Here's a tale that takes a concept from one of H.G. Wells' novels...
...a concept which was based on real-life events from Earth's history!
Yep, it's the classic ending from War of the Worlds!
Note: The movie version of Wells' First Men in the Moon also incorporates the "germs kill aliens who haven't been exposed to them" concept, but it's not in the original novel!
As to real-life, European settlers inadvertently brought a plague to North America and caused an epidemic that decimated a number of native tribes that had contact with them.
While the writer of this tale from Charlton's Outer Space #1 (1968) is unknown to me, the art is by Charles Nicholas and Vince Alascia.