ATS1262 Lecture Notes - Lecture 2: Inter-Rater Reliability, External Validity, Demand Characteristics
Document Summary
Get access
Related Documents
Related Questions
The Scientific Method
For any controlled scientific study, a scientist starts with an observation, does some research to develop a hypothesis, and then designs an experiment that compares some baseline group with a test group. Data are then collected to confirm or refute the hypothesis.
As you review the following study, consider whether the researchers correctly followed the scientific method.
In the late 1990s, gastroenterologist Andrew Wakefield, along with a research team, set out to determine if bowel disease caused by vaccines led to autism.
He compiled a group of 12 children who had loss of acquired skills, developmental delays in language, diarrhea, and abdominal pain-essentially, those with both bowel disease and autism. He questioned each parent about the behavior and personality of the child before the child was vaccinated with the Measles, Mumps, and Rubella (MMR) vaccine. He then ran tests on the children to determine the health of the gastrointestinal tract, brain, and nervous system.
His reported data (tabulated below) included that children experienced either gastrointestinal or autism-like symptoms, sometimes within a short period after being vaccinated. From these data, the researchers concluded that there was no link between autism and the MMR vaccine. Wakefield though, contradicted this conclusion and stated that the vaccine caused changes in the gastrointestinal tract of the children, which then led to autism (Wakefield, et al., 1998). Currently, he still contends that the MMR vaccine contributes to autism (Ziv, 2015).
Many researchers tried to duplicate this study and could not replicate Wakefield's results. In fact, they found no link between the vaccines, bowel disease, and autism. In the United Kingdom, the MMR vaccine was not introduced until 1988. If Wakefield's conclusions were correct, one would then expect a jump in autism cases after 1988, but this was not observed, even when hundreds of children were studied (Taylor et al., 1999). In these additional studies, children who had not been vaccinated were included as a control group, and no difference in the rates of autism was observed.
In 2011, Brian Deer reviewed Wakefield's study and all available records from the National Health Service (NHS) in the United Kingdom for these 12 children. He found that at most, two children showed symptoms days after vaccinations. At least five children showed developmental delays before being vaccinated. Six out of the 12 children may have had autism symptoms. None of the 12 children tested had all three-regressive autism, colitis, and symptoms days after vaccination.
| Symptom | Wakefield | Wakefield NHS Records |
| Symptoms days after vaccination | 8 | 2? |
| Non-specific colitis | 12 | 3 |
| Regressive autism | 9 | 6? |
| Intestinal/autism/symptoms after vaccine | 12 | 0 |
(Wakefield, et al., 1998; Deer, 2011)
Wakefield's statements led to a worldwide panic about the safety of vaccines, but after Deer's report, Wakefield's study was retracted and his medical license was revoked for falsifying data. Click on the following links to review materials to enhance your knowledge of the scientific method and to support your analysis of Wakefield's experiment:
Steps of the Scientific Method: A simplified explanation of how the scientific method works, the steps taken to investigate phenomenon with diagrams
Do Vaccines Cause Autism?: A review of research demonstrating that vaccines and their components are not the cause of autism
Fifteen years after a vaccine scare, a measles epidemic: An analysis of vaccination trends and an increase in measles cases seen the UK
Answer the following 4 questions:
What was wrong with Wakefield's study? Discuss at least 1 variable or approach that should have been controlled or assessed.
Consider the source of some of his data (parental memory, for example), the small sample size, and whether he considered other variables (genetics, diet, and so on) that could have resulted in symptoms in these children.
Discuss the importance of a control group when using the scientific method.
Did Wakefield deserve to be barred from medical practice?
What were the consequences of his inflated conclusions?