1. The Science of Religious and Philosophical Exemptions
Saad B. Omer, MBBS MPH PhD
Departments of Global Health, Epidemiology, and Pediatrics
Emory University, Schools of Public Health & Medicine
&
Emory Vaccine Center

2. Vaccine Coverage Levels – United States 1962-2007
Combined 4-3-1: Four or more doses of DTP/DTaP/DT, three or more doses of poliovirus vaccine,
and one or more doses of any measles-containing vaccine.
Combined : Four or more doses of DTP/DTaP/DT, three or more doses of poliovirus vaccine,
one or more doses of any measles-containing vaccine, and three or more doses of Haemophilus
influenzae type b vaccine.
Data prior to 1993 were collected by the National Health Interview Survey and represent 2-year-old
children. Data from 1993 are from the National Immunization Survey and represent month-old
children. Different methods were used for the two surveys.
MMWR 2008;57(35);961-66
CDC Pink Book; 2009

3. Evolution of Immunization Program and Prominence of Vaccine Safety
Chen & Hibbs, Pediatr Ann. , 1998

4. School Immunization Requirements
State laws (not federal)
Major role in low rates of vaccine preventable diseases
Exemptions
Medical
Religious
Personal belief (philosophical) exemptions

5. Exemptions to School Immunization Laws
TYPE OF EXEMPTION(S) ALLOWED
Religious & Medical (28)
Medical only (2)
Philosophic, Religious & Medical (21)
updated March 2005

6. Relative Risk of Measles and Pertussis in Exemptors from School Laws
Measles Pertussis
CO ( )
U.S. ( ) 35
Feikin et al. JAMA. 2000;
Salmon et al, JAMA

7. Complexity of Administrative Procedures to Obtain Exemptions & Proportion of Children with Exemptions
Source: Rota et al., AJPH, 2001

8. State Policies Easy process = High exemption rates
Exemption rates associated with individual risk of pertussis & measles
State policies Disease incidence?

9. Associations between State Exemption Policies and Pertussis Incidence, 1986-2004
Unadjusted IRR
(95% CI)
Adjusted IRR
Type of exemption
Only Religious Exemption
Reference
Personal Belief Exemption
2.06 ( )
1.48 ( )
Exemption ease
Difficult
Medium
1.27 ( )
1.35 ( )
Easy
1.90 ( )
1.53 ( )
Adjusting for allowing parental signature for school immunization forms, proportion inside urbanized area, income (11 categories), and education (7 categories)
Omer et al., JAMA, 2006

10. Non-Medical Exemptions by year 1991 - 2003

11. Nonmedical Exemptions for States With Religious Exemptions and With Personal Belief Exemptions
Only Religious Exemptions Permitted
Personal Belief Exemptions Permitted
Exemption Rate
Omer et al., JAMA, 2006
Data updated

12. Nonmedical Exemptions by Ease of Exemption 1991 - 2007
Easy Exemption Policy
Medium Exemption Policy
Difficult Exemption Policy
Omer et al., JAMA, 2006
Data updated

13. WA State Counties’ School Entry Exemption Rates 2006-2007
Omer et al., New Eng Journal of Medicine, 2009

14. Cluster Search
The idea is to divide the plane into zones such that the probability of having an event of interest is the highest inside the zone, compared to outside the zone.
The radius of these windows varies from zero to an upper limit that can be specified

15. P-value
Source: Assunção & Kulldorff

16. Location of Space-time Pertussis Clusters and Distribution of Schools Inside & Outside Spatial Exemptions Clusters
Omer , Enger, Moulton et al., Am. J. Epi., 2008

17. Relative Locations of Pertussis Space-time Clusters & Exemptions Spatial Clusters
Unadjusted OR
3.0 (2.5 – 3.6)
Adjusted OR
2.7 (2.2 – 3.3)
Overlap of Exemptions Clusters with Pertussis Clusters
Omer , Enger, Moulton et al., Am. J. Epi., 2008

18. Locations of Schools Included in Exemption Clusters in California and Massachusetts

19. Incidence Rate Ratios (95% CI)
Incidence Rate Ratios (IRR) of Pertussis in Census Tracts Inside vs. Outside Exemptions Clusters
Incidence Rate Ratios (95% CI)
California
Massachusetts
(n=3950)
(n=7891)
All ages
1.25 ( )
1.21 ( )
Age-group
0-4 yrs
0.95 ( )
5-17 yrs
2.0 ( )
18 yrs or older
1.31 ( )
Bold: p<0.05

20. Course of a Measles Outbreak by Exemption Status Mesa County, Colorado; 1994-1995
Feikin et al., JAMA, 2000

21. MMWR, 2008

22. MMWR, 2008

23. Parents’ Perceptions by Child's Vaccination Status
Salmon , Moulton, Omer et al., AJPH, 2005

24. Characteristics of Unvaccinated (“Zero Dose”) vs
Characteristics of Unvaccinated (“Zero Dose”) vs. Under-vaccinated Children
Unvaccinated children more likely to be:
Male
White
Belong to households with higher income
Married mother with a college education
Live with ≥ 4 children
Smith, Chu , & Baker, Pediatrics, 2004

25. Trust in Sources of Vaccine Information
HCP: Health Care Provider
VIS: vaccine information statements
CAM: Complementary & alternative care provider
DTP: Dissatisfied parents together
Salmon, Moulton, Omer et al. Arch Ped Adol Med, 2005

26. Disease Susceptibility and Severity and Vaccine Safety and Efficacy
Health Care Provides in High Category
Association with Parent Responses
Exempt
Vaccinated
Odds Ratio
Disease Susceptibility
11.3
5.7
1.34
Disease Severity
30.2
29.4
1.36
Vaccine Efficacy
87.0
88.8
1.21
Vaccine Safety
88.9
93.9
3.28*
Were none of thesse statstically significant?
* P Value <0.05
Salmon , Pan, Omer et al., Human Vacc. 2009

27. States with Permanent Only, Temporary Only, and Permanent & Temporary Medical Exemptions –2004-2008
Incidence Rate Ratios of Medical Exemptions by Type of Exemption Permitted
Temporary Only
Reference
Perm. & Temp.
2.17 (0.77, 6.12)
Permanent Only
4.07 (1.17, 14.19)

28. Vaccine Delay Novel vaccine schedules
Consequences not studied in detail
Risk of vaccine preventable diseases is not constant across childhood
Vaccine delays may leave young children vulnerable
Potential exacerbation of health inequities
involve spreading vaccines
Omer et al., New Eng Journal of Medicine, 2009
Offit & Moser, Pediatrics, 2009

29. Conclusions Effective administrative controls
Ease of filing paperwork vs. vaccination
Identification of high-risk geographical areas
Impact of actions of exemptors on overall risk
Engage local stake-holders
Importance of providers
Should states report a clustering statistic?
These findings highlight the impact of state-level policies on pertussis incidence and support the need for effective administrative controls over granting non-medical exemptions. State-level policies on non-medical exemptions and administering immunization requirements should be viewed as part of the efforts to control pertussis and maintain a low incidence of other vaccine preventable diseases.

30. Thank You!