This scoping review will summarize COVID-19 vaccines research activities and describe the extent/breadth, range, and nature of evidence in research related to COVID-19 vaccines. The framework described by Arksey and O’Malley  and Joanna Briggs Institute (JBI)  methodological guidance has been followed to design this scoping review. The scoping review will involve five stages: 1) identifying the research question; 2) identifying relevant studies; 3) study selection; 4) charting the data; 5) collating, summarizing, and reporting results. The reporting of this protocol is based on the Preferred Reporting Items for Systematic Reviews and Meta Analyses protocols (PRISMA-P) checklist  (Additional file 1) and the full text will follow to Preferred Reporting Items for Systematic Reviews and Meta Analyses Extension for Scoping Reviews (PRISMA-ScR) guidelines . This protocol has not been registered, because the International Prospective Register of Systematic Reviews (PROSPERO) website does not currently accept scoping reviews. As there are some uncertainties at protocol stage, if there are any deviations from the following full-text, we will report them in detail, as well as the reasons. Meanwhile, given the outbreak and vaccines research are still ongoing, our research team will update the results every 2-3 months.
Stage 1: identifying the research question
Following Arksey and O’Malley’s approach and JBI methodological guidance , this scoping review begins by formulating our research questions, which will guide the following processes that include whole of the subsequent literature search and study selection. We will focus on the following questions:
The trends in publications of COVID-19 vaccines research (e.g., volume of publications, monthly distribution) and the bibliographic characteristics (e.g., journal, country, study type);
The available evidence in the COVID-19 vaccines’ literatures and the pivotal points that they focusing on;
The scientific quality of the critical evidence types (i.e., randomized controlled trials [RCTs], systematic reviews and meta-analyses) for COVID-19 vaccines, and if they adhering the best practices required by guidelines or tools (e.g., Consolidated Standards of Reporting Trials [CONSORT] , Preferred Reporting Items for Systematic Reviews and Meta Analyses[PRISMA] , A Measurement Tool to Assess Systematic Review 2 [AMSTAR 2]) ;
The knowledge gaps in COVID-19 vaccines research, and critical questions that should be focused and addressed in the future.
Stage 2: identifying relevant studies
This stage will involve the creation of a comprehensive search strategy for identifying literature from the public databases for answering our research questions. Firstly, the potential main search terms have been determined by reading relevant literatures. Then the initial search strategy was established through discussion by the research team. Lastly, our final search strategy was confirmed after improvement and modification through repeating searches (Additional file 2). According to the final search strategy, we will search the eight widely-used databases including Cochrane Library, PubMed, EMBASE, Web of Science, CNKI, WanFang, CBM and VIP. The search will be run by two reviewers independently. The main keywords used in our search strategy include “COVID19”, “COVID-19”, “COVID2019”, “COVID-2019”, “2019 novel coronavirus infection”, “2019-nCoV”, “coronavirus disease 2019”, “coronavirus disease-19”, “Wuhan coronavirus”, “SARS-CoV-2”, “2019 novel coronavirus”, “Wuhan-Cov”, “Wuhan seafood market pneumonia virus”, “Wuhan virus”, “novel coronavirus pneumonia”, “Severe acute respiratory syndrome-related coronavirus”, “Novel CoV”, “severe acute respiratory syndrome coronavirus 2”, “Vaccination Coverage”, “Vaccin*”, “Vacuna”, “Inoculation”, “Immunization Programs”, etc. Additionally, we will manually check the reference list of included literatures. Although many published COVID-19 reviews searched preprint servers, e.g., bioRxiv (https://www.biorxiv.org/), medRxiv (https://www.medrxiv.org/), we will not to do so as we only include published papers that have been peer-reviewed (even if the article is retracted after publication), whereas preprint servers manuscripts are not peer-reviewed.
Stage 3: study selection
Following the recommendations made by Levac et al , pairs of reviewers will independently screen the titles, abstracts and full-texts to identify potentially relevant studies. We will use literature management software to complete the literature selection process. After deduplication, an online application Rayyan  will be used for screening of abstracts and titles using a process of semi-automation, then Endnote X9 (Thomson Corporation) will be used to assess the eligibility of full-texts. In order to improve the accuracy of the included literature and the consistency of subsequent screening across reviewers, prior to formal screening, the pre-test will be conducted to familiarize the research content and strengthen the understanding for this topic of team members by screening 200 sample records randomly selected. After completing the pre-test, the other records will be screened according to the aforementioned process. Any disagreements during the selection process will be resolved by discussion.
The inclusion and exclusion criteria in our scoping review are as follows: 1) all qualitive, quantitative or mix-method research focusing on COVID-19 vaccines will be included; 2) no limitation on study types, they could be but not limited to guidance documents, basic experiments, clinical studies (e.g., RCTs, cohort studies, cross-sectional studies and case reports), any reviews (e.g., expert reviews, systematic reviews and meta-analyses), conference articles, protocols, and retracted articles (for exploring the issues regarding the integrity of science in the period of COVID-19); 3) we will not limit the research topic for mapping the full landscape for COVID-19 vaccines research, these topics can involve efficacy and safety, cost, public attitudes, views and perceptions, but not limited to that; 4) we will include Chinese and English documents only; 5) we will exclude any news and full-text documents which are not available.
Stage 4: charting the data
A self-developed Excel sheet will be used to extract data, which the relevant information we needed to complete the review. The mainly extracted information including: title, the first author, online or publication date, journal, setting/study location (where the study was conducted), origin/country of corresponding author (where the paper was published), study aim/purpose, study population and sample size, study topic, methodology/method (e.g., framework ), type of vaccines and comparator (if any) and duration of intervention, study type, outcome measures, and important findings or conclusions that relate to our research questions in this scoping review.
Before the formal extraction beginning, pairs of reviewers will pilot the data extraction form by using a sample comprising 10% of the included documents. After the completion of pre-data extraction, the results abstracted by them will be cross-checked and consensus will be sought through discussion, so as to further improve the form until the results are no obvious conflict across data extractors, and then the formal extraction will be completed by pairs of reviewers. Any disagreement will be resolved by discussion within all team members.
In addition, although quality assessment is not required by the scoping review methodology , considering the reliability and application of the study conclusion may be affected by the methodology design and reporting of the study; RCTs, systematic reviews and meta-analyses as important types of evidence will be selected to assess their scientific quality, if possible. Thus, four validated tools, risk of bias 2.0 (RoB 2.0)  and CONSORT 2010, AMSTAR 2 and PRISMA will be used to assess the methodological quality and reporting quality of RCTs, and systematic reviews and meta-analyses, respectively.
Stage 5: collating, summarizing, and reporting results
We will use the PRISMA flow diagram to report the process for literatures screening, the reasons for excluded and final number of included publications in our scoping review. Qualitative synthesis (thematic analysis method ) and descriptive statistics will be used to summarize and present the results. Descriptive statistics (e.g., frequency and percentage) will be used to report the general characteristics (e.g., journal, country, and study type, volume of publications) of included literatures. According to the research contents reported in included documents and study topics they focused on, the COVID-19 vaccines research will be gathered as different themes and their sub-themes (e.g., efficacy and safety, cost, public attitudes, views, and perceptions). In addition, new or updated meta-analysis will be conducted to pool the data available in included primary studies, if relevant.