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QUESTION
Case control study by Smeeth et al (Lancet 2004) 1294 cases of pervasive developmental disorder (PDD) and 4469 controls were included.
2. Case control study by Smeeth et al (Lancet 2004) 1294 cases of pervasive developmental disorder (PDD) and 4469 controls were included. 1010 cases (78·1%) had MMR vaccination recorded before diagnosis, compared with 3671 controls (82·1%) before the age at which their matched case was diagnosed.
