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 |
Some concerns |
Quote: “The blocked randomization list was created from the sealed envelope, an online software application. Open-label.”
Comment: Allocation sequence random. No information on allocation concealment. |
Deviations from intervention |
Some concerns |
Quote: "open-label" trial.
Comment: Unblinded study (participants and personnel/carers). Deviations from intended intervention arising because of the study context: No participant cross-over. Hence, deviations did not arise because of the trial context. Per-protocol analysis was performed on the outcomes. Reasons for exclusion: 8 participants were infected with SARS-COV-2 at baseline. As we are assessing the effect of assignment to intervention (intention-to-treat effect), we considered that the data were analyzed inappropriately. There was probably no substantial impact of failure to analyze participants according to their randomized assignment due to the small numbers. Risk assessed to be some concerns for the outcomes: Neutralizing antibody GMT-Omicron, Local adverse events, Systemic adverse events, and Serious adverse events. |
Missing outcome data |
Low |
Comment: 210 participants randomized; 200 participants analyzed.
Data available for nearly all participants randomized. Risk assessed to be low for the outcomes: Neutralizing antibody GMT-Omicron, Local adverse events, Systemic adverse events, and Serious 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). NEUTRALIZING ANTIBODY GMT-OMICRON Observer-reported outcome not involving judgement. Risk assessed to be low for the outcomes:Neutralizing antibody GMT-Omicron. LOCAL, SYSTEMIC, and SERIOUS ADVERSE EVENTS The authors reported on adverse events that may contain both clinically- and laboratory-detected events, which can be influenced by knowledge of the intervention assignment, but is not likely in the context of the pandemic. Risk assessed to be some concerns for the outcomes: Local adverse events, Systemic adverse events, and Serious adverse events. |
Selection of the reported results |
Some concerns |
Comment: The registry was retrospective (dated July 20, 2021). No information on whether the result was selected from multiple outcome measurements or analyses of the data. No information on whether the trial was analyzed as pre-specified. Risk assessed to be some concerns for the outcomes: Neutralizing antibody GMT-Omicron, Local adverse events, Systemic adverse events, and Serious adverse events. |
Overall risk of bias |
Some concerns |