Health Column: Childhood vaccines & herd immunity |

Health Column: Childhood vaccines & herd immunity

Phil Mohler, M.D.
Free Press Health Columnist

Wingate Elementary School, 84.7 percent; Juniper Ridge Community School, 63.5 percent; Mesa Valley Community School, 62.7 percent: These are not Partnership for Assessment of Readiness for College and Careers (PARRC) testing participation, but the percent of kids in these Grand Valley schools that are up to date on their basic immunizations. This data is alarming.


In a population where a high percentage of Individuals are immune to a disease (either through having had the illness or immunization), chains of infection are likely disrupted, slowing or stopping the spread of the disease. The greater the proportion of individuals in a community who are immune to a disease, the less likely that an individual who is susceptible will come in contact with an infected individual. This is called “herd immunity.”

Diseases have different thresholds for herd immunity. In a recently published study in JAMA Pediatrics, the authors concluded that at least 96 percent of a population needs to be immune to measles to provide herd immunity. That means in a given population, if more than one in 25 individuals is susceptible to measles, the disease will continue to spread. Measles is the poster child for spread of disease as it is easily transmitted via droplets from coughs.

Why have childhood immunization rates fallen in the last decade? Paradoxically, the major reason is that pediatric immunizations have worked too well. In 2000, measles was declared eradicated from the US. The perceived risk of getting the measles plummeted.

Secondly, a British physician published a paper that associated childhood vaccines and autism. Although the causal relationship has been thoroughly disproved, the study withdrawn and the doc de-licensed, the faulty myth has persisted, championed by playboy playmate Jenny McCarty, who also believes that Google is a university.

Finally, Colorado is home to one of the easiest “opt out” personal vaccine exemption policies in the country. One signature on one piece of paper once and your kindergartner is exempted from all immunizations through high school. It is understandable why well-meaning parents opt their kids out! The childhood vaccine schedule is a nightmare ­— over 60 vaccine doses over nine or 10 visits by age 6. Reluctant kids, waiting, waiting to be seen, travel, keeping track of vaccines — all this makes opting out look really good.

Reality Check: The current routine childhood immunization schedule is estimated to prevent 42,000 deaths and 20 million cases of disease and to save $14 billion in direct medical costs annually.


Vaccines are safe. One of my pediatric colleagues points out to parents that their drive to the office carries more risk than any childhood immunization.

The vaccine personal exemption law in Colorado needs to be much more rigorous. There is abundant data that shows states that have “easy opt out” laws have lower rates of immunization and much higher rates of vaccine preventable disease. There are good models of tougher standards, including requiring counseling, explaining the benefits of vaccines and requiring parents to sign a statement stating the reasons for opting out.

When do public health priorities trump our individual rights?

Free Press health columnist Dr. Mohler has practiced family medicine in Grand Junction for 39 years. He has a particular interest in pharmaceutical education. Phil works part-time for Rocky Mountain Health Plans. Email him at

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