Between the years of antigenic shifts, antigenic drifts
have happened almost annually and have resulted in outbreaks of variable extent and severity.
Because of antigenic drift
, the formulation of vaccine changes each year.
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
"We have to ask the question, why are these animal influenza viruses showing so much antigenic drift
? I would argue that contributing to this is the use of bad vaccines."
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.
) we need to make a new influenza vaccine each year.
in H5N1 avian influenza virus in poultry is driven by mutations in major antigenic sites of the hemagglutinin molecule analogous to those for human influenza virus.
This process evaluates whether genetic changes in circulating viruses have led to antigenic drift
away from the vaccine reference virus.
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.
Despite significant efforts being put into the development of avian vaccines, serological surveillance represents one of the major tools for evaluating the immune state of avian populations especially for the ability of certain subtypes to mutate (antigenic drift
mechanism) due to their long-term circulation among vaccinated populations .
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.