PrepTest 47, Section 2, Question 19
There have been no new cases of naturally occurring polio in North America in recent years. Yet there are approximately 12 new cases of polio each year in North America, all caused by the commonly administered live oral polio vaccine (OPV). Substituting inactivated polio vaccine (IPV) for most childhood polio immunizations would cut the number of cases of vaccination-caused polio about in half. Clearly it is time to switch from OPV to IPV as the most commonly used polio vaccine for North American children.
There have been no new cases of naturally occurring polio in North America in recent years. Yet there are approximately 12 new cases of polio each year in North America, all caused by the commonly administered live oral polio vaccine (OPV). Substituting inactivated polio vaccine (IPV) for most childhood polio immunizations would cut the number of cases of vaccination-caused polio about in half. Clearly it is time to switch from OPV to IPV as the most commonly used polio vaccine for North American children.
There have been no new cases of naturally occurring polio in North America in recent years. Yet there are approximately 12 new cases of polio each year in North America, all caused by the commonly administered live oral polio vaccine (OPV). Substituting inactivated polio vaccine (IPV) for most childhood polio immunizations would cut the number of cases of vaccination-caused polio about in half. Clearly it is time to switch from OPV to IPV as the most commonly used polio vaccine for North American children.
There have been no new cases of naturally occurring polio in North America in recent years. Yet there are approximately 12 new cases of polio each year in North America, all caused by the commonly administered live oral polio vaccine (OPV). Substituting inactivated polio vaccine (IPV) for most childhood polio immunizations would cut the number of cases of vaccination-caused polio about in half. Clearly it is time to switch from OPV to IPV as the most commonly used polio vaccine for North American children.
Which one of the following, if true, most weakens the argument?
If IPV replaces OPV as the most commonly used polio vaccine, at least a few new cases of naturally occurring polio in North America will result each year.
The vast majority of cases of polio caused by OPV have occurred in children with preexisting but unsuspected immunodeficiency disorders.
A child's risk of contracting polio from OPV has been estimated at 1 in 8.7 million, which is significantly less than the risk of being struck by lightning.
Although IPV is preferred in some European nations, most countries with comprehensive child immunization programs use OPV.
IPV, like most vaccines, carries a slight risk of inducing seizures in children with neurological diseases such as epilepsy.
Explanations
What a ridiculous argument.
This author wants us to change from a vaccine leading to 0 natural Polio cases and 12 vaccine-caused ones, to a vaccine that could very easily lead to natural Polio cases in order to reduce the vaccine-caused cases from a handful to less-than-half of a handful. Nonsense.
Turns out to be a Weaken question, so I know my job: I need an answer choice that pokes at the vulnerability I've pointed out. Something like, "Switching to IPV would lead to at least some number of naturally occurring Polio cases."
Let's see.
Yes! Right off the bat, and a dead ringer for our prediction. This is a devastating weakener. If IPV leads to new cases of naturally occurring polio, then why would we trade these new natural cases for the handful of vaccine-caused ones we have now? This is the answer.
Nah, this doesn't weaken. All this does is describe who is susceptible to the problems with OPV and how they are affected. This doesn't help me attack the recommendation to switch vaccines.
Nope. Cool story, bro. But this doesn't help me at all. It simply qualifies the likelihood of being struck by lightning. Which, based on the fact we know 12 people get vaccine-caused polio per year from OPV, I would estimate is around 12 people getting struck by lightning per year.
Nah. Knowing that most countries use OPV over IPV doesn't tell me why I should stick with OPV. It just tells me that we'd be doing what most other countries would be doing.
Nah, trickier, though. If this is true of most vaccines including IPV, then it's probably also true of OPV, which doesn't give us a strong case one way or the other about which vaccine to use.
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