Every several months or so the topic of Google and social signals comes up and each time it gets into a Googlers hands, they say no - it is not used directly for ranking.
Gary Illyes said it again on Twitter. The question was "Some controversy over whether Google takes social into account for SEO — perhaps Louis Gray will settle this in our next session! #social16" Gary responded, "the short version is, no, we don't."
Here is a video he referenced from Matt Cutts back in 2014 and it has not changed:
Let the controversy and endless debate continue.
Forum discussion at Twitter.