First there was the shortage, then the surplus. Now comes the study.
An epidemiologist from the National Institute of Allergy and Infectious
Diseases led a study that found an unforeseen bias that overstated the
life-saving effects of flu vaccines for the elderly.
[T]he most seriously ill patients in hospitals and nursing homes
did not receive the vaccine, while those who were healthier did. When
the sickest patients subsequently died, the statistics made it appear
that the vaccine was successful at preventing deaths.
Despite this bias, the study notes, flu vaccines still do save lives and the elderly should still get them.