<prompt> False about antigen drift-Causes pandemicOccurs due to mutationOccurs more frequentlyAffected by previous antibodies  <response>: Antigenic shift not drift is responsible for pandemic.Antigenic drift occurs due to point mutation.Antigenic drift occurs more frequently 2-3 years than antigenic shift 10-15 years.Antigenic drift is influenced by the presence of antibodies to the predecessor strains in the host population. 