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: “Participants were randomized.”
Comment: Allocation sequence probably random. No information on allocation concealment. |
Deviations from intervention |
Low |
Quote: “Double-blind.”
Comment: Unclear blinding (participants blinded and unclear if personnel/carers blinded) Deviations from intended intervention arising because of the study context: No participant cross-over. Hence, deviations did not arise because of the trial context. ITT analysis (with N randomized denominators) was used for safety and some immunogenicity outcomes. Cellular response was assessed in predefined subgroups of ten participants in each arm. As we are assessing the effect of assignment to intervention, the analysis method performed on these outcomes, was considered appropriate. Risk assessed to be low for the outcomes: Specific antibody GMT. Cellular response. Local adverse events. Systemic adverse events. |
Missing outcome data |
Some concerns |
Comment: 76 participants randomized; 76 participants analyzed for sAb immunogenicity and safety; 37 participants analyzed for cellular response.
Data available for all or nearly all participants randomized for nAb immunogenicity and safety. Data not available for all or nearly all participants randomized for cellular response. Reasons: Cellular response analysis conducted in a subgroup of each arm (>5% missing). No evidence that the result is not biased. Missingness could depend on the true value of the outcome. Not likely that missingness depended on the true value of the outcome. Risk assessed to be low for the outcomes: Specific antibody GMT. Local adverse events. Systemic adverse events. Risk assessed to be some concerns for the outcomes: Cellular response. |
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. Unclear blinding (outcome assessor). SPECIFIC ANTIBODY GMT, CELLULAR RESPONSE Observer-reported outcome not involving judgement. Risk assessed to be low for the outcomes: Specific antibody GMT. Cellular response. LOCAL, SYSTEMIC 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. |
Selection of the reported results |
Low |
Comment: The prospective registry was available (Date September 23rd, 2021).
Outcomes pre-specified. Results were not selected from multiple outcome measurements or analyses of the data. Trial analyzed as pre-specified. Risk assessed to be low for the outcome: Specific antibody GMT.Cellular response. Local adverse events. Systemic adverse events. |
Overall risk of bias |
Some concerns |