"Most existing vaccines are prepared from an attenuated version of the pathogen or from inactivated disease-causing organisms or a suitable part of it e.g. a toxin. However, often the antigen to which the immune system responds is a relatively small number of amino acids or peptide."
https://www.who.int/teams/health-product-policy-and-standards/standards-and-specifications/vaccine-standardization/synthetic-peptide-vaccines
"Intranasal vaccines are administered in the nose instead of in the arm."
https://www.verywellhealth.com/intranasal-covid-19-vaccines-5116889
"Coronavirus can spread through the eyes — just as it does through the mouth or nose — through virus particles sprayed from the mouth or nose of an infected person, according to Frank Hwang, MD, ophthalmologist and cornea service director at Loma Linda University Health."
https://news.llu.edu/health-wellness/covid-19-and-your-eyes
"If successful, a new kind of vaccine - a nasal mist that requires no needle - promises to do all that by providing the special kind of coronavirus immunity people need to stop shuttling this virus around.
"An intranasal vaccine could help bring an end to the pandemic and help give us true control over SARS-CoV-2 by limiting infection and transmission," said Marty Moore, the CEO of Meissa Vaccines"
https://news.yahoo.com/nasal-covid-19-vaccine-could-131135817.html
The best protection against COVID-19 could be a vaccine delivered through the nose, according to new paper
https://medicalxpress.com/news/2022-09-covid-vaccine-nose-paper.html