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 is adjusted for age, self-reported race, body mass index and current smoking; did not adjust for health seeking behaviour, co-morbitities, SES, time. Study was restricted to pregnant women. |
| Selection of participants into the study |
Low |
No particular concerns in this domain. |
| Clasification of interventions |
Low |
No concerns in this domain - vaccination status was extracted from medical records. |
| Deviations from intervention |
Low |
No concerns in this domain - the study was observational. |
| Missing outcome data |
Low |
No concerns in this domain. |
| Measurement of the outcome |
Moderate |
Testing behaviour is likely to be associated with vaccination status. |
| Selection of the reported results |
Moderate |
There is no evidence of a protocol or statistical analysis plan, and we have concerns that results could have been selected for reporting because of the findings. |
| Overall risk of bias |
Serious |
|
| Overall comment | The published report was used in data extraction and risk of bias assessment. Roughly 2% of control group were partially vaccinated. Vaccine types were: Pfizer 66%, Moderna 29%, and Janssen 5%.
The main concern is the potential for uncontrolled confounding. There is also a potential issue with measuring infection status as testing behaviour may be influenced by vaccination status. |