We keep reading about younger, healthier people including children getting very sick or dying from delta, and the disease progression seems to be quicker. As far as I know, the data hasn't yet been assembled to assess whether that means delta is more dangerous or simply that a wide range of the population is getting infected due to its being far more contagious.
The disproportionate number of younger people unvaccinated definitely is contributing to the delta wave skewing much younger (in addition to increased contagion and possible (probable?) increased virulence)