Half of U.S. babies may miss on-time vaccinations

Delayed immunization could boost disease risk

As the resistance to vaccines that emerged in the public consciousness a decade ago appears to subside, another public health problem is emerging in the form of delayed vaccination. A new study suggests that half of U.S. babies don’t get routine vaccinations on time, some of them because parents put off the shots. The delay rate has climbed since 2004, researchers report January 21 in JAMA Pediatrics.

Scientists reviewed  medical records and found that one-eighth of these delays were intentional as parents defied immunization schedules set out by health authorities. Other parents may have inadvertently missed vaccinations or had lapses in insurance coverage, the study authors say.  

Some parents see the bunching of recommended vaccinations as risky and try to space out their children’s shots, says study coauthor Jason Glanz, an epidemiologist at the Institute for Health Research at Kaiser Permanente in Denver. Delays in vaccination, sometimes called alternative scheduling, might appeal to those parents since babies are scheduled to get 23 shots during the first two years of life. “You can see the parents’ perspective in saying that’s a lot,” Glanz says. But delays pose risks, he says, since the shots prevent diphtheria, tetanus, pertussis, hepatitis, measles, mumps, rubella, polio, rotavirus, pneumonia, meningitis and chickenpox.

Edgar Marcuse, a physician at the University of Washington School of Medicine in Seattle, says timely immunization is important precisely because many of these diseases occur in the first years of life. There is no credible, science-based evidence to suggest that putting off vaccines protects children, he says. “Spacing out the vaccines delays protection, increases the risk that some vaccines will be omitted and increases the cost by requiring multiple visits without yielding any demonstrated benefit.”

Glanz and his colleagues analyzed the vaccination histories of 320,000 children 2 to 24 months of age in eight managed-care organizations across the United States. The researchers considered the shots to be on time if they came within a one-month grace period of the schedule. For a vaccination or booster due at 6 months, for example, a parent had until the 7-month point before the child would be listed in the records as delayed for that shot. Even with that buffer, 49 percent of children were late for at least one vaccination, the records show. Of babies late on vaccinations, 20 percent logged more than 100 days in which they were unprotected from a disease, the records show.

When the researchers looked at three common vaccines, they found that all three showed substantially more first-shot delays in 2008 than in 2004.

Children who had delayed vaccinations had fewer outpatient clinic visits but 20 to 30 percent more hospitalizations than did kids who were vaccinated on time, Glanz says. Kids whose parents delayed their vaccination intentionally were less likely to make outpatient visits to clinics or go to an emergency department than those vaccinated on time. The reason is unclear, Glanz says, but such parents might be less likely to seek standard medical care.

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