I summarized that from the statistics which were publicly available at that time, simply for the sake of brevity. One data point was more than a 20% mortality rate among some elderly cases - in a small sample. Compare with the data now available for the very young, who have a mortality rate of about zero. Of course, this is all preliminary data, and mortality rates will be firmly established when millions of people have had the disease. (That won't be long from now.) Still, the factor of 100 I used in making the meme probably understates the difference in mortality rates significantly.
