When the health authorities say that they don't recommend it because benefits do not outweigh risks they usually mean that the benefits aren't at least 2 magnit

When the health authorities say that they don't recommend it because benefits do not outweigh risks they usually mean that the benefits aren't at least 2 magnitudes (100 times) bigger than the risks. Vaccination usually is highly beneficial, but as one ages the benefit does diminish. Agencies don't want to be stuck with vaccines which have large side effects.