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: "Eligible adult KT recipients were randomized using a stratified (by previous vaccine regimen) block randomization approach."
Comment: Allocation sequence probably random. No information on allocation concealment. |
| Deviations from intervention |
Some concerns |
Quote: “non-blinded”
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:Losses to follow-up and receipt of non-allocated vaccines on request. 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 small numbers involved. Risk assessed to be some concerns for the outcomes: Cellular response. Local adverse events. Systemic adverse events. Adverse events. Serious adverse events. |
| Missing outcome data |
Some concerns |
Comment: 85 participants randomized; 77 participants analyzed.
Data not available for all or nearly all participants randomized. No evidence that the result is not biased. Reasons: One patient from the viral vector group later withdrew their consent, and seven patients were lost during follow-up (four and three patients in the Viral vector and MRNA groups, respectively). Missingness could depend on the true value of the outcome. Not likely that missingness depended on the true value of the outcome due to similar numbers between arms. Risk assessed to be some concerns for the outcomes: Cellular response. Local adverse events. Systemic adverse events. Adverse events. 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) CELLULAR RESPONSE Observer-reported outcome not involving judgement. Risk assessed to be low for the outcomes: Cellular response. 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 |
Low |
Comment: The prospective registry was available.
Outcome 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: Cellular response. Local adverse events. Systemic adverse events. Adverse events. Serious adverse events. |
| Overall risk of bias |
Some concerns |