Bivirkningerne, der har været rapporteret i undersøgelserne med en hyppighed > 5%, var oral candidiasis (14%), pådraget lipodystrofi (13%), nedsat CD4- lymfocytter (8%), nedsat appetit (8%), øget gamma - glutamyltransferase (9%), rygsmerte (5%), øget amylase i blodet (6%), øget mælkesyre i blodet (5%), cytolytisk hepatitis (6%), øget lipase (6%) og smerte i lemmerne (6%).
HCV/HIV co-infected patients For HCV/HIV co-infected patients receiving ViraferonPeg in combination with ribavirin, other undesirable effects (that were not reported in mono-infected patients) which have been reported in the larger studies with a frequency > 5% were: oral candidiasis (14%), lipodystrophy acquired (13%), CD4 lymphocytes decreased (8%), appetite decreased (8%), gamma-glutamyltransferase increased (9%), back pain (5%), blood amylase increased (6%), blood lactic acid increased (5%), cytolytic hepatitis (6%), lipase increased (6%) and pain in limb (6%).