overall results but are unlikely to alter the main trends presented in this article. In general, our research has provided a basis for understanding the research topics of the COVID-19 RNA vaccines and the production and application of the RNA vaccine.

In this study, research articles on RNA vaccines for COVID-19 published between 2020 and 2023 as original articles or reviews in English were considered eligible. Web of Science core collection database was used.

In the advanced search option of the Web of Science database, using an appropriate combination of Boolean and wildcard search operators, the following keywords were searched: “Corona Virus Disease 2019”, “COVID-19”, “RNA”, and “vaccines”. The search was performed on January 11th, 2024, and the entire search strategy is presented in TS = ((RNA vaccine AND COVID-19) OR (RNA vaccine AND SARS-COV-2, the type of documents is set to “articles” and “reviews”. The language of articles is set as English only. Then, all the resulted information, including full records and cited references, was downloaded in txt format.

Data management and bibliometric analyses were conducted using the Bibliometrix package (version 3.1.4) (57) and Biblioshiny (57) web apps under R (version 4.0.2). We retrieved all the main information and features included in the study. Publications and citation trends were constructed over four years. From 2020 to 2023, the most influential countries on COVID-19 RNA vaccine research were retrieved and presented as a cluster collaboration network. The cooperative world map represents world research cooperation, with the minimum edge set at 10. In addition, we identified the most productive institutions based on the highest number of paper contributions to the topic over the past four years. We used leading eigenvalue clustering algorithms to construct a collaborative network between institutions with more than five citations. We determined the author with the highest contribution based on the highest number of papers and the top 20 co-citation networks of influential authors. The 20 most cited references and the most influential journals were also identified, and some characteristics were searched, such as h-index, g-index, m-index, the total number of citations, the number of papers on the subject published in the journal, and the year when the journal began to publish COVID-19 RNA vaccine-related topics. In order to observe the inflow and outflow of journals, authors, and affiliated institutions that have contributed to the COVID-19 RNA vaccines in the past four years, a three-field plot was constructed. A tree chart was prepared to display keywords published on this topic from 2020 to 2023.