More than one in ten parents uses an "alternative" vaccination schedule for their young children, including refusing vaccines altogether, according to a U.S. survey.
Based on the findings, researchers worry that more parents may be refusing vaccines in the future—raising the risk that diseases like measles and whooping cough will spread in schools and communities.
"The vaccines that we recommend have been so effective in largely eliminating the vaccine-preventable diseases that most parents don't have first, second or even third hand experience with these diseases," said Dr. Amanda Dempsey, one of the authors of a new report based on the survey from the University of Michigan in Ann Arbor.
Whether or not to get their kids vaccinated "is more of a theoretical concern or concept for them," Dempsey told Reuters Health.
But, she added, "These are really real risks that are out there. None of these diseases are completely eradicated."
The Centers for Disease Control and Prevention's vaccination schedule for kids six and younger includes MMR (measles, mumps and rubella) shots, and vaccines to protect against whooping cough, chicken pox, hepatitis and seasonal flu, among others.
The internet survey included 748 parents of kids between six months and six years old. Of those, 13 percent said they used some type of vaccination schedule that differed from the CDC recommendations. That included refusing some vaccines or delaying vaccines until kids were oldermostly because parents thought that "seemed safer."
Dempsey said there is no evidence for the safety or effectiveness of such alternative schedules.
In addition, two percent of parents refused any vaccination altogether, according to findings published in Pediatrics.
Even among parents who did follow the recommended schedule, about one-quarter said in the survey that they thought delaying vaccines would be safer or that the expert-backed schedule wasn't the best one to follow.
Dempsey said there's extra concern that those parents will stop getting their kids the recommended vaccines. "It's really quite worrisome to me," she said. Vaccine refusal and delay, she added, "is not likely to go away anytime soon, and is likely to get significantly worse over time. We may just be seeing the tip of the iceberg right now."
Parents who skip or delay vaccines typically cite safety concerns, researchers said, including the now-debunked idea of a link between vaccines and autism. What they miss is the risk of the disease they aren't vaccinating against, said Saad Omer, an infectious diseases researcher at Emory University in Atlanta.
"Parents often have this perception that it's a benign choice, whether to vaccinate or not," Omer, who was not involved in the new research, told Reuters Health.
He said that parents who refuse vaccines tend to cluster together in certain areas, increasing the risk of a local disease outbreak, even in kids who have been vaccinated.
Because no vaccine protects 100 percent of kids who get it, epidemiologists rely on "herd immunity" to make sure enough kids are well enough protected to keep a disease from spreading.
But that immunity gets thrown off when there are more youngsters who haven't had their recommended vaccines.
"Infectious diseases are somewhat unique in a way in that others' behavior directly influences you or your child's risk of disease," Omer said.
He said vaccine refusal already has increased the risk of whooping cough spreading in communities, for example.
"We're seeing schools having to close because of pertussis," Dempsey said, adding that measles cases have also spiked recently.
With some diseases, such as polio, the risk of getting sick in the U.S. even if you aren't vaccinated is pretty low. But, "when a bad outcome happens to your family, it's 100 percent," Dempsey said. "You can't ever say it's not going to be your kid."