Boosters alone aren’t enough to prevent the spread

Of course not but they vastly reduce the risk of severe complications (I’m not up to date with the latest research but the figure I remember is >90%). Vaccinations boost the immune system, they aren’t impenetrable force fields.

and people who don’t get the vaccine aren’t the only ones who are at risk of getting sick.

For people suffering from more severe symptoms, there is now very good medication available to aid in recovery.