The MMR (measles mumps rubella) vaccine was most commonly delayed (45 percent of parents surveyed), and 43 percent of parents postponed the DTaP (diphtheria-tetanus-pertussis) vaccine.
Overall, 2 percent of parents refused all recommended vaccines, and parents most likely to adopt an alternative schedule were those who were not black and who didn't have a regular pediatrician or other health care provider.
About a third of respondents had at one point followed CDC recommendations, then switched to a schedule of their own making.
Meanwhile, 28 percent of parents following the recommended schedule thought delaying some doses might be safer and 22 percent didn't think the official schedule was the best possible schedule.
The main reason for adapting the vaccine schedule seemed to be about safety, Dempsey said.
Dempsey said in her own clinical practice that "people generally tend to delay until after concerns about autism have abated, which is 3- to-4 years of age."
A recent Institute of Medicine report concluded that children's vaccines are typically safe, with bad reactions occurring only rarely and then not causing any lasting problems.
But not all agree that those conclusions are airtight.
"These are not surprising findings and reflect the higher education level of young parents making informed health care decisions for their children today. They are more aware that vaccines are like prescription drugs and carry risks that can be greater for some children than others because, biologically, children are not all the same," said Barbara Loe Fisher, co-founder and president of the National Vaccine Information Center in Vienna, Va.
"The days when people obeyed doctors' orders without question are over. Pediatricians are going to have to get used to answering questions about vaccines and working with parents i
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