> But ANTIBODY LEVELS ARE NOT THE POINT. With intranasal booster to complement intramuscular vacination for respiratory diseases what you're doing is recruiting

> But ANTIBODY LEVELS ARE NOT THE POINT. With intranasal booster to complement intramuscular vacination for respiratory diseases what you're doing is recruiting specialized immune cells to become resident in the upper respiratory mucosa. Let's be clear: that's the goal, not the reality. There is no such intranasal vaccine, and your understanding of IgA/IgG/IgM/etc. is incomplete, because even though these different antibody types are associated with different tissues, it's not a categorical thing. Likewise, it's not like T- and B-cells never make it to the mucosa -- the fundamental issue is that neither form of immunity stays ramped to 11 forever, and cellular immunity takes time to spin up post-infection. To a first approximation: antibodies ramp up quickly and decline quickly, and cellular responses ramp up more slowly, and last longer. When you get infected with a respiratory pathogen, the IgA levels in your nasal mucosa spike early in part because that's the tissue the virus encounters first. If the virus lives long enough to make it elsewhere in the body, it encounters IgG/IgM and ultimately, T- and B-cells. Researchers have been chasing this idea that they can cause persistent cellular immune responses in the nasal mucosa for decades, but there's no good reason to believe it will ever happen. > I'm waiting on an approved intranasal vaccine in the USA before I stop wearing N95s in public and non-home indoor spaces (and limiting my time in them). This is not going to work. You are going to get it. If you have been vaccinated with two doses of the current vaccines and are not severely immunocompromised (e.g. currently undergoing a bone-marrow transplant), you are as well-protected as you are ever going to be. > I really, really wish vaccine development for sars-cov-2 was still a priority. I will emphasize this again: the current vaccines work. You are putting your life on hold while waiting for (effectively) a cure to the common cold. This is not remotely guaranteed to happen in your lifetime. Get two doses -- or more if you like (though there's no evidence for it) -- and be confident that you've done everything practical you can do to reduce your risk.