Vaccinations and Catholic Exemptions: Impact Report

Vaccinations and Catholic Exemptions
Exploring the Impact (February 2006)

A study has been prepared to determine what sort of outcome a united effort by Catholic authority might have on the health of the population by pressuring the Federal Government and Pharmaceutical Industry for ethical alternatives to aborted fetal vaccines. The information focuses on the possibility of greater numbers abstaining from these vaccines for their families as a result of public knowledge of that effort.  The obvious goal is to achieve the desired objective without impacting the health of the population.

In determining thresholds for controlling disease among a population, many factors are taken into consideration, including:

  • Population in a given geographic area
  • Environment
  • Health conditions
  • Rate of infection of various diseases
  • Waning immunity in vaccinated children
  • Vaccine failure rate
  • The segment of the population with contraindications to vaccination.

Herd immunity, or herd “effect” is the ability to stop the spread of disease based on a proportion of subjects with immunity in a given population. Note that the more contagious a disease, the higher the percentage of immune persons required to “break transmission”, or to achieve effective herd immunity.

Further, the number of people who are immune is made up of both those who contract the disease naturally and those who have been vaccinated. That is, the proportion vaccinated does not equal the proportion immune.Once the proportion of the population that is immune exceeds the herd immunity level for the disease, then the disease can no longer present serious problems in the population.

Virologists and epidemiologists who have studied these areas have found that when a certain percentage of a population is vaccinated, the spread of the disease is effectively stopped. Taking all data into consideration, the Centers for Disease Control (CDC) along with the World Health Organization (WHO) has established desired thresholds for various diseases.  The thresholds for just some of the diseases are shown below. In this report we will focus on maintaining rubella protection among the population since this is the area of greatest concern.

Herd Immunity Thresholds By Disease – Examples

Source: and
feb_concepts (Epidemiology Centers for Infectious Disease Preparedness)

Disease Level of Herd Immunity Required
(Percentage of Population Immune)
Influenza  75%
Chickenpox 80%
Diphtheria  85%
Measles 83-94%
Mumps 75-86%
Rubella: 83-85%

NOTE: Herd Immunity levels as shown include vaccinated children and those with natural immunity. While there is a wide variance in these thresholds needed by disease, 90% is an average factor used.

The following figures depict current levels of vaccination and how religious exemptions might impact the population within both the Catholic School systems and the Public Schools. Other reasons that make up the unvaccinated population may be medical or philosophical, but we will only focus on the religious aspect.

Current Vaccination Levels Among All Schools


Coverage Estimates for School Entry Vaccinations

2002-2005 School Years  – United States


Coverage %


Coverage %


Coverage %






















 Hep B








Children Enrolled in K-12 Schools – Percentage With Religious Exemptions on a national average is less than 1%.

US Catholic Population

U.S. Data







Catholic population

45.6 m

48.7 m

52.3 m

57.4 m

59.9 m

64.8 m

Percent of U.S. population







Catholic elementary schools




Students in Catholic elementary schools





If the number of new enrollments began exempting at the rate of over 30% rather than the actual figure of < 1%, the herd immunity levels would fall to 88.9%, which is below the recommended level of 90% but still fall well above the 83-85% CDC herd immunity levels required.

However, such a decreased level would most likely never occur for a number of reasons:

  1. The majority of the population is unaware of the aborted fetal vaccine issue
  2. Among those who do know, most of those entering school have already been vaccinated at least once and thus 95% (vaccine efficacy rate) will have rubella immunity. (One dose of rubella provides immunity; MMR booster is only required due to measles vaccine inadequacy -CDC MMWR, May 22, 1978, Vol 47, No. RR-8, Documentation of Immunity, Pg 10)
  3. Among those who do know, a large portion are still vaccinating
  4. Rubella No Longer A Public Health Threat in the United States, announced by the Centers for Disease Control Director, March 21, 2005. Director Julie Gerberbing revealed that both rubella and CRS had been eliminated in the US with less than 10 cases of rubella per year for the past 3 years and only one case of CRS.   These outbreaks were among adult immigrants, not US native-born cases and they were self-contained.  No children were involved and no other persons were infected.
  5. The study assumed all students in parochial schools are Catholic, thus the 88% immunity level would actually be higher.  According to the NCEA, the percentage of non-Catholics in Catholic schools is 13.6%

The study then examined how Catholics could affect the health of students in public schools. Because the number of Catholics to the general population is so small, even with 50% of the Catholic population exempting, the immunity level remained at 94%.  Taking this one step further, if all Catholics exempted, along with the < 1% average of the rest of non-Catholic students, plus all those exempting for other reasons, the level of herd immunity would remain substantially high at 91.8%

Long Term

Since there was no point in studying the impact any further in public schools, the research then examined what long term affect the exemptions might have on the population in the Catholic schools. The objective was to determine if immunity levels would fall into risk as the 8th grade level left the elementary school population with new Preschool children entering and exempting in higher numbers.

The study ignored the fact that Catholic enrollment has decreased over the past five years according to the NCEA records. Instead, using figures from the US Census Bureau, they increased the number of new enrollees at the national growth rate of .92%.

Further, the study intentionally ignored the fact that 13.6% of the new and existing enrollment is non-Catholic and therefore that percentage would not be increasing exemptions. They instead used an increase in exemptions to 5% over the existing figure of < 1%.

After 5 full years the school year, the herd immunity would still be at 94%

One reason for the negligible decline in herd immunity levels may be due to a smaller population entering the school system than the population leaving in 8th grade and a growing trend of more traditional Catholics home-schooling their children. Since that has remained consistently true for the past 5 years according to NCEA data, we assume the trend will continue.

In summary as shown in previous secular reports, religious exemptions have not had any significant impact on outbreaks in the United States. That is not to say they couldn’t, however both historically and through the study conducted, it is unlikely based on current health conditions and immunity levels. If a group of students are exempting for religious reasons, the only risk they pose is within their own group and certainly not among other vaccinated children and staff. Should an outbreak occur, the State Health departments work with the Centers for Disease Control to determine appropriate action. Normally, non-vaccinated children are sent home until the crisis passes so as to protect them and control further spread of the disease.  Unless the outbreak occurs when school enrollment is beginning, admission is never denied to students with any type of exemption.  However, even if the students must be temporarily denied admittance due to an outbreak, they are then allowed admittance after the disease in question has been contained.

In addition, it is worth noting that Catholics make up approximately 23% of the population whereas other denominations exempting for religious reasons encompass 77% of the existing < 1% average, therefore the Catholic population will always have a significantly lower impact on religious exemptions in the general population.

Further, the remaining percentage of non-vaccinated students (2.85%) have a greater chance of infecting the population than the percentage with either Catholic or non-Catholic religious exemptions.