PrepTest 129, Section 3, Question 11
Many vaccines create immunity to viral diseases by(95 more words not shown)
Which one of the following,(8 more words not shown)
- AMost of the(18 more words not shown)
- BSome laboratory animals(16 more words not shown)
- CResearchers developed a(17 more words not shown)
- DThe virus that(27 more words not shown)
- EMany children who(16 more words not shown)
Reading the argument
We don't need the whole virus to stimulate the relevant antibodies. According to the passage, a suitable part of its outer coating does that job as effectively. The practical challenge is finding the right part.
Imagine a virus with three parts, only one of which triggers the antibody production we need. Isolating just any part wouldn't be enough; doctors need that effective part. They have now isolated a suitable portion of the hepatitis E virus, so I can see why they expect to develop a vaccine.
But permanent immunity?
Producing antibodies now and remaining protected forever are different claims. What if protection fades over time and another dose is needed? We could also ask whether everyone will respond successfully, but the word “permanent” gives us the clearest unsupported step.
What we’re looking for
The question asks for evidence against the doctors' claim. I'd look for a reason to doubt that the protection lasts indefinitely. We can accept the discovery and the antibody response while questioning the duration of the resulting immunity.
Working the answers
- ACorrect
At first this might look like a fact about who gets hepatitis E rather than a fact about a vaccine. The earlier exposure is what makes it relevant. These young adults probably encountered the virus as children, yet they later contracted the disease.
Connect that with the passage's comparison: exposure to the suitable portion is as effective as exposure to the whole virus in stimulating the relevant antibodies. If earlier exposure to the virus has not provided lasting protection into adulthood, there is reason to doubt that introducing the isolated portion will produce permanent immunity. A need not mention vaccination explicitly to challenge the doctors' expectation about how long protection will last. It gives counterevidence, not proof that no vaccine could ever work.
- B
Immunity to several strains concerns the range of protection, not its duration. Those laboratory animals could develop broad protection that later fades. The answer does not give a reason to doubt permanent immunity to hepatitis E, and the development of immunity itself points toward success rather than failure.
- C
Success with hepatitis B does not undermine the proposed hepatitis E vaccine. If anything, a successful vaccine developed after isolating another hepatitis virus makes the general project seem plausible. It still tells us nothing about a loss of protection over time in the present case.
- D
Widespread exposure makes protection potentially useful, but it does not tell us whether that protection lasts. Many people encountering hepatitis E is consistent with either lasting or temporary immunity from a vaccine.
- E
Children exposed to other viruses sometimes do not develop those diseases. That does not establish that protection against hepatitis E fades or that the proposed vaccine will fail. Unlike A, it gives no earlier-exposure/later-illness pattern bearing on the permanence claim.
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