In terms of severity, Covid is not in the same league as Spanish Flu, primarily due to the W-shaped mortality curve and higher observed mortality rates mentioned above. Besides these facts, its hard to make estimates how the numbers for both pandemics would be different if Covid was in 1918 and Spanish Flu occurred now. In general, populations are older now with more of the comorbidities that make them more vulnerable to Covid, but medical care has much advanced since 1918.