96% Herd Immunity at Walden School

September 18, 2014

Some journalists are erroneously using data that was pulled from the State of California Department of Health Services to report a skewed view of “herd immunity” at Walden School. The cited data is a snapshot of one report from the first month of school in 2013. With thousands of schools in California, it is an inefficient reporting system and many journalists are not reporting the full picture of what constitutes “herd immunity” at our school.


The form filed in 2013, unfortunately, did not distinguish between delayed vaccinations (temporary PBE) and no vaccinations (permanent PBE). By publishing that in September 2013, 42% of Kindergarteners (or twelve out of 28 students) at Walden School were not vaccinated, journalists mislead readers because within a few weeks that number radically dropped to 3% as children’s 5-year wellness visits were completed and vaccinations were updated. Only one student out of 28 kindergarteners last year filed a permanent Personal Beliefs Exemption (PBE).


Vaccinations delayed by a few weeks after the start of the school year (because a child has not yet turned 5 years old) is not the same as delayed vaccinations for personal/religious beliefs (temporary PBE). Different again is the permanent Personal Beliefs Exemption (PBE) which means that parents have opted out of all vaccinations for their child. Because Walden School does not have a birthday cut-off date, some of our students complete their 5-year wellness checks after the first day of school.


Since children are born on different days of the year, there is no magic one day when herd immunity can be codified for all schools. Probably for ease of collection, the State asks schools to report stats each fall on the incoming Kindergarten class for that year on the first day of school. But even that is not accurate, as different schools have different start dates.


Herd immunity is established over time and the data used in this recent news cycle does not accurately portray actual community immunity at Walden School (and probably is misleading for other schools, too, due to the inefficiency of the State reporting system). In recent school years, across our entire student body, between 94 -96% of students have met all vaccination requirements and/or documented history of disease. The CDC and the World Health Organization have estimated herd immunity thresholds for vaccine-preventable diseases in ranges from 75-94% depending on the specific contagious disease.


In January 2014, a new form was developed by the State and this fall’s report filed by all schools addresses some of the data collection issues. The form Walden School filed this September distinguishes the number of kindergarteners with all required immunizations and/or documented history of disease from the number of kindergarteners exempted from any immunizations due to Permanent Medical Exemptions (PME), or Personal Beliefs Exemptions (PBE). These students are counted as Unconditional Entrants.


Students with a PBE are further quantified between “Pre-January 2014” exemptions, “Health Care Practitioner Counseled” exemptions, and “Religious Exemptions.” Two students filed a PBE this year (out of 29 students in Kindergarten).


Conditional entrants are also documented on this year’s form. These are students who have a temporary medical exemption because they have not yet met all of the required immunizations but are on a delayed vaccination schedule and these kindergarteners require follow up documentation.


The State of California Department of Health Services advises that in case of an outbreak of any one of the diseases for which a child is not vaccinated, that child may be temporarily excluded from attending school for his/her protection.


Like any other health concerns you have about your child, consult your health care professional about what is best for your child with regards to vaccinations.

One Response to “96% Herd Immunity at Walden School”

  1. barbarafromburbank Says:

    Thank you for the information and thank you to all the parents!

    Calum’s Grandmother

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