172 studies identified by a systematic review after screening more than 20,000 articles (on title and summary, then on 604 full-text) and 44 comparative studies selected for the meta-analysis, distributed in 16 countries on all continents. No randomized study was found. 66 studies evaluated the impact of social distancing linked to the infection, 30 studies focused on masks and 13 studies on eye protection. Only 16% of the included studies involved the SARS-CoV-2 study. Social distancing : strong association with the risk of infection, with an absolute risk of 12.8% with a short distance (<1m) versus 2.6% with a greater distance: aOR = 0.18 [95% CI: 0 , 09 to 0.38]. The strength of the association increases with distance with an RR increased by 2 per meter. Use of masks: strong reduction of the risk of infection with an absolute risk of 3.1% with a mask versus 17.4% without mask: aOR = 0.15 [95% CI: 0.07 to 0.34]. This reduction more important when masks are used in a healthcare context: RR = 0.30 against RR = 0.56 for public places. Similarly, the use of the FFP2 mask almost fully reduces the risk of infection compared to other masks: aOR = 0.04 vs aOR = 0.33 for other masks. Eye protection: strong reduction of the risk of infection with an absolute risk is 5.5% with protection versus 16.0% without: aOR = 0.22 [95% CI: 0.12 to 0.39].
The results of this systematic review with meta-analysis showed a 4-fold reduction of the risk with a distance of at least 1 meter, and an inverse propotional relation between the risk and the distance. Also, the use of masks, even in the general population, lead to a 7-fold reduction of the risk of infection, especially if used in the context of healthcare or if an FFP2 mask was used. Finally, that the use of eye protection reduced the risk of infection by a factor of 4.
- Systematic review with well-conducted research strategy
- Meta-analysis with robust statistics
- No randomized study found, only observational studies
- Strong heterogeneity between studies and possible publication bias not really assessed (no funnel plot for example)
- Inclusion of articles about infection with other coronaviruses (SARS and MERS)
- Inclusion of probable cases (not only confirmed cases)
Study the efficiency of social distancing, face masks and eye protection on the transmission of SARS-CoV-2 in public places and in health structures.
Systematic literature review and meta-analysis based on Cochrane recommendations and the GRADE approach (protocol recorded in Prospero) Bibliographic research conducted on May 3, 2020 on many platforms including MEDLINE and Embase with inclusion of articles describing patients infected with SARS-CoV-2, SARS-CoV or MERS-CoV and with description of the protective measures: distancing, eye protection or mask (surgical, FFP2 or consumer mask in reusable cotton).
Judgment criteria: risk of transmission, hospitalizations, admission to intensive care, death, time to clinical recovery, adverse effects of medical interventions Data analysis: calculation of pooled RRs or ORs adjusted according to the data available in observational studies (no randomized trial found). Evaluation of heterogeneity via GRADE (no calculation of I ^ 2). Analysis in subgroups according to distances via univariate meta-regressions with random effect. Use of interaction test (10,000 randomized permutations per Monte Carlo model) and 2 sensitivity analyzes including a Bayesian meta-analysis.
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