In Reply: We agree with Drs Edwardes and Baltzan that temporal ecological correlations are not strong evidence, as we stated in our article. However, repeated calls from parents and health care providers convinced us that the suggestion of such a temporal correlation and possible causal relationship between MMR vaccine use and autism occurrence1 had created great concern and that a more detailed examination and presentation of the data was needed.
Dales L, Hammer SJ, Smith NJ. MMR Immunization and Autism—Reply. JAMA. 2001;285(22):2852-2853. doi:10.1001/jama.285.22.2852