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 |
| Confounding |
Serious |
The analysis adjusted for age (60 to 69 years, 70 to 79 years, and ≥80 years), sex, demographic group (general Jewish, Arab, or ultra-Orthodox Jewish population), the date of the second vaccine dose and calendar date. Uncontrolled confounding is likely as the following were not adjusted for: socioeconomic status, health seeking behaviour, specific populations, comorbidities, calendar time, covid symptoms at time of potential vaccination or hospitalization and need for healthcare. The authors potentially also did not account for geographic location (note that ethnicity was measured using statistical area of residence). |
| Selection of participants into the study |
Low |
No particular concerns in this domain. |
| Clasification of interventions |
Low |
No particular concerns in this domain - vaccination status is likely to be adequately measured. |
| Deviations from intervention |
Low |
No concerns in this domain - the study was observational. |
| Missing outcome data |
Low |
No concerns in this domain - a small number of participants were excluded for missing data on sex. |
| Measurement of the outcome |
Low |
No particular concerns in this domain - determination of outcomes is unlikely to be biased. |
| Selection of the reported results |
Low |
No concerns in this domain - a study protocol was available. |
| Overall risk of bias |
Serious |
|
| Overall comment | Concerns about uncontrolled confounding. |