A recent study presented a mixed picture.
It found that the antibody response of current vaccines could fail against variants. However, a second immune response in the form of killer T cells -- which attack already infected cells and not the virus itself -- remained largely intact.
Several startups are working on developing shots centred on T cells in hopes of producing a jab that would not only provide protection against new virus strains already on the loose, but also variants that don't yet exist.
Alexis Peyroles heads up French biotech firm OSE Immunotherapeutics, which is developing a vaccine that targets T cells that has just begun clinical trials.
"It could offer several years of protection," he told AFP.
Another French firm, Lyon-based Osivax, is also working on a T cell shot, promising a "universal" vaccine that would be effective against any potential variant.