There are guaranteed to be healthy 18 years who've been double-vaxxed and fought off a COVID infection, possibly as recently as right now during the massive Omicron wave. Their near-term risk of winding up dead/in ICU from a potential new COVID infection is effectively zero.
The idea of a blanket mandate that these young people must be immediately boosted regardless of how many times and how recently their immune system has fought off SARS-CoV-2 or what their current antibody levels are is totally unsupportable as science or public policy. We're moving from cloth mask theater to potentially screwing up your immune system and endangering yourself with unnecessary-to-harmful booster theater. Enough.