Logical Reasoning

PT120 · S1 · Q19 There have been no new

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There have been no new cases of naturally occurring polio in North America in recent years.

Conclusion

We should switch from OPV to IPV as the most commonly used polio vaccine for NA children.

Evidence

OPV causes about 12 new cases of polio each year in NA. If we substituted IPV for most immunizations, then it would cut the number of cases about in half.

Evaluate

Given That ... using IPV would probably result in half as many vaccination-caused polio cases as OPV, How Can We Still Argue That ... we should not make IPV the more common vaccine?

When arguments are comparative in nature, we're usually being shown an Incomplete Comparison, and we need to judge what other similarities or differences two things may have.

Sure, IPV has an advantage when it comes to how many cause of vaccine-caused polio it's likely to lead to. But what are IPV's disadvantages?

- does it lead to more naturally occurring cases of polio (I'm assuming that inactivated polio vaccines might not trigger the desired immune response as reliably as live polio vaccines)?

- does it cost way more?

- is it way harder to administer to kids?

Obviously 12 cases of pediatric polio is a big concern, but it's not a huge number. If the IPV has significant downsides, it might be something we choose to live with.

Goal

Find an answer that says something comparative negative about IPV.

19.

Which one of the following, if true, most weakens the argument?

  1. Correct

    If IPV replaces OPV as

    Why this is right

    Here's a negative difference. IPV would lead to some new cases of naturally occurring polio. This is very weakly worded (at a least a few new cases), but it doesn't take much to negate the supposed advantage of IPV. IPV was supposed to take us from ~12 cases to ~6 cases of polio caused by vaccine. So we prevented 6 cases of polio. But if IPV also causes at least 3 new cases of polio, we're definitely weakening the argument. It's mathematically possible that we still come out 1 or 2 cases ahead by using IPV, but that's already weakened the force of the Evidence (we are preventing 1-3 cases of polio by switching, not 6). It's also possible that naturally occurring polio cases are worse than vaccine-caused polio cases, so maybe we shouldn't even treat the numbers so equivalently. It's possible that IPV causes more than 10 or 20 new cases (at least a few new cases). So this answer creates a possible way in which the Conclusion could be wrong, and it definitely dilutes the force of the Evidence.

    Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

    61% picked this

  2. The vast majority of cases

    No Impact

    The backstory of these cases of OPV-caused polio isn't really relevant, unless we somehow know how that would be better/worse/same in a world in which we used IPV instead. If we were reading this as, "We don't need to get rid of OPV. The 12 cases are from specific, preventable things", we'd really be adding the preventable part of that. If it were already possible to identify and preempt these specific kids from getting vaccine-caused polio, wouldn't we already be doing it?

    28% picked this

  3. A child’s risk of contracting

    No Impact

    This is just turning 12 new cases into a percentage / ratio. We already knew that this was a very tiny number of cases, relative to "all the children being immunized in North America each year".

    3% picked this

  4. Although IPV is preferred in

    Unclear Impact

    This probably feels like the 2nd best answer. Since we were looking for a way to argue that we should still use OPV, the fact that most countries with good immunization programs use OPV sounds like it supports our argument. But LSAT isn't took keen on supporting a plan just because other people are doing it. The fact most people believe something or do something doesn't make it "true / correct". This answer doesn't engage with the evidence the way (A) does, so it should seem less appealing as a type of LSAT objection.

    1% picked this

  5. IPV, like most vaccines, carries

    Unclear Impact

    This potentially gives us a negative difference about IPV, but is it a difference? It says that IPV, like most vaccines, carries a slight risk. So this might be something that applies equally to OPV.

    7% picked this

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