All are true about Antigen drift except -
Antigenic drift the gradual sequential change in antigenic structure occuring regularly at frequent intervals. Antigenic drift is due to mutation and selection .It accounts for the periodic epidemics of influenza. REF:ANANTHANARAYAN AND PANIKER'S TEXTBOOK OF MICROBIOLOGY 9TH EDITION PAGE NO-499
It causes pandemic
Occurs due to mutation
Occurs frequently
Minor antigenic changes
Virology