Note the exact same drop in cases for the same time of year as this year, and that without the vax.

Here’s the link in case the graph doesn’t show up.
https://www.cdc.gov/mmwr/volumes/69/wr/figures/mm695152a8-F.gif
A no-go on both the pic and URL.
But I’ve seen recent data on a virtual swap between the flu and SARS cases.