Retracted research can be especially problematic when cited in systematic reviews or meta-analysis. To quote Elizabeth Wagner, former chair of COPE (Committee on Publication Ethics): "For articles presenting original research it’s unlikely that any other cited work would alter the conclusions, since these will usually relate only to the new work, and that won’t be affected. However, it might slightly change the emphasis of the Discussion section since a retraction will remove a citation that presumably [either] supports or opposes the author’s own work.
However, for review articles, and particularly systematic reviews that combine study findings using meta-analysis, the removal of one study might well affect the conclusions, so authors of such articles should react promptly and, ideally, re-do their meta-analysis." --Retraction Watch blog entry by Alison McCook, 11/1/2016