You make some compelling arguments and I'll look into Scarlett fever but if immunisations are in fact crippling immune systems why did the amazing decrease in disease happen at all?
That is actually part of that link I posted. There was less whooping cough before immunisations were so widely used, and whooping cough incidences have been increasing over the past 20 years.

1980
Reported Cases - 124
Antigen Coverage - 33%

2009
Reported Cases - 29,545
Antigen Coverage - 92%

ETA: Just got DH the mathematician out of the dust to quell any population increase theories.

Percentage of the population:
1980: 0.00085%
2009: 0.139%