Here's what rhymes with immunserum.
                        
                        
                    
                                harem  antiserum  Words that almost rhyme with immunserum
heron  vellum  velum  felon  melon  cerebellum  antebellum  flagellum  watermelon  venom  phenom  seldom  septum  denim  spectrum  welcome  rectum  unwelcome  addendum  plenum  bedlam  jetsam  webcam  momentum  plectrum  bubblegum  referendum  interregnum