Summary of findings 9. Safety: autistic spectrum disorders.
| Safety: autistic spectrum disorders | ||||||
| Patient or population: children 9 months to 15 years old Setting: general population Intervention: MMR vaccine Comparison: unvaccinated | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | № of participants (studies) | Certainty of the evidence (GRADE) | Comments | |
| Risk of ASD amongst unvaccinated | Risk of ASD amongst vaccinated | |||||
| Cohort studies ‐ all children, MMR | Study population | Rate ratio 0.93 (0.85 to 1.01) | 1,194,764 (2 observational studies) | ⊕⊕⊕⊝ MODERATE1 | ||
| 451 per 100,000 | 419 per 100,000 (383 to 455) | |||||
| Cohort studies ‐ autism risk (low), MMR | Study population | Rate ratio 1.00 (0.89 to 1.14) | 93,071 (1 observational study) | ⊕⊕⊕⊝ MODERATE1 | ||
| 85 per 100,000 | 85 per 100,000 (76 to 97) | |||||
| Cohort studies ‐ autism risk (moderate/high), MMR | Study population | Rate ratio 0.80 (0.64 to 0.98) | 1914 (1 observational study) | ⊕⊕⊝⊝ LOW | The apparent protective effect is due to indication bias. | |
| 12 per 1000 | 9 per 1000 (7 to 11) | |||||
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). ASD: autism spectrum disorders; CI: confidence interval; MMR: measles, mumps, rubella vaccine | ||||||
| GRADE Working Group grades of evidence High certainty: We are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: We are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: Our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: We have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect. | ||||||
1Upgraded one level due to residual confounding ‐ confounding expected to increase the effect but no effect was observed.