I have no idea why you believe a third dose is just marketing. It is plainly obvious that immunity decreases over time, as is the case for all vaccines against flus and similar.
A booster is the normal way to handle it. If there were a way to avoid it, at least one of the many companies working on this would have created it. And one for the regular flu, too, while they are at it, which has not happened in decades.
A booster is the normal way to handle it. If there were a way to avoid it, at least one of the many companies working on this would have created it. And one for the regular flu, too, while they are at it, which has not happened in decades.