Multiple vaccines have not been tested, but immunology suggests they would be safe (using the same adeno-virus would likely be less effective since your body would pre-empt spike production). One possible hypothesis for why Sputnik (which it self is a succession of two different adeno-virus laden spike protein generators) is less effective is that it (unlike Moderna, Pfizer, J&J) does not appear to use a stabilized Spike protein, which makes the immune response it generates more susceptible to this substitution. They key is what parts of the artificial vaccine spike you develop antibodies for, as to how effective the vaccine is for a variant since much of the active portion of the protein is unchanged.
However, since both Moderna and Pfizer are testing mRNA "booster" vaccines specifically for the SA variant, you might just wait for that. They don't have an adeno-virus vector that could be pre-empted by immune response.
However, since both Moderna and Pfizer are testing mRNA "booster" vaccines specifically for the SA variant, you might just wait for that. They don't have an adeno-virus vector that could be pre-empted by immune response.