Over a thousand healthy adults between the ages of 18 and 64 who worked full time at a large manufacturing firm either received a flu shot or a placebo injection of sterile saline prior to two consecutive influenza seasons. Sounds like a good deal. The authors report no more serious adverse effects of vaccination than some muscle soreness. So, aside from the cost of the vaccine itself, getting a flu shot didn t lead directly to any extra medical expense or time away from work. For older and infirm folks, however, the complications of a bout with influenza are likely to be more severe and more expensive, which is why we can still strongly recommend, even from a purely economic point of view, that this population be immunized every year.
Healthy people are another matter.
The data from this study were subjected to what is called a sensitivity analysis, which showed that the higher the incidence of influenza the more universal immunization makes economic sense. Scientists can predict with some accuracy which will be the rare pandemic years of very high rates of influenza based upon how different one year s strain of virus is from those of the preceding years. The more drastically the virus has changed during the off-season, the fewer people s immune systems will recognize it and the more widespread the infection. Most of the time, though, it just doesn t pay to attempt to vaccinate all healthy adults. This is one of those years, which is fortunate, because we don t have enough vaccine for everybody anyway.