This news was greeted with controversy and has had to be subsequently justified in terms of developing defences against such an antigenic shift
occurring in the wild.
can occur when RNA from one influenza virus combines with the RNA of another influenza virus and results in a new subtype.
But occasionally, influenza A viruses undergo formation of an entirely new subtype through a process called antigenic shift
, resulting in a new H or N protein, which creates the possibility of a pandemic.
aside, having your child vaccinated against the flu is not a 100% guarantee that she won't get the flu, but it greatly increases her chance that she won't suffer from severe symptoms.
is a major and abrupt genetic reassortment, made possible when two subtypes exchange genetic material.
A major change of this type in the Influenza A viruses is known as antigenic shift
. Antigenic shift
results when a new Influenza A subtype to which most people have little or no immune protection infects humans.
It is possible that cross-species transmission could lead to an antigenic shift
, whereby avian and human strains of influenza virus that are circulating at the same time swap genetic material, resulting in a novel, more virulent subtype.
More rarely, about every 25 years on average, a more serious antigenic shift
occurs involving an exchange of gene segments between human and avian influenza viruses.
Although long-term storage might have resulted in antigenic shift
of the vaccine, DNA viruses such as vaccinia are not prone to antigenic variability (5).
The problem is that the predominant H3N2 variant has been "uncharacteristically" stable over the last few years, and a significant antigenic shift
is anticipated, Dr.
"`Antigenic drift' causes subtle changes in virus antigens [the flags which alert our immune defences to invasion], making it harder to recognise, but it is antigenic shift
- human `flu's ability to combine its DNA with other influenza strains from birds, pigs or horses - that causes real havoc.