| Study characteristics |
| Methods |
Case‐only ecological method |
| Participants |
1 October 2003 was chosen as the survey date. As of 1 October 2003, a total of 27,749 children were registered within the Lester B. Pearson School Board (LBPSB), the largest school board for Anglophone children in Quebec. The LBPSB has 55 schools (45 elementary and 10 secondary) and provides education from kindergarten through grade 11. Age 5 to 16. |
| Interventions |
MMR doses, at 12 and 18 months of age. Data on MMR uptake for the study period were available through the Direction de Santé Publique de la Capitale Nationale (N Boulianne, BN, MSc, written communication, 2005). These data were routinely collected in the region of Quebec amongst 5‐year‐old children attending kindergarten during the years 1993 to 2004 (i.e. for birth cohorts from 1988 to 1998). Vaccination records from children were used as the main source of information to document MMR vaccination and its date. When this information was not available, vaccination status of the children was obtained through consultation of the regional vaccination registry or else through direct contact with doctors' practices, both from community clinics and private offices. |
| Outcomes |
Children with a diagnosis of PDD were identified by school personnel and given a study code to preserve the anonymity of the data. Children’s diagnoses were not verified by direct assessments, but it is worth noting that a majority of these children (N = 155; 86.1%) were diagnosed at the Montreal Children’s Hospital. School personnel further identified the diagnostic subtype using DSM‐IV diagnostic criteria, age, grade, and school the child was attending. When available, place of birth was also recorded. |
| Funding Source |
Government |
| Notes |
|
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| COEM ‐ case selection |
Low risk |
Adequate ‐ independent validation |
| COEM ‐ exposure |
Low risk |
Adequate ‐ secure record ‐ vaccination record |
| COEM ‐ time trend comparison |
Low risk |
Adequate ‐ well‐defined |
| COEM ‐ comparability |
Low risk |
Adequate ‐ adjusted by birth cohort, level of ethylmercury |
| Summary Risk of Bias assessment |
Low risk |
|
