MIT looks like they're trying inhaled vaccines for cancer: <a href="https://news.mit.edu/2021/vaccination-inhalation-0319" rel="nofollow">https://news.mit.edu/2021/vaccination-inhalation-0319</a><p>And several others are looking at CoV too: <a href="https://pubmed.ncbi.nlm.nih.gov/33749491/" rel="nofollow">https://pubmed.ncbi.nlm.nih.gov/33749491/</a><p>I guess nasal vaccines have been around for a while but the inhaled thing is still pretty new(ish) and from what I could read on some scattered short mentions in other reading, it's not really very widely used? I may be wrong on that, and can't find a great citation.
An open source inhaled vaccine was one of the first vaccines to be publicly promoted. I've always wondered how it would fare in RCTs, as it would be interesting if an open, unregulated vaccine design proposed relatively early in the pandemic became a model for coronavirus vaccines going forward.
What is the main reason that inhaled vaccines are not in use today for flu for example? Is there some new technological breakthrough for delivery that was needed?