Shouldn my photographer have a back up in case he/she is sick on my wedding day?
That would be ideal, but consider the plight of the backup photographer who has to turn down weddings just in case she/he is needed for yours. Professionals are part of a network of photographers, and do have many people they can call in an emergency. No doubt as your wedding approaches you will have many far more significant worries. Let your photographer manage this problem. I recommend that you always select a photographer that belongs to a PPA affiliate; this ensures a high level of professionalism.