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 Interactive Network Response System (IWRS) was used to randomized eligible participants prior to study vaccination. The randomization codes were generated by means of block randomization using SAS software. Participants, investigators, and staff undertaking laboratory analyses were masked to group allocation."
Comment: Allocation sequence random Allocation sequence concealed |
| Deviations from intervention |
Some concerns |
Quote: “Double-blinded. The syringes used for injection were identical in appearance and covered with stickers for masking the solution insides. All participants, investigators, clinical research associates, data analyst and laboratory staff were masked to group allocation.”
Comment: Blinded study (participants and personnel/carers) MORTALITY. ADVERSE EVENTS. SERIOUS ADVERSE EVENTS 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. Risk assessed to be low for the outcomes: Mortality. Adverse events. Serious adverse events. NEUTRALIZING ANTIBODY GMT OMICRON Per-protocol analysis was performed on the immunogenicity outcomes. Reasons for exclusion: The immunogenicity analysis was based on immunogenicity full analysis set, which included all participants with valid immunogenicity test results before and after the vaccination. 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. Risk assessed to be some concerns for the outcomes: Neutralizing antibody GMT Omicron. |
| Missing outcome data |
Low |
Comment: 234 participants randomized; 234 participants analyzed for mortality and safety; 221 participants analyzed for immunogenicity.
MORTALITY. ADVERSE EVENTS. SERIOUS ADVERSE EVENTS Data available for all or nearly all participants randomized. Risk assessed to be low for the outcomes: Mortality. Adverse events. Serious adverse events. NEUTRALIZING ANTIBODY GMT OMICRON Data not available for all or nearly all participants randomized for immunogenicity. No evidence that the result is not biased. Reasons: addressed in ROB 2. Missingness could not depend on the true value of the outcome. Risk assessed to be low for the outcomes: Neutralizing antibody GMT OMICRON. |
| 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: Mortality. Neutralizing antibody GMT OMIRCON. Adverse events. Serious adverse events. |
| Selection of the reported results |
Some concerns |
Comment: The protocol, statistical analysis plan and registry were not available.
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 outcome: Mortality. Neutralizing antibody GMT OMICRON. Adverse events. Serious adverse events. |
| Overall risk of bias |
Some concerns |