[jonbxx]

There seems to be some confusion between immunity and sterilising immunity here. The current COVID vaccines are reasonably good at raising immunity as measured in antibody levels and immune cell (T and B cell) responses. They might not recent infection but certainly shorten the length and severity of the disease.

Sterilising immunity prevents infection. For, this, you need antibodies at the infection sites, namely the nose, throat and lungs. The current vaccines are not very effective here. To get sterilising immunity, you need to vaccinate at the potential infection sites. Vaccines which are good at this include polio, smallpox, nasal flu (flumist) It is a huge challenge to make vaccines that work at the sites of infection as these can be quite a harsh environment. If you want to do something quick or ‘good enough’, injectables are the way forward.