I'm a firm believer in immunization. I bear the proof of its effectiveness on my body: I only got one immunization against smallpox, the second one was usually made ten years after the first one. But that wasn't needed any more - smallpox were gone!
Unfortunately it's not that easy with a fast changing virus, that's why we have to get a flu shot every year. But I'd prefer a shot every few months to contracting corona ;)