1. Fence Sitters: What do we know about those considering exemption?
Martha Priedeman Skiles, MPH,
Steve Robison, BS, Collette M. Young, PhD, James A. Gaudino, MD, MPH
Oregon Public Health Division
Immunization Program
Today my presentation focuses on one of our analyses from a large survey of parents of school-aged children in Oregon.
I’d like to acknowledge my co-authors:
Steve Robison
Collette Young
James Gaudino

2. Background
Oregon School requirements include: DT, Polio, MMR, HepB, Hib, and Varicella
Religious exemptions, by law are allowed for any system of beliefs, practices, or ethical values.
A religious exemption may be for 1 or more than 1 required vaccine
Religious exemptions are rising in Oregon:
2.8% SY03/04
3.4% SY04/05
3.5% SY05/06
Oregon’s school exclusion process is different then most states. Issuing exclusion orders and excluding children falls under the authority of the local health department who work in partnership with the schools.

3. Purpose
Determine what specific factors may influence a parent from considering an exemption to actually signing an exemption

4. Study Methods
Case-control study of 2,900 students (K-5), randomly selected from public and private schools statewide
Population-proportionate sample from high school based communities stratified by exemption rate and location
43-question mail survey with telephone follow-up as needed
Exemptors (Cases) and Fully Vaccinated (Controls) were sampled on a 1:3 ratio. Response rate varied slightly between cases and controls, resulting in a 1:2.5 ratio.
High-school based communities were stratified by exemption rate (high, medium, or low exemption rates) and geography (urban, rural). Elementary schools were randomly selected from each stratification, with a list of back-up schools to select from as needed. Parents of children within selected elementary schools had an equal chance of selection based on whether any child in the household had an exemption on file with the school.
Households first received an opt-out postcard, followed by an introductory postcard with option to answer on the web, followed by 2 survey mailings and phone follow-up on non-responders. ~54 households opted-out.

5. Study Methods Adjusted response rate = 55%,
323 exemptors, 1265 non-exemptors
Post-stratified weighting on educational status to adjust for non-response
Stata 9.2 used for weighting and multivariate logistic regression models
Following is preliminary analyses of a sub-population – exemptors and considereds
Complete randomization at each level of stratification limited our need for extensive post-stratification weighting.

6. To exempt or vaccinate 80% (76-85%CI) vaccinated without considering
an exemption
14% (12-16%CI) vaccinated
but considered
an exemption
Three groups studied based on survey response to question:
Have you ever considered getting an exemption from vaccinations for your child?
No - vaccinated child without consideration of an exemption
Yes – considered an exemption but went ahead with all vaccinations
Yes – child has an exemption
6% (5-8%CI)
signed an exemption

7. Respondent Demographics
Age % (26-35 yr olds)
Income < 25K % (Vaccinated)
15% (Considered)
32%** (Exempt)
≥ 3 Kids % (Vaccinated)
20% (Considered)
30%* (Exempt)
Age was normally distributed across each group.
All income categories were also normally distributed, except for those reporting < $25K annual income.
Exemptors were slightly more likely to report having more children.
** p<.05, * p=.05 between Considered and Exemptor

8. Child’s Healthcare Provider
Vaccinated, Vaccinated,
no exemption considered Exempt
considered exemption
Allopathic
100%
Allopathic
100%
Allopathic
93%
Allopathic providers = MD, DO – pediatrician, family practitioner, general practitioner, county health department
Alternative providers = Naturopath, Chiropractor, homeopath, acupuncturist, etc
100% of the fully vaccinated, whether they considered or not, saw an allopathic provider with a small percentage also seeing an alternative provider.
Over 1/3 of the exemptors sought care from an alternative provider. Of the 28 children who only saw alternative providers; 26 of them got exemptions.
Alternative
38%
Alternative 3%
Alternative
15%

9. Beliefs about Vaccines
Seven questions addressing beliefs about vaccines and vaccine-preventable diseases were asked. Each question was ranked on a 5 point likert scale from Strongly Agree to Strongly Disagree.
These are an example of the questions and responses. The test of significance was between the Exemptors and the Vaccinated (vax + considereds)
Note that approximately 50% of the Considereds and Exemptors agreed that “vaccines sometimes cause autism”
* p<.01 between Fully Vaccinated and Exemptors

10. Scale: Beliefs about Vaccines
A scale of beliefs was created for the model, grouping respondents by an aggregate score on the 7 belief questions.
Full scale: -14 to +14
Anti-Vaccine Sentiment = -14 to -5
Neutral = -4 to 4
Pro-Vaccine Sentiment = 5 to 14
Exemptors were much more likely to have negative vaccine sentiments
**p<.001, *p< .05 between Considerers and Exemptors

11. Trusted Sources of Info
A series of questions addressed which sources parents trusted for health care information. Those listed are the ones with a significant response difference between exemptors and fully vaccinated (vax+considereds).
Only healthcare provider was a significant trusted source of information between Considerers and Exemptors.
* p<.05, ** p<.01 between Fully vaccinated and Exemptors

12. Influences on decision to consider or exempt
A series of questions were asked only of those who stated they had considered signing or did sign an exemption:
What influenced your decision to exempt or not?
Faith = 7%
Provider recommended an exemption = 14%
School promoted or was more convenient = 16%
Anti-State sentiment = 23%
Anti-Vaccine sentiment = 28%
Friends or Family advice = 32%
Distrust of vaccine makers = 47%
** p<.005, * p<.05 between Considerers and Exemptors

13. Factors associated with Signing an Exemption compared to Considering
Variable OR
(CI)
Child sees Alternative Provider
2.45**
(1.29 – 4.67)
Parent holds pro-vaccine beliefs
0.32**
(0.15 – 0.68)
Parent holds anti-vaccine beliefs
3.25**
(1.51 – 6.98)
School promoted or made exemptions more convenient
5.29**
(2.23 – 12.51)
Provider recommended getting an exemption
3.10*
(1.26 – 7.63)
Annual household income < $25K
4.66**
(2.01 – 10.78)
These variables remained in the model with significant effect.
Healthcare provider as a trusted source of information dropped out of the model, as did number of children and “faith” as an influence in the exemption decision.
Income needs to be looked at more closely in combination with a collection of demographics such as employment and number of people the income supports.
** p<.005, * p<.05

14. Conclusions
The relationship between vaccinated, considereds and exemptors is not linear.
Providers remain influential, however the message may vary with medical philosophy.
We’re finding distinct clusters of parents with diverse beliefs and motivations, rather than polar groupings of exemptors as strictly anti-vaccine or convenience exemptors.
More analysis is needed to better describe these influences in order to design strategies to reach these parents with effective messages.

15. Strengths and Limitations
Statewide sampling of schools and parents
Survey methods varied to accommodate school requests
Rich data on community influences
Population-proportionate sampling stratified by community exemption rate
Some school districts chose not to participate, however at the beginning we established a list of sample schools and back-up schools based on rate and geography. We were able to select replacement schools from those backups.
Some schools agreed to participate only if they could handle the parent mailings, so follow-up was limited with non-responders from those schools.
Individual definition of community and possible influence of community norms are pretty complex. Additional analyses will help us untangle that.

16. Acknowledgments Funding provided by CDC grant 1 UO1 IP000031-01
Survey conducted by the Social & Economic Sciences Research Center at Washington State University.
Contact: Martha Priedeman Skiles
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