Antigenic shifts are associated with the epidemics and pandemics of influenza A, whereas antigenic drifts
are responsible for more localized outbreaks of varying extent.
Because influenza viruses are constantly undergoing antigenic drift
, the composition of vaccines must be updated each year, and annual vaccination is recommended.
This type is prone to antigenic drift
, resulting in new strains.
refers to successive small point mutations that occur with successive replication.
At present that is not the case, but influenza viruses are notorious for their ability to mutate via a process called antigenic drift
Experience in the production of influenza vaccines is also considerable, particularly because vaccine composition changes each year to match the antigenic drift
in circulating virus.
Influenza vaccination provided protection against vaccine-like influenza A (H3N2) viruses that had not undergone significant antigenic drift
and against influenza B viruses, which predominated later in the season (1, 3, 6).
The vaccine will protect against circulating strains that have not undergone significant antigenic drift
, including the influenza B viruses, which have comprised about 9% of those collected to date.
of the pandemic 2009 A(H1N1) influenza virus in A ferret model.
Current vaccines may be safe and immunogenic, but they are highly vulnerable to antigenic drift
and shift, which compromise efficacy and require reformulation and repeated immunization.