To date, retreatment with IFN after the occurrence of IP has been reported in only three patients with hepatitis C. Of these, two cases changed from IFN-α2b or pegIFN-α2b to pegIFN-α2a and experienced relapse of IP [22, 23], whereas the other case changed from pegIFN-α2a to pegIFN-α2b and completed the therapy without relapse [24]. Here, IFNA1 is linked to hepatitis A virus infection.