That's not how ADE works... If any strain of covid had a functional ADE replication path, we would have seen explosions of cases and deaths from that strain even before we started vaccinating. ADE functions off antibodies, not off vaccines. Plenty of people had antibodies from previous infections of covid, prior to any vaccine rollouts. The reason delta is behaving differently is because it replicates so fast. The viral load is such that it brute forces your immune system. Natural immunity or vaccine generated are irrelevant if you're body can't make antibodies fast enough. Immunity helps, for sure. But it's just not enough in this case. We need other therapeutics and preventative care on top of immunity.