Remember when vampires took over the world in 2010?
No, I don't mean the Twilight or True Blood franchises...
The early 1970s was one of the more pessimistic periods in pop culture.
Between pollution/ecology concerns, potential overpopulation, and possible war, fear was running wild in pop culture, in particular, movies.
The near-future was believed to be a potential Hell on Earth, with movies like A Clockwork Orange (crime and violence held in check only by mind-control), Soylent Green (overpopulation and food shortages relieved by using humans as food), ZPG (controlled breeding to avoid overpopulation), and Omega Man (man-made plague kills most of humanity and leaves remainder as mutant ghouls).
Even films about the distant future like Zardoz and the Planet of the Apes series showed humanity as either decadent and collapsing, or under control of other species!
Writer Larry Hama and penciler Pat Broderick combined several of the concepts in Seaboard's Planet of Vampires #1 (1973).
It was one of the stronger titles of the new company formed to compete with Marvel and DC, but both internal problems between the publishers and creatives as well as failure to gain newsstand space (there were no comic shops at the time), doomed the company to a short life.