The case for immunizing everyone against the flu:
There are several advantages to broadening the range of people to be given flu shots. Because influenza carries substantial risk of requiring hospitalization, giving more people shots will certainly decrease the annual U.S. hospitalization rate and death rate, even though the vaccine isn't perfect—about 25 percent of the time, it fails partly or completely. There is also a secondary benefit: People who have been immunized are much less likely to pass the disease on to others who are unprotected or incompletely protected, a phenomenon called "herd immunity." That's the main reason for the push to immunize all children through age 18—those hacking and spewing youngsters are influenza's version of Typhoid Mary.