Antigenic sin or shift? Not being a biologist I have to rely on the most robust information I can find, our definitions of robust research do not and will likely never align.
I agree that the flu vaccine effectiveness is poor though the combined effectiveness of the four strains vaccinated against was closer to 30% I believe though on of the strains contained was more like the figure you quote.
Particularly in high risk groups the risk of influenza poses a greater risk to health and even with suboptimal matching is seen to be beneficial. Personally I am on the fence, I think the effectiveness will need to improve vastly and quickly.
