I didn't want to leave a blank during the timed PT so I chose B even though I really didn't like any of the options at all even after BR.
For A, which is the credited AC, we are told OPV causes 12 cases + no natural cases of Polio each year while IPV causes only 6 + a "few" natural cases.
In this context, it appears to me that a "few" could refer to any single digit number given the values provided of the cases created by the vaccines in the stimulus. So if we take A to be true, then IPV total cases to be 6 + (2) through 6 + (5), could reasonably be a strengthener in my view. So could this choice not be a strengthen, neutral ((6) + (6)), or weaken, thus invalidating it?
Are we simply meant to infer that a "few" is defined in relation to the total population of North America, presumably some large number in the hundreds, if not thousands, and NOT in relation to the value of the "artificial" cases, 12 and 6 by the OPV and IPV respectively?
Admin Note: https://classic.7sage.com/lsat_explanations/lsat-47-section-1-question-19/