IMO:If India has natural herd immunity and the delta variant ran through there like the way it did then that does not speak well for natural antibodies.
I don't think people take into account that how a body reacts to the virus, is a matter of your genetics. So basically, it's the luck of the draw.
Survivors didn't survive because they had natural antibodies;
Survivors get natural antibodies because their genetics were such that, they were able to defeat the virus ... and the RESULTS were natural antibodies.
The luck of the draw. A lot of people are gambling, and don't even know it.