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 |
Low |
Quote: "The participants were sequentially assigned a computer-generated randomization number, and stratified block randomization (block size, 8) by subgroups was adopted." Comment: protocol describes concealed allocation |
| Deviations from intervention |
Low |
Quote: "All the vaccines and placebos were supplied in coded, identical-appearing, single-dose vials." Comment: cointerventions not reported, however unlikely to have affected vaccine efficacy or safety |
| Missing outcome data |
Low |
Comment: 96 randomized / 96 analysed. Flowchart shows all participants included in analysis for safety and immunogenicity |
| Measurement of the outcome |
Low |
Comment: participants self-reported adverse events and were blinded to intervention. Other outcomes are laboratory measures and unlikely to involve judgement. Grading criteria and relationship with intervention of adverse events decided by investigators prior to unblinding. |
| Selection of the reported results |
Low |
Comment: trial protocol and statistical analysis plan available. Outcomes reported are consistent with these. |
| Overall risk of bias |
Low |