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The 'herd' doesn't protect unvaccinated children

May 26, 2009 |  1:29 pm

Vaccine A growing number of parents are declining to have their children immunized for such diseases as polio, diphtheria, measles, mumps, rubella and pertussis. The result is that more outbreaks of these illnesses are emerging and -- surprise -- the children of parents who refuse immunizations are at much greater risk for infection.

A study published today in the journal Pediatrics found that children whose parents declined to have them vaccinated had 23 times the risk of being infected with pertussis compared with vaccinated children.

Parents used to fear these childhood illnesses but today, the authors of the study note, some parents fear the vaccines more than the illnesses. They believe the vaccines overload a child's immune system and may cause dangerous side effects or they simply don't think their child is at risk for the diseases.

The study, by researchers at Kaiser Permanente Colorado and Johns Hopkins Bloomberg School of Public Health, analyzed data from children in the Kaiser Permanente health plan in Colorado from 1996 to 2007. Each case of pertussis was matched with four randomly selected control cases. The study found that in the entire Kaiser Permanente population, 11% of all pertussis cases were attributed to parents' refusal to have their children vaccinated.

Even though most children are vaccinated, there isn't enough protection in the population -- called the herd immunity effect -- to protect unvaccinated children from contracting the illness, the authors say. "This result dispels one of the commonly held beliefs among vaccine-refusing parents that their children are not at risk for vaccine-preventable diseases," they wrote.

The authors note that parents who are inclined to skip recommended vaccinations should receive information about their children's risk of getting the disease. The American Academy of Pediatrics has a position paper on the topic entitled, "Responding to Parental Refusals of Immunization of Children."

-- Shari Roan

Photo: Tim Boyle / Getty Images