Next time someone comes for a regular flu shot think: heterosubtypic immunity.
What does that mean?
Vaccinations give narrow immunity.
Natural infections give wider immunity (heterosubtypic immunity).
Being infected by influenza A – naturally – give protection against realetd species i.e. possibly H1N1.
But being vaccinated stops you from getting natural infection and hence you are left without this additive protective effect i.e. not good if it’s a killer pandemic.
Is this confirmed?
Experimental evidence is pointing to it (animal studies). Whether it holds true is unclear as no one has checked to see if the chidren who died from a pandemic strain such as H1N1 had more regular Influenza A vaccinations then those who did not.
If you want read more here.