Herd immunity in an office or church....

So, using flu shots as an example from which to kinda extrapolate.... I've got a coworker who is one of those very rare folks who does have some sort of an allergic reaction to the flu. No big deal, he just doesn't get his flu shot every year. That leaves him with some heightened risk of getting the flu, but when the rest if us in the office get our flu shots, that lessens the likelihood the flu will get a foothold in the office and lessens the likelihood he'll be exposed. By me getting my flu shot, I'm not only helping myself, I'm also helping cover my buddy (some of this is maybe related to the issue of how individual rights interact with responsibilities to groups). Frankly, my buddy is a guy my age who seems to be in great health, so even if he got the flu, it probably wouldn't be all that major a life event.... But what about at a church or someplace, full of babies and elderly folks who maybe can't have some vaccine for some even more difficult disease, or whose immune systems may not be firing on all cylinders.... It could maybe be a bigger deal.