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: “Randomization using a web-based randomization system hosted by the Singapore Clinical Research Institute (SCRI), in which a randomization list with randomized permuted blocks will be generated by the trial statistician.”
Comment: Allocation sequence random. Allocation sequence concealed. |
| Deviations from intervention |
Low |
Quote: “Single-blind”
Comment: Partially blinded study (participants) Deviations from intended intervention arising because of the study context: No participant cross-over. Hence, deviations did not arise because of the trial context. Safety analysis on those who received at least one dose of the intervention. This method was considered appropriate to estimate the effect of assignment to intervention. Risk assessed to be low for the outcomes: Local adverse events. Systemic adverse events. Adverse events. Serious adverse events. |
| Missing outcome data |
Some concerns |
Comment: 100 participants randomized; 98 participants analyzed for safety; 91 participants analyzed for reactogenicity.
Data available for all or nearly all participants randomized for safety. Data not available for all or nearly all participants randomized for reactogenicity. No evidence that the result is not biased. Reasons: not clear. Missingness could depend on the true value of the outcome. Not likely that missingness depended on the true value of the outcome due to balance between arms. Risk assessed to be low for the outcomes: Adverse events. Serious adverse events. Risk assessed to be some concerns for the outcomes: Local adverse events. Systemic 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) LOCAL, SYSTEMIC, ADVERSE 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. Adverse events. Serious adverse events. |
| Selection of the reported results |
Some concerns |
Comment: The protocol and statistical plan are not available. The retrospective registry is available (December 2, 2021).
No information on whether the results were 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: Local adverse events. Systemic adverse events. Adverse events. Serious adverse events. |
| Overall risk of bias |
Some concerns |