Callie the calf is just your average, run-of-the-mill dairy cow, who spends her days playing in the pastures and having fun with her friends and family. Then, one day, Callie learns of a mysterious illness spreading through her herd. Everyone seems to have a lot of opinions on how to stop the virus, but how is Callie to know the truth? And even if she can, what can just one calf really do to keep her herd safe? Follow along with Callie in "Callie's Quest for Herd Immunity" as she learns all about contagious illnesses, vaccines, and what she (and you!) can do to keep the herd healthy.