CHICAGO — Parents have increasingly pressured doctors to delay vaccines for young children, making their kids and others vulnerable to preventable diseases, a study suggests.

The findings are in a national survey of pediatricians and family doctors asked about parents wanting to postpone some of the many shots recommended for children younger than age 2. Nearly all doctors said that at least some parents had requested vaccine delays in a typical month; and 1 in 4 said those numbers had increased since the previous year.

More about the survey in Monday’s Pediatrics and delaying childhood vaccines:

The study

The researchers surveyed 534 doctors by email or regular mail in 2012. Participants were doctors who are members of the American Academy of Pediatrics and the American Academy of Family Physicians — the two leading groups of doctors who treat young children. One in 5 doctors said at least 10 percent of parents had requested vaccine delays by spreading them out over more months than is recommended.

Most doctors said the practice puts kids at risk for getting vaccine-preventable diseases and might lead to disease outbreaks, but most also said they at least sometimes agreed to the delays. Only 3 percent said they often or always tell parents who insist on vaccine delays to seek care from another doctor.

The concerns

The potential repercussions are worrisome and are happening “right now with the measles outbreak,” said Dr. Allison Kempe, a University of Colorado researcher and a member of the federal Centers for Disease Control and Prevention’s vaccine advisory committee. More than 150 people in several states have been infected with measles, including infants too young to be vaccinated. Most cases are tied to an outbreak at Disneyland in California, which likely began with a traveler who brought it in, as has been the case in other U.S. outbreaks. The exact source of the Disneyland-linked cases is not known.

Doctors are concerned about unvaccinated or under-vaccinated children becoming ill and spreading disease to others.