Older people are now getting boosters. There seems to be little doubt that they help prevent infection in the short term.
For those not getting boosters, don't fret. The vaccine is working. T-cells, responsible for generally longer term immune response, do not appear to wane, according to this recent article. This may be a reason why the rate of hospitalization does not appear to change over time for vaccinated people even though the rate of infection does (see my recent post about vaccine effectiveness here). T-cells will not stop initial infection but instead are activated once you are infected (this is a simplification. See more here).