Key points from article :
Research finds there are only two types of hemagglutinin protein on surface of influenza A virus.
Chances of falling ill from a new strain of flu are at least partly determined by the first strain they ever encountered.
75% protection rate against severe disease if patient exposed to a virus with the same protein motif when they were a child.
The first time a person’s immune system encounters a flu virus, it makes antibodies targeting hemagglutinin .
Could explain why some flu outbreaks cause more deaths and serious illnesses in younger people.
The study was published in the Science journal.