I be taking any Eff'n vaccine. Here's just one of the unknowns that we don't know about this virus here's why I won't take a vaccine. HIV "false" positives.
https://www.nytimes.com/2020/12/11/world/australia/uq-coronavirus-vaccine-false-positive.html

Are they enforcing it though? Chicago has a testing/quarantine requirement for people visiting, but they are not enforcing it because they lack the manpower to do so

is this new? I flew into DC a couple weeks ago and I didn’t have any issues!

From the Southwest Airlines website

Anyone traveling to Washington, D.C., will be required to self-quarantine for 14 days.
All Passengers who show proof of a valid negative COVID-19 PCR test taken within 72 hours prior to arrival will not be subject to the quarantine rule. If your visit is longer than 3 days, you will need a secondary test with another negative result within 3-5 days to be exempt from the quarantine rule. For more information, visit here.
Travel to and from Maryland and Virginia are exempt.
For more information, visit the District of Columbia’s official website.

Or fly into another state would be better. You can drive in from many states very easy!!!