Note: The risk of bias by domain corresponds to the highest risk of bias among outcomes by domain.
The overall risk of bias corresponds to the overall highest risk of bias assessed among outcomes.
| Bias | Author's judgement | Support for judgement |
| Randomization |
Low |
Quote: Each room was ordered sequentially numbered by block and floor, and imported into statistical computer software Stata V.16 which randomly allocated floors to interventions and control prior to study initiation. Information on cluster allocation was concealed by a study statistician who informed the study team of the assigned intervention and floor a day prior to recruitment to facilitate preparations. Comment: Allocation sequence random.Allocation sequence probably concealed. |
| Deviations from intervention |
Low |
Quote: Open-label
Comment: Unblinded study (participants and personnel/carers) Deviations from intended intervention arising because of the study context: No participant cross-over. Data for the outcome were analyzed using modified intention-to-treat analysis, following exclusion of participants found to be seropositive at baseline. This method was considered appropriate to estimate the effect of assignment to intervention. Risk assessed to be low for the outcomes: Confirmed COVID-19. Symptomatic confirmed COVID-19. Hospital admissions or death. ICU admissions or death. Mortality. Adverse events. |
| Missing outcome data |
Some concerns |
Comment: 3408 participants randomized; 3037 participants analyzed.
Data not available for all or nearly all participants randomized. No evidence that the result is not biased. Reasons: 359 were excluded from analysis due to seropositivity at baseline (accounted for in domain 2); 12 participants withdrew from the study. Missingness could depend on the true value of the outcome. Not likely that missingness depended on the true value of the outcome (less than 1% of missing data). Risk assessed to be some concerns for the outcomes: Confirmed COVID-19. Symptomatic confirmed COVID-19. Hospital admissions or death. ICU admissions or death. Mortality. Adverse events. |
| Measurement of the outcome |
Some concerns |
Comment: Method of measuring the outcome probably appropriate.
Measurement or ascertainment of outcome probably does not differ between groups. Unblinded study (outcome assessor) CONFIRMED COVID-19, CONFIRMED SYMPTOMATIC COVID-19, MORTALITY Mortality and PCR status do not involve judgement. Risk assessed to be low for outcome: Confirmed COVID-19. Confirmed symptomatic COVID-19. Mortality. ICU ADMISSION OR DEATH For this outcome, we do not consider that the assessment cannot possibly be influenced by knowledge of intervention assignment. Risk assessed to be low for the outcome: ICU admission or death. HOSPITAL ADMISSION OR DEATH, ADVERSE EVENTS Although mortality does not involve judgement, hospital admission could be influenced by knowledge of intervention assignment but was not considered likely to in the context of a pandemic. Adverse events may contain clinically-detected and patient-reported outcomes which can be influenced by knowledge of intervention assignment but is not considered likely to in the context of a pandemic. Risk assessed to be some concerns for the outcomes: Hospital admission or death. Adverse events. |
| Selection of the reported results |
Some concerns |
Comment: The trial registry was available, but was retrospective (dated JUne 24th, 2020).
No information on whether the result was selected from multiple outcome measurements or analyses of the data. Trial probably not analyzed as pre-specified. Risk assessed to be some concerns for outcomes: Confirmed COVID. Symptomatic confirmed COVID. Hospital admissions or death. ICU admissions or death. Mortality. Adverse events. |
| Overall risk of bias |
Some concerns |