STUDENT CASE STUDY, PART TWO B: TIME TREND ANALYSIS―SINGER-FREEMAN
MMR VACCINE AND AUTISM: SCIENTIFIC INQUIRY, ETHICS, AND EVIDENCEBASED PROBLEM SOLVING
CASE STUDY FOR THE AACU STIRS PROGRAM
Karen Singer-Freeman, Associate Professor of Psychology, Purchase College, State University
of New York
STUDENT CASE
Part Two B: Time Trend Analysis
How Can We Study the Effects of Potentially Dangerous Treatments? Methods Used in the Study
of Vaccines and Autism
Time Trend Analysis
If the MMR vaccine causes autism we would expect that the vaccine must be given before the
first symptoms of autism were present. We would also expect that increases in the MMR
vaccination rate (the percentage of children who have received a vaccine) in a geographical
area would be associated with increases in the prevalence of autism in this area. In a time trend
analysis we examine changes in the prevalence of the MMR vaccine and the rates of autism in a
country over time. Many experts believe that rates of autism are rising (Hertz-Picciotto and
Delwiche 2009; Ouellette-Kuntz et al. 2014). If autism is caused by the MMR vaccine then we
would expect the rates of autism to increase as MMR vaccine use increased.
Key Questions
33)
In a time trend study, what result would allow you to conclude that MMR vaccination is
associated with rising rates of autism?
34)
If we observed that the numbers of autism diagnoses did rise with increasing MMR
vaccinations, are there any alternative explanations for these data, aside from the
explanation that the MMR vaccine is causing autism?
A Real Time Trend Analysis
Kaye, Melero-Montes, and Jick (2001) collected information from the United Kingdom general
practice research database to determine the number of children diagnosed with autism
between 1988 and 1999. During this time period MMR vaccination rates were consistently high
(around 95 percent). They found that over the 11 years of their study diagnoses of autism
increased sevenfold. Increases were especially high for boys. The results of their study are
shown in Figure 10.
STUDENT CASE STUDY, PART TWO B: TIME TREND ANALYSIS―SINGER-FREEMAN
Figure 1. Data from Kay, Melero-Montes, and Jick (2001).
Retrieved from http://www.bmj.com/content/322/7284/460. Reproduced from British Journal of Medicine, James A Kaye,
Maria del Mar Melero-Montes, and Hershel Jick, 322:460-463, 2001, with permission from BMJ Publishing Group Ltd.
Key Questions
35)
For children born in 1988, approximately how many out of 10,000 developed autism
(look on the left side of the graph)?
36)
For children born in 1993, approximately how many out of 10,000 developed autism?
37)
What were the vaccination rates during each of these years (look on the right side of the
graph)?
38)
What would you conclude from these results?
39)
Propose another way to study the relation between the MMR vaccine and the
development of autism. Be sure to include the group or groups you would study, the
information you would gather, and how this study would add to our understanding of
vaccine safety.
Once your group is done with these questions, please see your instructor for guidance on next
steps.