On August 31, 2011, the Court of Appeals for the Federal Circuit (which I'll abbreviate as 'CAFC,' and is also often called simply the Federal Circuit) decided Classen Immunotherapies Inc. v. Biogen Idec, et al., where Classen alleged infringement of three of its patents by several defendants.  The patents in suit covered a method of administering immunizations according to a schedule, in order to minimize the risk of side effects from the immunizations.  The patented methods involved analyzing immunization records from different groups of patients on different schedules, then giving immunizations to a patient according to the schedule of the group with less side effects. 

The immunization records and studies were admitted to be known.  Classen's claimed invention was solely the process of analyzing data discovered by others and applying the results of that analysis.  One of the three asserted patents covered only the steps of analyzing the known data.  This patent was held invalid as an abstract idea.  However, the CAFC held the other two patents covered patentable subject matter because the final step of administering the immunizations according to the more beneficial schedule was "a specific, tangible application" of the abstract idea.

It is clear from the cases that a "specific, tangible application" is necessary for an invention to patentable.  It is less clear, however, where the distinction lies between the conventional or obvious post-solution activity of Flook (often referred to as "insignificant post-solution activity," although the Court did not use that phrase) and the administering of immunizations in Classen.  This issue was not specifically addressed in Classen, so we can hope that future decisions will take it up. 

UPDATE: The Supreme Court's 2012 decision in Mayo Collaborative Services v. Prometheus Laboratories, Inc., on similar facts, sheds more light on these issues.  Please refer to the Prometheus articles on this blog for more information.