XKCD #2406

Viral Vector Immunity

We've secretly replaced this customer's instant coffee with our patented substitute. Let's see what she ... uh oh, I think she spotted us through the window. Now she's getting something from the closet ... oh jeez, she has a sword! Run!!

All artwork belongs to xkcd.com and the respective copyright holders. XKCD WebComic Iterator is an absolutely free service that allows users to browse all xkcd comics and also provides a subscription service that delivers one comic everyday to their mailbox.
XKCD WebComic Iterator is not affiliated in way with the xkcd.com website or its creator(s).

Users will never see ads or any other form of monetization on the newsletter or the website.

Warning from xkcd.com : This comic occasionally contains strong language (which may be unsuitable for children), unusual humor (which may be unsuitable for adults), and advanced mathematics (which may be unsuitable for liberal-arts majors).