In equating immunity with prevention it is important to spell out prevention of what. Immunity comprises both short term prevention to infection as well as long term prevention of severe disease consequences. Either as a convalescent or a vaxxed invidual the short term component is on the order of 4 month to a year, and has to do with circulating antibodies titers that can vary considerably from individual to individual. The long term memory component of immunity involves a separate (but related) set of immune cell populations. In some cases this component of immunity memory can last a lifetime.
In this sense there are many parallels between omicron (with omicron perhaps more accurately called cov-3) and measles. Measles is one of the most, if not the most, infectious viruses in humans. In terms of its R number, omicron is either right behind measles or running neck in neck. It's mind blowing. Childhood vaccination against measles has two public health objectives. First, to prevent outbreaks. Second, and perhaps more importantly given the increased severity of measles in adults, vaccination induces that long lasting immune memory component. Especially if Cov-2 and its related offspring increasingly fall under selective pressure to circumvent short-term immunity, vaccination won't do much to temper community transmission. It may be a long time before we are in a position to talk about outbreaks, and who knows what flavor of C-virus we will be dealing with. But the data appears pretty strong that vaxx, particularly after the clean up on aisle 5 that attends infection, induces an extremely diverse set of long term immune memory cell populations that recognize molecular surfaces of Ace2 in a variety of conformations. That data has been linked on this thread. It can be linked again if anybody cares, which i doubt.
I think people should do what they want. But the argument for vaxxing kids as i see it parallels the situation with measles closely. the future is obviously unknowable, but it seems pretty reasonable to think at this point that the next generation will be dealing with periodically re-emergent forms of this virus for the rest of their lives. Their kids may bring it home from school to them. And each time it pops out of the woodworks who knows what it will look like. But, given what we do know, there is a choice that can hopefully give their long term immunity the broadest possible arsenal going forward.