There have been several attempts at developing intranasal COVID-19 vaccines, all of them have had disappointing results so far (mostly that the immunity waned p

There have been several attempts at developing intranasal COVID-19 vaccines, all of them have had disappointing results so far (mostly that the immunity waned pretty quickly, if I remember correctly). It would be far more convincing if the authors explicitly acknowledged that in the abstract, and gave a good reason why they think their approach is more promising.