In prior studies, an impressive 50 percent reduction in death from any cause had been noted in elderly people who got a flu shot, but some researchers were skeptical of this degree of benefit, suggesting that it may have been the result of the "healthy user effect." The new study supports this line of thinking.
The study included more than 700 elderly people, half of whom had gotten a flu shot and half of whom had not. After controlling for a variety of factors that were largely not considered or simply not available in previous studies, the researchers concluded that any death benefit "if present at all, was very small and statistically non-significant and may simply be a healthy-user artifact that they were unable to identify."
"The healthy-user effect," study chief Dr. Sumit Majumdar of the University of Alberta in Edmonton, Canada explained in a statement, "is seen in what doctors often refer to as their 'good' patients -- patients who are well-informed about their health, who exercise regularly, do not smoke or have quit, drink only in moderation, watch what they eat, come in regularly for health maintenance visits and disease screenings, take their medications exactly as prescribed -- and quite religiously get vaccinated each year so as to stay healthy. Such attributes are almost impossible to capture in large scale studies using administrative databases.