Objective: Infodemic, a neologism characterizing an excess of fast-tracked low quality publications, has been employed to depict the scientific research response to the COVID19 crisis. The concept relies on the presumed exponential growth of research output. This study aimed to test the COVID19 infodemic claim by assessing publication rates and patterns of COVID19-related research and a control, a year prior. Design: A Reproduction Number of Publications (Rp) was conceived. It was conceptualized as a division of a week incidence of publications by the average of publications of the previous week. The publication growth rates of preprint and MEDLINE-indexed peer-reviewed literature on COVID19 were compared using the correspondent Influenza output, a year prior, as control. Rp for COVID19 and Influenza papers and preprints were generated and compared and then analyzed in light of the respective growth patterns of their papers and preprints. Main outcomes: Output growth rates and Reproduction Number of Publications (Rp). Results: COVID19 peer-reviewed papers showed a fourteen fold increase compared to Influenza papers. COVID19 papers and preprints displayed an exponential growth curve until the 20th week. COVID19 papers displayed Rp=3.17±0.72, while the control group presented Rp=0.97±0.12. Their preprints exhibited Rp=2.18±0.54 and Rp=0.97±0.27 respectively, with no evidence of exponential growth in the control group, as its Rp remained approximately one. Conclusions: COVID19 publications displayed an epidemic pattern. As the growth patterns of COVID19 peer-reviewed articles and preprints were similar, and the majority of the COVID19 output came from indexed journals, not only authors but also editors appear to had played a significant part on the infodemic. Review protocol: https://osf.io/q3zkw/?view_only=ff540dc4630b4c6e9a2639d732047324 Ethical aspects: No ethical clarence was required as all analyzed data were publicly available.

Scientific paradigm violations are common in the medical literature. This article aims to describe the principles that should guide scientific thinking, such as the philosophy of skepticism, the consideration of multiple hypothesis, epidemiological criteria to demonstrate association, concern about random errors and the need to quantify the strength of association. We use the hypothesis of causality between Zika and microcephaly to illustrate these principles and cognitive mechanisms that predispose to its violation. This is an example of dissociation between certainty and level of evidence, since the association between these two entities was confirmed at a time when there was no evidence of quality that supported this association.