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 randomisation statisticians used SAS statistical software (version 9.4) to generate the random table of participants in each dose group. These randomisation statisticians were not allowed to participate in other related work of these clinical trials and not allowed to disclose the blind code to any personnel participating in this clinical trial. The participants were randomly assigned to the experimental vaccine group or the placebo group according to the block randomisation method, with the block and block size of 5 and 5, respectively, in phase 1 trial, and of 75 and 12, respectively, in phase 2 trial. Investigators at trial site assign study numbers strictly according to the order of screening sequence of eligible subjects, and experimental vaccines were obtained and administered according to the numbers."
Comment: Allocation sequence random. Allocation concealed. Imbalances in baseline characteristics appear to be compatible with chance |
| Deviations from intervention |
Low |
Quote: “The participants, field investigators and laboratory team were always blinded to group allocation during the trial.” Comment: Double-blinded study (patients and physicians). Data were analyzed using intention-to-treat analysis for safety. Risk assessed to be low for the outcomes: Local adverse events. Systemic adverse events. Withdrawal due to adverse events. Adverse events. Serious adverse events. |
| Missing outcome data |
Low |
Comment: 900 randomized; 900 analyzed for adverse events. Data available for all or nearly all participants randomized. Risk assessed to be low for the outcomes: Local adverse events. Systemic adverse events. Withdrawal due to 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. Comment: Blinded study (laboratory personnel, participants, investigators). Risk assessed to be low for the outcomes: Local adverse events. Systemic adverse events. Withdrawal due to adverse events. Adverse events. Serious adverse events. |
| Selection of the reported results |
Low |
Comment: The trial registry, protcol and statistical plan were available.
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: Local adverse events. Systemic adverse events. Withdrawal due to adverse events. Adverse events. Serious adverse events. |
| Overall risk of bias |
Low |