The COVID-19 pandemic has been characterized by an unprecedented amount of published scientific articles. The aim of this study is to assess the type of articles published during the first 3 months of the COVID-19 pandemic and to compare them with articles published during 2009 H1N1 swine influenza pandemic. Two operators independently extracted and assessed all articles on COVID-19 and on H1N1 swine influenza that had an abstract and were indexed in PubMed during the first 3 months of these pandemics. Of the 2482 articles retrieved on COVID-19, 1165 were included. Over half of them were secondary articles (590, 50.6%). Common primary articles were: human medical research (340, 59.1%), in silico studies (182, 31.7%) and in vitro studies (26, 4.5%). Of the human medical research, the vast majority were observational studies and cases series, followed by single case reports and one randomized controlled trial. Secondary articles were mainly reviews, viewpoints and editorials (373, 63.2%). Limitations were reported in 42 out of 1165 abstracts (3.6%), with 10 abstracts reporting actual methodological limitations. In a similar timeframe, there were 223 articles published on the H1N1 pandemic in 2009. During the COVID-19 pandemic there was a higher prevalence of reviews and guidance articles and a lower prevalence of in vitro and animal research studies compared with the H1N1 pandemic. In conclusions, compared to the H1N1 pandemic, the majority of early publications on COVID-19 does not provide new information, possibly diluting the original data published on this disease and consequently slowing down the development of a valid knowledge base on this disease. Also, only a negligible number of published articles reports limitations in the abstracts, hindering a rapid interpretation of their shortcomings. Researchers, peer reviewers, and editors should take action to flatten the curve of secondary articles.

中文翻译：

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大流行最初 3 个月内发表的有关 COVID-19 的科学文章的特征

COVID-19 大流行的特点是发表的科学文章数量空前。本研究的目的是评估在 COVID-19 大流行的前 3 个月内发表的文章类型，并将其与 2009 年 H1N1 猪流感大流行期间发表的文章进行比较。两名操作员独立提取和评估了所有关于 COVID-19 和 H1N1 猪流感的文章，这些文章有摘要并在这些大流行的前 3 个月被 PubMed 索引。在 COVID-19 上检索到的 2482 篇文章中，有 1165 篇被收录。其中超过一半是二手文章（590 篇，50.6%）。常见的主要文章有：人类医学研究 (340, 59.1%)、计算机研究 (182, 31.7%) 和体外研究 (26, 4.5%)。在人类医学研究中，绝大多数是观察性研究和病例系列，其次是单个病例报告和一项随机对照试验。次要文章主要是评论、观点和社论（373篇，63.2%）。1165 篇摘要中有 42 篇（3.6%）报告了局限性，其中 10 篇摘要报告了实际的方法学局限性。在类似的时间范围内，2009 年发表了 223 篇关于 H1N1 大流行的文章。与 H1N1 大流行相比，在 COVID-19 大流行期间，评论和指导文章的流行率较高，体外和动物研究的流行率较低。总之，与 H1N1 大流行相比，大多数关于 COVID-19 的早期出版物没有提供新信息，可能会稀释有关该疾病的原始数据，从而减缓有关该疾病的有效知识库的发展。还，只有极少数已发表的文章报告了摘要中的局限性，从而阻碍了对其缺点的快速解释。研究人员、同行评审员和编辑应采取行动，使二级文章的曲线变平。