Most Generation-1 vaccines have a flaw.... simply because these target the "Spike Protein." Think what changes mostly with the variants? - The spike protein.
Some developers went for "Inactivated Vaccines" - eg China, India etc. Theoretically these should perform better and should have an edge over the other mRNA or viral vector methods. However, the inactivated vaccines has low efficacy and no one has really explained why.
So experts believe that the long term solution will not be inactivated vaccines, even though inactivated virus vaccines have an edge in initiating a T-cell response.
Hence Generation-2 covid vaccine research is on. Many believe these should target at least a part of the genetic code of the virus itself.
The only other option is to design an "Anti-Viral drug" that works... The new US administration placed funding for this.