| Study characteristics |
| Methods |
Nationwide cohort study ‐ Denmark |
| Participants |
657,461 children born in Denmark from 1999 through 31 December 2010, with follow‐up from 1 year of age and through 31 August 2013. |
| Interventions |
MMR1 and MMR2 vaccinations and other childhood vaccinations administered in the first year of life. There were no thimerosal‐containing vaccines in the Danish programme during the study period. The specific MMR vaccine used in the study period contained the following vaccine strains: Schwarz (measles, 2000 to 2007) or Enders' Edmonston (measles, 2008 to 2013), Jeryl Lynn (mumps), and Wistar RA 27/3 (rubella). |
| Outcomes |
Danish population registries were used to link information on MMR vaccination, autism diagnoses, other childhood vaccines, sibling history of autism, and autism risk factors to children in the cohort. Survival analysis of the time to autism diagnosis with Cox proportional hazards regression was used to estimate hazard ratios of autism according to MMR vaccination status, with adjustment for age, birth year, sex, other childhood vaccines, sibling history of autism, and autism risk factors (based on a disease risk score). |
| Funding Source |
Government |
| Notes |
|
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| PCS/RCS ‐ exposed cohort selection |
Low risk |
Adequate ‐ Danish population registries ‐ representative of the exposed |
| PCS/RCS ‐ non‐exposed cohort selection |
Low risk |
Adequate ‐ Danish population registries ‐ from the same community |
| PCS/RCS ‐ comparability |
Low risk |
Adequate ‐ multivariate model ‐ age, sex, other childhood vaccines received, sibling history of autism, and autism risk score |
| PCS/RCS ‐ assessment of outcome |
Low risk |
Adequate ‐ Danish Psychiatric Central Register |
| Summary Risk of Bias assessment |
Low risk |
Plausible bias is unlikely to have seriously altered the results. |
