In answer why arguments like jumping or falling off something fatally high don't really exist in any serious form, is for the simple reason typically there's an easily recognised clear starting and end point, where chances of fatality can faithfully derived from extrapolation and correlation of injury due to falling from various heights, as well as statistics of previous incidents from similar heights. On the other hand more fluid situations generally, such as if a vaccine or some substance works to a suitable effectiveness, in reality have no clear firm starting point, more often a blurred end point and wide range of exceptions in between. However there are those who think the starting point is fixed ... or close to fixed with or without caveats -- exempting really old people in poor health for example.
Trying to explain to the naysayers were hard if not near impossible when it came to vaccinating for covid in my locale. Eventually I ended up on simple little fictional story of whether to stay put in a small boat, or evacuate from the coast inland from a large few hundred foot tidal wave, to demonstrate that someone's starting point wasn't all that clear and could not be taken for granted
Oh yes on the people who whine they still got a bit of the flu, the jab didn't work ... that's the other thing about vaccines that few people (even well educated) have understood well, is that a vaccine is not a force field that pushes or repels, it's actually more an opportunity for the body to get some practice, develop the proper weaponry to counter with when the problem arrives ... but not everyone's body is that good at creating a sufficient defence, and a lot of factors come into play. Some people need more practice to get it right.
The last paragraph on denial ... and deep down. When it comes to gambling with life, yes, I think to some extent we've witnessed it with the ivermectin cure BS. I know for instance that when it was used to treat heart worms in dogs, a small percentage did not react that well to the normal dosage. Humans tolerate iirc a little bit better and have a similar percentage of reaction to a normal dosage but no where near as severe. At 6 times the rate, the product crosses the blood brain barrier to a point that in those dogs that were accidentally dosed incorrectly, most survived but it was touch and go, they were for a time afterwards unable to walk and then had staggers until eventual recovery. We do not hear any real reports of any person getting even a few multiple of the regular dosage ... except for the wordsmithed papers giving that impression of really high dosage rates, but digging deeper, they were in fact actually not receiving an at once dose but a number of small doses over a few days minding ivermectin's half life. I had calculated regular cattle /horse rated ivermectin would need 100x dosage to achieve the level that was said to stop covid ... a Canadian hospital examined how much imvermectin was active from the oral product they used to treat humans and the amount of dose required to achieve the mythical level to stop covid was approx just 55 times the regular dose. We, the world, never heard any certified instances where it was used at 50x regular dosage rates ... in fact, when the BSers were nailed down, they instead claimed the regular low dose must have worked so there ... if only I could get away with only paying a dollar for every 50 or 100 I owed.