Q10 - The symptoms of hepatitis A

[jpchris3]

Hi,

I was wondering if someone could help explain why (D) is wrong and why (E) is correct... I'm a bit confused also about the general discrepancy in the problem.

Thanks!

[ManhattanPrepLSAT1]

Good news! You must have misread the answer key. Answer choice (D) is correct. For others who are looking for an explanation on this one though...

This is a paradox question and we need to explain the discrepancy. First, we need to decide what the discrepancy is. The stimulus states that people who received the hepatitis A vaccine eventually displayed symptoms of hepatitis A. It also states that the hepatitis A vaccine is completely effective in preventing infection. The question is, how can both of these statements be true. There are several ways to explain this. For instance, maybe one can display symptoms of hepatitis A without actually having hepatitis A. It could be a symptom - such as severe fatigue - common to other ailments.

The correct answer takes another route. It states that the people who displayed the symptoms of hepatitis A contracted hepatitis A before they received the vaccine. That would allow for the vaccine to still be completely effective.

(A) is relevant but is the negation of something that might help explain the discrepant findings.
(B) is irrelevant.
(C) is irrelevant.
(E) is irrelevant.

[esnanees]

Hmmmm- I still do not get this argument.I ruled out all the ans choice My understanding is that people with the placebo doesn't produce the same symptoms or no symptoms at all: I'm i reading too much meaning into this question?
why doesn't the correct answer read:
"People who received the PLACEBO already had the Hepatitis A" instead of people who received the Vaccine. Am i missing something here? Please help! Thanks a lot.

[nbayar1212]

You hypothetical AC is on the right track - the reason D works is that it leaves open the possibility of people in BOTH groups having Hep A before they were vaccinated i.e. the placebo group (as stated in your hypothetical AC and the vaccinated group.

[mjacob0511]

Hmmmm- I still do not get this argument.I ruled out all the ans choice My understanding is that people with the placebo doesn't produce the same symptoms or no symptoms at all: I'm i reading too much meaning into this question?
why doesn't the correct answer read:
"People who received the PLACEBO already had the Hepatitis A" instead of people who received the Vaccine. Am i missing something here? Please help! Thanks a lot.

The paradox doesn't come from the one's who receive the placebo. Being that these individuals never received the vaccine, it has no connection to the the conclusion that the vaccine is completely effective at preventing infection, they could still contract Hep A. The paradox arises from the fact that the people who were given the vaccine still developed Hep symptoms even though we know that the vaccine is 100% effective in preventing Hep.

So the question is how can any of the vaccinated people get symptoms if the vaccine should have prevented it. A simple answer as mentioned above is that they may exhibit symptoms but they don't actually have Hep, so the vaccine could still be completely effective. Choice (D) takes a different approach - the vaccinated people who exhibited the Hep symptoms already had Hep before the test! Notice the first sentence says that symptoms appear no earlier than 60 days after a person gets infected. No less than 60 days is very vague, it could mean one year. Well this clearly resolves the paradox. The vaccinated one's are exhibiting symptoms now during the test, a year after they first contracted the infection, so yes the vaccine is 100% effective in preventing future infection, but these people are exhibiting old symptoms.

[ricardo.e.miranda]

What confused me on this question is that I may have made some assumptions based on what may be some misconceptions about what happens when a vaccine is introduced into our bodies.

In my mind, a vaccine is usually a very small non-lethal dose of a live strain or a dead strain that our immune system reacts to. So, if I am injected with a viral strain, I may or may not exhibit symptoms, depending on my own personal immune system. Either way, I have a malignant microbe in my body, whether alive or dead.

Since the question says that some people from both the placebo group and the vaccine group exhibited symptoms, I thought the paradox would have more to do with people experiencing the placebo effect being in better physical condition than those who received the real strain, since the placebo group would be affected psychologically and not physically. Answer choice C.

I think the part of the stimulus that may be the most important here is where it says that "the vaccine as used in the test is completely effective in preventing infection with the hepatitis virus." This is still somewhat confusing because in my mind people are being infected, by virtue of being vaccinated. When being vaccinated, they are being infected in a controlled manner.

For answer choice D to be correct, then you have to assume that being vaccinated will not cause an already healthy and uninfected person to exhibit symptoms of hepatitis A. Therefore, if they exhibit symptoms of hep A after being vaccinated, they must have already been infected before being vaccinated.

The first sentence of the stimulus seems superfluous or somewhat of a distraction.

[AyakiK696]

Why is E wrong? Is it because of the words "on average," which leaves open the question of why we could say the vaccine is "COMPLETELY effective"?

[JosephV]

Why is E wrong? Is it because of the words "on average," which leaves open the question of why we could say the vaccine is "COMPLETELY effective"?

I believe what you point out as a reason to reject (E) is indeed a valid reason.

In addition, the conclusion of the stimulus is that "the vaccine as used in the test is completely effective in preventing infection." Answer choice (E) says that "those who received the vaccine recovered more quickly." This implies that they had been infected and the vaccine helped them get better.

To answer a possibly objection to my point above: it is possible that all cases of infection happened before the vaccine had been administered. On the other hand, however, it is also possible that at least one infection took place after the vaccine had been given, which goes against the conclusion of "completely effective in preventing infection."