Autism was reported for 17,348/916,331 (1.9%) children aged 0–15, and 7,715/632,488 (1.2%) young people aged 16–24. The rate increased to age 11 in boys and age 10 in girls, reflecting age at diagnosis. Prevalence was 2.8% at age 10 (4.4% for boys; 1.1% for girls), and 2.9% at age 11 (4.5% for boys; 1.1% for girls). 22.0% of children and 25.5% of young people with autism reported poor health, compared with 2.0% and 4.4% without autism. Autism had an odds ratio of 11.3 (95% CI 11.0 to 11.7) in predicting poor health. Autistic females had poorer health than autistic males, with odds ratio for female gender reported at 1.6 (95% CI 1.5 to 1.8).