My 3-year-old has autism. should my 1-year-old's vaccine schedule be different because of this?

No. Research has : shown no difference in the incidence of ASD in fully/delayed/unimmunized younger siblings. All younger sibs need frequent developmental assessments till age 3, as 32% of brothers & 19% of sisters are diagnosed with ASD, if no genetic cause is found on DNA Probe for Fragile X or Chromosomal Microarray in the older sib to increase risk. Up to 40% of younger sibs have language delays. See below.