Arvelo 2009 USA.
| Methods | Case‐control study | |
| Participants | Case LDC: LDC with a secondary attack rate of shigellosis ≥ 2% (median 5%; range 2–25%), n = 18 Control LDCs: LDC with a secondary attack rate < 2% (median 0; range 0–1.2%), n = 21 |
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| Interventions | Risk factor of interest:
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| Outcomes | Daycare centre with a secondary attack rate of shigellosis (shigellosis case was defined as a person with any Shigella species isolated from stool) ≥ 2%. | |
| Notes | Location: 39 LDCs in Kansas City metropolitan area, USA Length: 2 months (October to November 2005) Publication status: journal |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | NA |
| Allocation concealment (selection bias) | Unclear risk | NA |
| Blinding of participants and personnel (performance bias) All outcomes | Unclear risk | NA |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | NA |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | NA |
| Selective reporting (reporting bias) | Unclear risk | NA |
| Other bias | Unclear risk | NA |
| Similarity of baseline outcome measurements | Unclear risk | NA |
| Similarity of baseline characteristics | Unclear risk | NA |
| Adequate allocation of intervention concealment during the study | Unclear risk | NA |
| Adequate protection against contamination | Unclear risk | NA |
| Confounders adequately adjusted for in analysis/design | Unclear risk | NA |
| Recruitment bias | Unclear risk | NA |
| Baseline imbalance | Unclear risk | NA |
| Loss of clusters | Unclear risk | NA |
| Incorrect analysis | Unclear risk | NA |