There have been no new

Answer choices

1. A

   Correct60% picked this

   If IPV replaces OPV as the most commonly used polio vaccine, at least a few new cases of naturally occurring polio in

   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.

   60%
2. B

   No Impact28% picked this

   The vast majority of cases of polio caused by OPV have occurred in children with preexisting

   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%
3. C

   No Impact3% picked this

   A child’s risk of contracting polio from OPV has been estimated at 1 in 8.7 million, which is significantly less than the

   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%
4. D

   Unclear Impact2% picked this

   Although IPV is preferred in some European nations, most countries with comprehensive child immunization programs

   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.

   2%
5. E

   Unclear Impact7% picked this

   IPV, like most vaccines, carries a slight risk of inducing seizures in children with neurological

   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%