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 stratified block randomization and intragroup double-blind design are adopted in both studies. The candidate vaccine and placebo control within each dose group are set at a ratio of 5:1.Group allocation was not known to investigators, participants and biological sample testing personne" Allocation probably random Unclear allocation concealment Risk assessed as some concerns |
| Deviations from intervention |
Low |
QUOTE: “Group allocation was not known to investigators, participants and biological sample testing personnel” (publication); “Triple (Participant, Care Provider, Investigator)” (trial registry). Comment: Blinded study (participants and personnel/carers) Data for the outcome were analyzed using intention-to-treat analysis. This method was considered appropriate to estimate the effect of assignment to intervention. Risk assessed as low for the outcomes: specific Ab GMT. nAb GMT. Local adverse events. Systemic adverse events. Adverse events. Serious adverse events. |
| Missing outcome data |
Low |
Comment: 960 participants randomized; 959 participants analyzed for safety outcome/952 participants analyzed for immunogenicity outcomes. Data available for all participants randomized. Risk assessed as low for the outcomes: specific Ab GMT. nAb GMT. Local adverse events. Systemic adverse events. Adverse events. Serious adverse events. |
| 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 as low for the outcomes: specific Ab GMT. nAb GMT. Local adverse events. Systemic adverse events. Adverse events. Serious adverse events. |
| Selection of the reported results |
Low |
Comment: The prospective registry was available (November 23, 2020) The protocol and statistical analysis plan were not available at the time of data extraction. Outcomes pre-specified. Results were not selected from multiple outcome measurements or analyses of the data. Trial analyzed as pre-specified Risk assessed as low for the outcomes: specific Ab GMT. nAb GMT. Local adverse events. Systemic adverse events. Adverse events. Serious adverse events. |
| Overall risk of bias |
Some concerns |