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: "Randomization codes were generated individually, and participants were randomly assigned using block randomization with a block size of eight, developed with SAS software (version 9.4). Eligible participants were assigned sequentially to receive one dose of CoronaVac or ZF2001 or no intervention (1:2:1)."
Allocation sequence probably random No information on allocation concealment |
| 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. Hence, deviations did not arise because of the trial context Safety analysis on those who received at least one dose of the intervention: As we are assessing the effect of assignment to intervention, the analysis method performed on these safety outcomes, was considered appropriate. [go to Risk assessed to be low for the outcomes: Local adverse events. Systemic adverse events. Adverse events. Per-protocol analysis was performed on the immunogenicity outcomes. Reasons for exclusion: of 41 assigned to receive CoronaVac: 1 absence of blood sample; hemolysis in blood samples taken from one participant in the control group) 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 number Risk assessed to be low for the outcomes: Specific antibody GMT. Neutralizing antibody GMT. |
| Missing outcome data |
Low |
Comment: 122 participants randomized; 122 participants analyzed
Data available for all or nearly all participants randomized. Risk assessed to be low for the outcomes: Specific antibody GMT. Neutralizing antibody GMT. Local adverse events. Systemic adverse events. 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) br/> SPECIFIC ANTIBODY GMT, NEUTRALIZING ANTIBODY GMT Observer-reported outcome not involving judgement. Risk assessed to be low for the outcomes: Specific antibody GMT. Neutralizing antibody GMT. LOCAL, SYSTEMIC, ADVERSE EVENTS The authors reported on adverse events that may contain both clinically- 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. Withdrawals due to adverse events. |
| Selection of the reported results |
Some concerns |
Comment: The registry was retrospective.
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: Specific antibody GMT. Neutralizing antibody GMT. Local adverse events. Systemic adverse events. Adverse events. Withdrawal due to AE. |
| Overall risk of bias |
Some concerns |