Flu science points to another culprit when vaccines fail — us

The idea is that the first flu viruses your immune system encounters make indelible marks on it. A person born in 1970 whose first influenza A infection was caused by an H3N2 virus will always mount a better immune response to H3N2 viruses — or that component of the vaccine — than she will to an H1N1 virus or vaccine. But a person born in 1949, when H1N1 was the only influenza A virus circulating, will likely always have an underwhelming response to the H3N2 component of the flu shot. The phenomenon is called “original antigenic sin” in the influenza literature. It’s also known as “imprinting.”

Source: Flu science points to another culprit when vaccines fail — us