| Study characteristics |
| Methods |
Cohort study assessing association between MMR and DPPT and asthma or eczema |
| Participants |
Birth cohorts 1988 to 1999 identified through the West Midlands General Practice Research Database (GPRD; N = 16,470, aged from 20 months to 11 years, accounting for 69,602 person‐years) |
| Interventions |
MMR vaccination (data from GPRD; data about other vaccination have also been considered) |
| Outcomes |
Incident diagnoses of asthma/wheeze and eczema were identified using the relevant Oxford Medical Information System (OXMIS, derived from ICD‐8) and Read codes. |
| Funding Source |
Government |
| Notes |
The case definitions used for this study were based on physician‐diagnosed disease and were thus dependent on the child’s being taken to the doctor and receiving a recorded diagnosis. Children who are not taken to the doctor are less likely to be vaccinated and also have less of an opportunity to have a diagnosis of allergic disease recorded. These factors can contribute to show an apparent association between vaccination and allergic reactions. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| PCS/RCS ‐ exposed cohort selection |
Low risk |
Registry West Midlands General Practice ‐ representative of the exposed |
| PCS/RCS ‐ non‐exposed cohort selection |
Low risk |
Registry West Midlands General Practice ‐ drawn from the same community |
| PCS/RCS ‐ comparability |
Low risk |
Adjusted ‐ parental smoking, parental allergic diseases, maternal age, number of older siblings, use of antibiotics early in life of birth, GP practice |
| PCS/RCS ‐ assessment of outcome |
High risk |
The case definitions used for this study were based on physician‐diagnosed disease and were thus dependent on the child’s being taken to the doctor and receiving a recorded diagnosis. |
| Summary Risk of Bias assessment |
High risk |
We had concerns regarding multiple domains such that our confidence in the result is substantially lowered. |
