Oxford University Press (OUP), Clinical Infectious Diseases, 3(58), p. 319-327
DOI: 10.1093/cid/cit736
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Influenza vaccine effectiveness in preventing medically attended influenza in the 2011–2012 season was modest overall, with low effectiveness against the predominant A (H3N2) virus. This may be related to antigenic drift, but past history of vaccination might also play a role.