You can imagine the drug would help, sure. But that's it – your imagination. But yeah, if we assumed the Modafinil was indeed a proven "cure" against sleeping while driving, and it was given free, then the situation would have a similar structure as the one analyzed by the author. Obviously, they still differ significantly: a) you would have probably to take Modafinil before each drive – vaccines have a more permanent effect b) it is easier to track vaccinations than taking a drug, it's much more manageable.

This is not only a risk management game – your simplified "absurd" examples are of the kind: "author wants to bar risky situations, why not bar big cars, they're risky". One has also to weight various social factors/costs. If barring bigger cars from the road would be beneficial for society, then yeah, let's do it, but I wouldn't bet on that. The vaccinations have some added costs (production, distribution) and risks (side-effects), but the question is whether the cost/risk of the longer pandemic isn't even bigger (AFAIR it is). I don't say, that OP is right that people should be forced to be vaccinated, but I don't find it absurd given that we've already sacrificed many other freedoms for the society. It's like @mayewsky writes, we already bar some drivers (because of age/health state/previous offenses against the law) from driving. It's nothing new and it's not controversial AFAIK.