No, a vaccine did not stop the "spanish flu". Although you are correct many people tried creating vaccines for it. We have no reason to believe any of them were successful. Why not? The virus that caused the pandemic was not identified until the early 1930s. In fact instruments in 1920 were incapable of seeing a virus or anything smaller than a bacterium.

Nevertheless, a million or more doses of various vaccines may have been distributed. 500,000 doses of a mixed bacterial vaccine (streptococcal, pneumococcal, staphylococcal, and Pfeiffer's bacilli) developed by E.C. Rosenow at the Mayo Foundation were made available in 1918. Several universities had programs that produced vaccines, and individual physicians published their attempts as well. But again, absolutely no evidence that any of these provided protection against the pandemic of the time.