In March of 2009, Wyeth sued then Schering-Plough's Intervet in Delaware federal court, for patent infringement -- the patents in issue relate to several of Wyeth's pig virus vaccine products. It was then alleged that Intervet infringed those patents when making and selling its Circumvet® PCV and Porcilis® vaccines, for PCVAD. Just a couple of days ago, New Wyeth (now owned by Pfizer), was issued a new patent, on more of its pig virus vaccine technology -- technology useful in making the PCVAD vaccine.
So -- New Wyeth sued New Merck again, yesterday, also in Delaware federal court, for infringing this newly-issued patent. The complaints -- March 2009 and May 2010 (as a pair of PDF files).
Responsibility for any damages here will presumably transfer over to the New Merial Joint Venture, when and if these vaccine products are transferred to the Merck-Sanofi-Aventis joint venture, in 2011. That's about when both of these pieces of litigation are likely to draw near to a trial date. I'll keep an eye on 'em, just the same.