I just read an important article on Porcine Respiratory Disease Complex over Chanhee Chae's work. He is from South Korea and had two great points:
(1) If you have both Porcine Reproductive and Respiratory Syndrome and Porcine Corona Virus-2, you will need to vaccinate for Porcine Corona Virus-2!(1)
(2) If you have Mycoplasma Hyopneumoniae and Porcine Corona Virus-2, then you will want to vaccinate for Mycoplasma Hyopneumoniae. (1)
(1) "What to do with Porcine Respiratory Disease? Change Chae Seoul National University, South Korea