LR Question 10 Explanation, by LSATHacks
QUESTION TEXT: The symptoms of hepatitis A appear no earlier than 60…
QUESTION TYPE: Paradox
FACTS: The vaccine against hepatitis is 100% effective. Yet some people in the group who received the vaccine nonetheless exhibited symptoms of hepatitis A.
The symptoms always take at least 60 days to appear.
ANALYSIS: One possible answer would be that other diseases also cause the same symptoms that hepatitis A causes.
Instead the question requires you to know something about vaccines: they prevent disease but they do not cure it. If you are already infected a vaccine can’t help you. So it could be that the people who exhibited symptoms were already infected. The symptoms take a while to show up.
___________
- The placebo group isn’t puzzling. The strange thing is that people who actually received the vaccine still got sick.
- This shows that the vaccine group received some benefit but it doesn’t explain why there were still some sick people.
- This shouldn’t matter: the vaccine is supposed to work every time. Yet some people got sick.
- CORRECT. The vaccine can’t help you once you have the disease.
- This shows the vaccine might have helped. But it’s supposed to prevent the disease entirely. This doesn’t explain why it didn’t.
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When doing this question, I was suspicious of D as a trap answer because it seemed so straight-forward. Can someone explain why this is correct when it makes no mention of the placebo group? I thought the correct answer would have to address both groups. For me, none of the answers stood out as a correct choice.
Thanks, APRP
We’re trying to resolve the discrepancy between the following facts: a) the vaccine is completely effective at preventing new infections, and b) the group who received the vaccine somehow still exhibited symptoms. (D) provides one possible reason why the group would exhibit symptoms.
The answer choice doesn’t need to address the placebo group since the fact that they exhibited symptoms isn’t surprising. They weren’t immunized against hepatitis A.