Herd Immunity sounds promising for a once-in-a-lifetime disease. But if immunity only lasts 12 to 24 months, that’s a several times per decade disease, which sounds like a less attractive deal.
Let’s say the Infection Fatality Rate is just 0.5% per run to Herd Immunity, which would be achieved at, say, 60% of the US population of 330 million or about 1,000,000 deaths each time.
Let’s say it takes one year of widespread illness and dying to reach herd immunity and then the whole process starts over again 18 months later. That’s four times per decade. But it could be even more frequent than that.
That raises the question of how bad the next several runs to herd immunity would be. My guess is the IFR would decline because you are progressively killing off the the most vulnerable so the disease faces diminishing returns the next several times through. Perhaps people even get more resistant to the disease each time they have it.
Plus, obviously huge resources will be devoted to improving therapy each time. If a million plus people die in America the first run to herd immunity, we will attain a huge sample size of data of how to treat people, which should prove useful in lowering the death toll in subsequent waves.
But then again maybe not. Maybe people get progressively more worn down each time they catch it?
Now it could be that the timing of a vaccine works out perfectly and we get to Herd Immunity the first time about a year before a vaccine arrives so we don’t have to do it all over again and again.
But then again, how do we know herd immunity will happen all that fast? You want it to arrive slowly enough that the hospitals aren’t overwhelmed, but not so slowly that the economy never gets to revive from most people being (briefly) immune. But what if lots of people want to hunker down and avoid being a sacrificial lamb? This sounds like a Herd Immunity strategy might blunder into a worst of both worlds, with huge numbers being made deeply ill but the economic downturn dragging on for several years as scores of millions hunker down and don’t spend a lot of money pursuing an active social life.
Advocates of a Herd Immunity strategy really need to get out their spreadsheets and do the math of how this would turn out to be a good thing. Perhaps it is the best alternative, but, please, show your work.