These days parents are often more afraid of the immunizations that their children are asked to take than of the diseases they are intended to prevent. These parents believe that their children will be protected from diseases like pertussis, measles or the mumps because of something called “herd immunity”–put simply, because everyone else’s child gets vaccinated it’s unlikely that a child near mine will get any one of these diseases and thus give it to my unvaccinated child. That way, I avoid having to expose my child either to the disease or the risky vaccine.

The most recent research, though, suggests that this logic may be tragically flawed and that these free riding parents who are trying to benefit from the rest of society’s vaccinated kids may in fact end up with sick kids after all. According to the L.A. Times Booster Shots blog, recent research published in Pediatrics found that 11% of all pertussis cases in the entire Kaiser Permanente system were the result of unvaccinated kids.

In short, herd immunity is not enough. The question parents have to ask themselves is: is the fear of vaccine harm greater than the fear of pertussis? Given that it is the most commonly reported vaccine-preventable cause of death for children under the age of 5 years, I would think parents might want to think twice about refusing vaccines when mortality is so easily prevented.

Summer Johnson, PhD