Since that was a parable about communist infiltration and subversion... still works! 
Jason Pratt is correct.
The Puppet Masters by Heinlein and one of his other books were also discussed as parables of communist infiltration.
From Wikipedia:
Some reviewers saw in the story a commentary on the dangers facing America for turning a blind eye to McCarthyism. Leonard Maltin wrote of a McCarthy-era subtext,[21] or of bland conformity in postwar Eisenhower-era America. Others viewed it as an allegory for the loss of personal autonomy in the Soviet Union or communist systems in general.[22]
For the BBC, David Wood summarized the circulating popular interpretations of the film as follows: "The sense of post-war, anti-communist paranoia is acute, as is the temptation to view the film as a metaphor for the tyranny of the McCarthy era."[23] Danny Peary in Cult Movies pointed out that the addition of the framing story had changed the film's stance from anti-McCarthyite to anti-communist.[19] Michael Dodd of The Missing Slate has called the movie "one of the most multifaceted horror films ever made", arguing that by "simultaneously exploiting the contemporary fear of infiltration by undesirable elements as well as a burgeoning concern over homeland totalitarianism in the wake of Senator Joseph McCarthy's notorious communist witch hunt, it may be the clearest window into the American psyche that horror cinema has ever provided".[24]
