All of the following statements are true regarding poliovirus except:

There are three serotypes of poliovirus. They are type 1, 2 and 3. Serotype 1 is the most common type, it is the most common serotype causing polio epidemic. Mutated Type 3 is the most common cause of vaccine induced paralysis. Poliovirus belong to enterovirus group. It is a single stranded RNA virus. It has a naked protein capsid and a dense central core of RNA. It is spread through feco-oral route. Infection with poliovirus gives lifelong immunity to the homologous virus type, but does not confer immunity to other two viral types. Ref: Oski's Essential Pediatrics By Michael Crocetti, 2nd Edition, Page 322