The urgency to respond to the COVID-19 outbreak has driven an unprecedented surge in preprints that aim to speed up knowledge dissemination as they are available much sooner than peer-reviewed publications. In this study we consider abstracts of research articles and preprints as main entry points that draw attention to the most important information of the document and that try to entice us to read the whole article. In this paper, we try to capture and examine shifts in scientific abstract writing produced at the very beginning of the pandemic. We made a comparative study of abstracts in terms of their informativeness associated with preprints issued in response to the COVID-19 pandemic and those produced in 2019, the closest pre-pandemic period. Our results clearly differ from one preprint server to another and show that there are community-centered habits as regards writing and reporting results. The preprints issued from the arXiv, ChemRxiv and Research Square servers tend to have more informative (generous) abstracts than the ones submitted to the other servers. In four servers, the ratio of structured abstracts decreases with the pandemic.