Immunity against MERS-CoV has been noticed many times in different parts of the world in camels. The transmission of this disease from camel to human is very controversial. The workers in camel farms (having all camels MERS-CoV positive) did not show any sign of this fatal disease.
https://camel4milk.wordpress.com/2016/08/12/blaming-dromedary-camel-for-mers/