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: "Participants were randomized at a ratio of 1:1:1 to receive low-dose BNT162b1 or high-dose BNT162b1 or placebo. Participants were stratified by gender, using a web-based interactive response technology (IRT) system. The blocked randomization list was generated by an independent statistician using SAS version 9.4...Authorized unblinded pharmacists prepared the vaccines or placebo according to the allocation of participants through the IRT system, and nurses gave the investigational products to participants."
Comment: Allocation randomized. Allocation concealed. |
| Deviations from intervention |
Low |
Quote: "Authorized unblinded pharmacists prepared the vaccines or placebo according to the allocation of participants through the IRT system, and nurses gave the investigational products to participants. The unblinded staff had no further involvement in the trial, and were forbidden to disclose allocation information to others. All other investigators, participants, laboratory staff and the sponsor remained blinded throughout the trial" (report) "Masking: Triple (Participant, Investigator, Outcomes Assessor)" (registry).
Comment: Blinded study (participants, investigators, outcome assessors) All randomized participants who received at least one dose were analysed for safety outcomes. 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 outcomes: Local adverse events. Systemic adverse events. Adverse events. Withdrawals due to adverse events. |
| Missing outcome data |
Low |
Comment: 144 patients randomized; 144 patients analyzed.
Data available for all participants randomized. Risk assessed to be low for the outcomes: Local adverse events. Systemic adverse events. Adverse events. Withdrawal due to adverse events. |
| Measurement of the outcome |
Low |
Comment: Method of measuring the outcome probably appropriate.
Measurement or ascertainment of outcome does not differ between groups. Blinded study (outcome assessor). Risk assessed to be low for the outcomes: Local adverse events. Systemic adverse events. Adverse events. Withdrawal due to adverse events. |
| Selection of the reported results |
Low |
Comment: The protocol, statistical analysis plan, registry 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. Adverse events. Withdrawal due to adverse events. |
| Overall risk of bias |
Low |