You can catch wuflu more than once. Pretty much all coronavirus types you can become reinfected. Which is why the cold and influenza will probably never be eradicated. There's tonnes of documented cases where people have it multiple times, but this is also why the vaxx will not save anything. At the very best it might help to mitigate more serious symptoms in at risk populations, but it seems more than likely it will have little effect on anything in the public health situation.