Derek Chu and colleagues1 examined whether physical distancing, face masks, and eye protection could prevent transmission of SARS-CoV-2. We are concerned that some of the data from the included preprints were out of date, affecting the results of the meta-analysis.
The systematic review included literature up to May 3, 2020. Seven articles, including four preprints, described the comparison of the risk of SARS-CoV-2 transmission between far and short physical distancing. Further physical distancing was associated with a lower risk of SARS-CoV-2 transmission (relative risk [RR] 0·15 compared with shorter physical distancing, 95% CI 0·03–0·73, I 2=59%; appendix).
We followed up on the status of the four preprints and found that one of them2 was published online on May 1, 2020,3 before the search cutoff date. The published version used a larger dataset (n=227 vs n=83 in the preprint), and the risk of SARS-CoV-2 transmission was almost equal between the physical distancing groups (RR 0·99 vs RR 0·55 in the preprint).
We updated the meta-analysis, replacing the results from the preprint by the corresponding published study.3 The association between physical transmission and the risk of SARS-CoV-2 transmission became less evident (RR 0·16, 95% CI 0·02–1·06, I 2=70%; appendix).
Non-peer-reviewed preprints might be based on preliminary data that are later updated. We recommend that systematic reviews should check the latest situation of each included preprint, if necessary by contacting the authors, to ensure that the results are up to date.
© 2021 Pavlo Gonchar/SOPA Images/LightRocket/Getty Images
We declare no competing interests.
Supplementary Material
References
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