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 Cenduit Interactive Response Technology system (IQVIA, Durham, NC, USA) was used to randomly assign participants (1:1), using a block size of six, to receive two doses of either SCB-2019 or placebo. The randomisation lists were generated by external unmasked statisticians who played no further role in endpoint analyses."
Comment: Allocation sequence random. Allocation sequence concealed. Imbalances in baseline characteristics appear to be compatible with chance. Risk assessed to be low. |
| Deviations from intervention |
Low |
Quote: “Observer-blinded” [report]; "Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)" [registry] Comment: Blinded study (participants and personnel/carers) Per-protocol analysis was performed on the efficacy outcomes. 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 similar reasons and proportions between arms. Risk assessed to be some concerns for the outcomes: Confirmed symptomatic COVID against Delta variant. |
| Missing outcome data |
Some concerns |
Comment: 24,141 participants randomized; 24,076 participants analyzed for safety; 20,090 participants analyzed for efficacy; 7,819 participants analyzed for reactogenicity. Data not available for all or nearly all participants randomized for efficacy or reactogenicity. No evidence that the result is not biased.
This potential source of risk of bias has been taken into account in domain 2. Variant classification: 157 cases identified /114 cases sequenced and classified 72.60% of cases analyzed for variants. Risk assessed to be Some concerns for the outcome: Confirmed symptomatic against Delta variant. |
| Measurement of the outcome |
Low |
Comment: Method of measuring the outcome probably appropriate. Measurement or ascertainment of outcome probably does not differ between groups. Blinded study (outcome assessor). Risk assessed to be low for the outcomes: Confirmed symptomatic COVID agaisnt Delta variant. |
| Selection of the reported results |
Low |
Comment: The prospective registry was available. 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 outcomes: Confirmed symptomatic COVID against Delta variant. |
| Overall risk of bias |
Some concerns |