The virus uses our immune system against us. Think Aikido using your opponent's strength, or a gravity assist for interplanetary flight. A modern virus attack is higher order, which is what makes designing vaccines so hard. Screw up, and you're just helping the virus. Early variants of COVID-19 were hardest on the old in part from weakness, but in part because of a well-developed immune system to target.

Anyone who's been to India can see that even the young have robust immune systems. Virus variants have finally dialed this in.

Anyone who's been listening in on research seminars since the pandemic start has heard many versions of this. Here is a recent lay account: https://www.newyorker.com/magazine/2020/11/09/how-the-corona...