You're making a fundamental assumption that if you prevent people from getting COVID now, we can make it go away permanently.
Looking at historical knowledge, we get flu every single year. Even after a vaccine, people still get flu.
Drawing on experience, what you have to do is regulate the rate of people getting COVID to keep it at a manageable level.
What the public and politicians are hoping is we lock down for 3 weeks, the rate goes to zero, end of story. There's only been one disease in the history of mankind that that's worked (smallpox). Everything else has stayed around, and continued killing.