4.2 Literature Exercise

4.2.1 Article Citation

As a reminder, this exercise will be based on a research article with the following citation:

A Randomized, Controlled Trial in Children to Assess the Immunogenicity
and Safety of a Thimerosal-free Trivalent Seasonal Influenza Vaccine (2012).
Domachowske, JB et al., The Pediatric Infectious Disease Journal 31(6): 605.

Read the article and use it to answer the questions that appear below.

4.2.2 Critical Reading

The study examines a thimerosal-free vaccine, where thimerosal is a mercury-containing compound that is hypothesized to increase risk of autism.

What was the primary objective of the study?
- To show that thimerosal in vaccines leads to increased risk of autism
- To show that a thimerosal-free vaccine is noninferior compared to an existing vaccine
- To show that a thimerosal-free vaccine has superior performance to an existing vaccine
What was the explanatory variable and its treatment/factor levels?
- Vaccine amount (varying dosage levels)
- Age of vaccination (three age groups)
- Vaccine type (thimerosal-free vs. existing)
Was a control used? If so, what is the control?
- Yes, the control was a placebo
- Yes, the control was the existing vaccine and contained thimerosal
- Yes, the control was the existing vaccine and did not contain thimerosal
- No, there was no control
What was/were the response variable(s)?
- Adjusted geometric mean titer and seroconversion rates
- Autism rates
- Successful vs. unsuccessful immunization
What is the measurement type for the response variable(s)?
- categorical
- continuous
- neither
Who were the subjects in the study?
- 2116 children between ages 3 and 17
- 2116 adults aged 18 and older
- 2100 children between ages 6 and 35 months
Was the study balanced?
- It was perfectly balanced
- It was close to balanced
- It was very imbalanced
Did the study incorporate blinding? If so, which type of blinding?
- No, the study did not incorporate blinding
- Yes, the study blinded the participant (vaccine recipient) only
- Yes, the study blinded both participants and the study researchers (“double blind”)
Did the study incorporate blocking? If so, what are the blocking variables?
- Yes, they blocked by age, center, prior immunization, and intent to immunize
- Yes, they only blocked by age
- No, they did not incorporate blocking
Was there randomization?
- Yes
- No
- They don’t say
What kind of study was it?
- Case Control Study
- Observational Study
- Randomized Control Clinical Trial
In causal inference notation, what type of study is it?
- Randomized Control Posttest
```
R X O1
R _ O2
```
- Randomized Control Pretest-Posttest
```
R O1 X O2
R O3 _ O4
```
- Soloman 4 Group Design
```
R O1 X O2
R O3 _ O4
R    X O5
R    _ O6
```
What can you conclude from this study?
- The study vaccine causes more harm than the existing vaccine
- The study vaccine is superior to the existing vaccine
- The study vaccine is no worse than the existing vaccine
- The study results were ambiguous