False about antigen drift-
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.
Causes pandemic
Occurs due to mutation
Occurs more frequently
Affected by previous antibodies