The issue of protecting lives now as against risking prolonged economic collapse is already a lively, and potentially vicious, one - especially in the United States. I would not dispute that crashing the economy will cost lives, although the complexity of the current situation (air pollution is reduced for instance) makes it doubtful that we could rely on risk management professor Philip Thomas' estimate that a 6.4% cut in GDP leads to 400,000 lives lost. Without such comparisons being foolproof, the only clear injunction from moral theory comes from Catholic deontology. That tells us to save the lives directly threatened by disease, since it is acceptable to do something (in this case crash the economy) knowing lives will be lost, but when not intending to kill them.
To be clear, I am no Catholic deontologist. Also I agree with cutting perks to older people such as the triple lock on pensions or free TV licences, even though I benefit from some of these myself. Yet, casting an eye across the Atlantic, I would warn the likes of Philip Thomas or Max Hastings about stepping into a minefield. Given the obvious links to national strength and even national self-sufficiency, rhetoric about 'locking down the over-70s' can acquire fascistic overtones. I would not be surprised to find groups Thomas and Hastings would detest getting into the argument.
Much safer for both lives and the economy would be developing global insurance against future pandemics. It is not as though we don't know about natural selection and microbial mutations.