The virus spreads among people who are out and about at school and work; it is then brought home, where it kills the age extremes—infants and the elderly—who are at the end of the transmission chains. This is also the reason, incidentally, that immunizing the elderly, while it will reduce their deaths, does not have much effect on the actual course of the epidemic. Immunizing working-age people helps break chains of transmission through social networks and can be much more effective in preventing deaths on a population level
