Effectiveness of vaccine against pandemic influenza A/H1N1 among people with underlying chronic diseases: cohort study, Denmark, 2009-10

Re: Effectiveness of vaccine against pandemic influenza A/H1N1 among people with underlying chronic diseases: cohort study, Denmark, 2009-10

10 February 2012

Why so little comment about the Danish study of flu vaccine effectiveness in people with chronic diseases? At best the pandemic vaccine was only 49% effective in preventing lab-confirmed disease from pH1N1 after 14 days, and in the first week after vaccination it nearly quadrupled the associated risk of being hospitalized with pH1N1! Furthermore, prior receipt of seasonal flu vaccine alone nearly tripled the associated risk of hospitalization with pH1N1!

This was a large study in an integrated health system that efficiently linked vaccination with outcomes and effectively overcame selection bias. It should prompt us to reconsider national flu vaccination programs, but no one is talking.

Were the authors' conclusions too understated? Have we been distracted by the laboratory bird flu flap? Has the current flu season thus far been mild enough to quiet our passions?

Competing interests: None declared

Allan S. Cunningham, Retired Pediatrician

Cooperstown, NY--USA, Cooperstown, NY

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