> If they weren't shielded from liability, would there be any company willing to take on the risk of administering the vaccines to 92%+ of the population

Absolutely yes. Every other industry is exposed to the risk created by their products - including makers of cars, heavy machinery, drugs, food, beverages, and airplanes - and continues to sell their products. There's no airliner deficit because the major companies are scared of the potential liability resulting from a crash, or beer deficit because major breweries are averse to the risk of a bad batch poisoning hundreds of people.

The claim that vaccine companies are somehow different than car companies, or drug-makers (who you can argue have also "created a massive net-good for society" - which is also a bad argument), or every other industry, is extraordinary, and requires extraordinary evidence.

> we as a society have determined

Objectively false. There has been no general vote on this issue, there have been no politicians that ran on platforms around this issue, and most of the individuals that I know do not support this decision - in fact, as far as I know, the only inputs into the legislation were from pharmaceutical companies, which is the opposite of "society". This claim is absolutely absurd, and equivalent to arguing that "we as a society have decided that personal data mining for the purposes of advertising is OK" just because that's the way the legal system is currently set up.

> the companies that develop these vaccines shouldn't be punished for creating a massively net-good for society

This is a snuck premise. This is no "punishment" at all for developing vaccines, and no one is forcing these companies to create or sell them; this is forcing them to ensure that their products are as safe as humanly possible by providing financial incentives to do so, which not only happens with every other industry, but is the only sane thing to do - if you sell something that people put into their bodies, there is no argument that you can make that you shouldn't also be liable for any negative consequences that happen as a result.

You can make an argument that cars, or antibiotics, or phones, or cheap+healthy+readily-available food have all been beneficial for "society" - and yet, the makers of all those things are equally liable for bodily harm arising from (proper) use of their products.

Moreover, forcing manufacturers to be liable for their products has been a net good for society, as its forced them to invest significant resources in ensuring that the things that they build are safe. Consider the high standards for food safety that we have now, and the incredible amounts of testing and safety engineering that go into building automobiles and airplanes - if manufacturers weren't liable, none of that would have happened. More concretely, if vaccine manufacturers were forced to take responsibility for their products, and there were actually high numbers of long-term side effects - the manufacturers would do research into understanding their interactions with the body better, and they would get safer.

But, of course, vaccine side-effect incident rate is extremely rare, because they're completely safe, so manufacturers would rarely have to pay out in the first place, right?

I suppose that I asked "why do people think that it's a good idea" not "is this reasonable/just/excusable", and so your comment was an answer to that - but it definitely doesn't seem like this is something you can actually justify.

Also, I'm curious: if the manufacturers aren't liable for injury or death from their products, then who do you think is?