Using the information provided in the case study, complete Sections B, C, and D (pp. 5-10), typing your answers into a separate document.

Section B: Calculating Measures of Association

Over 25 studies have been conducted which have failed to show an association between MMR vaccine and autism. Below are some data from two of these studies (one cohort and one case-control). Calculate the measure of association for each study after completing the 2x2 table and interpret the measure of association.

1. Cohort study by Madsen et al (NEJM 2002) Of the 537,303 children in the cohort, 440,655 (82.0 percent) had received the MMR vaccine. We identified 316 children with a diagnosis of autistic disorder; 263 of the cases had been vaccinated with MMR (83%); 53 children with autism had not been vaccinated.

 263/440,655 = 0.00059684*100 = 0.059%

 53/96,648 = 0.00054838*100 = 0.054%

Relative risk = 0.059/0.053= 0.11. If RR<1

Atributable risk (AR)

Incidence of autism among vaccinated children : 263/440,655

Incidence of autism among unvaccinated children: 53/96,595

0.000596 -0.000548 = 0.000048 or 0.048 autism cases per 1000 people per year. The proportion of cases due to vaccine administration is not relevant.

Calculating the Relative risk and comparing the incidence of Autism with those not exposed to the MMR vaccine, the incidence of disease over the incidence of the exposed includingall in the denominator for each group.

The Exposed children were 0.11 (RR = 1: no evidence of association or RR >1 : exposure is harmfull) which demonstrates that the strength of the relationship is weak and there is no level of association between children that received the vaccine compared with those that did not receive the vaccine.

The likehood of an of children that received the MMP vaccine with a o.o1 ratio compared to the group that did not received the MMR vaccine is weak.

2. Case control study by Smeeth et al (Lancet 2004)

1294 cases of pervasive developmental disorder (PDD) and 4469 controls were included. 1010 cases (78.1%) had MMR vaccination recorded before diagnosis, compared with 3671 controls (82.1%) before the age at which their matched case was diagnosed.

   a*d = 1010*798

   b*c = 3671*284

   = 805980/1'042,564 = 0.77

Total                                     1294            4469               5763

The Odds Ratio (OR) included children that already had the disease and measured the association or the Odd Ratio aproximating the Relative Risk (RR).

Section C: Interpreting results Review the following data from the aforementioned studies and answer the following questions. FIGURE 1: Table 1 from Madsen et al.,

FIGURE I: Table 1 from Madsen et al., 2002

TABLE 1. CHARACTERISTICS 01: 'HIE 537,303 Cutt.os.P.N IX 1111‘: DANISH COHORT.

1. Describe the characteristics in Table 1 in terms of what type of data they are (discrete / qualitative versus continuous/quantitative).

Using the chi-square test (see footnote of FIGURE 1), authors found significant differences in certain characteristics of vaccinated and unvaccinated children.

2. What characteristics showed no differences between the two groups? What characteristics showed differences between the vaccinated and unvaccinated groups?

3. What do these differences mean?

FIGURE 2: Fable 2 from Madsen et al., 2002

The New England Journal of Medicine
TABLE 2. ADJUSTED RELATIVE RISK OF AUTISTIC DISORDER AND OF OTHER AUTIST1C-SPECTRUM
DISORDERS IN VACCINATED AND UNVACCINATED CHILDREN.*

4. Do the data in Figure 2 above show an association between MMR vaccine and risk of autism?

FIGURE 3: : Tables 1 and 2 from Smeeth et al 2004

Table 1: Association between Pervasive Developmental Disorder (PDD) and MMR vaccination before index date, before and after third birthday, and before and after age 18 months.

UK General Practice Research Database (GPRD)

5. Do the data in Figure 3 from Smeeth et al show an association between MMR vaccine and risk of autism?

Section D: Conclusion

Since 1998, numerous well-designed studies have found no link between vaccines and autism (see table below). Why do you think some parents are still fearful of vaccines? What is your role as future healthcare providers in counseling patients about vaccines?

Table 1. Studies that fail to support an association between measles-mumps-rubella vaccine and autism.

References

Madsen KM et al. A population-based study of measles-mumps-rubella vaccination and autism. N Engl J Med 2002;347(19)1477-82. Retrieved from http://www.nejm.org/doi/full/10.1056/NEJMoa021134#t=articleMethods

Offit, PA. & Coffin, SE. Communicating science to the public: MMR vaccine and autism: Vaccine 2003: 22(1) 1-6.

Smeeth L et al. MMR vaccination and pervasive developmental disorders: a case-control study. Lancet 2004;364:963-9.

Simeonsson, K., Bethel, J., & Lea, S. (n.d.). Weighing the evidence: Misconceptions about measles-mumps-rubella (MMR) vaccine and autism.

Retrieved from Association for Prevention Teaching and Research website:

http://c.ymcdn.com/sites/www.aptrweb.org/resource/resmgr/prevention_modules/module_2_student_case.pdf

Using the information provided in the case study, complete Sections B, C, and D (pp. 5-10), typing your answers into a separate document.