Nonspecific: The infected cells produce interferon curtails virus replication in the adjacent respiratory epithelial cells.

Interferon also spreads enters to the circulation for 2-4 day and activates splenic NK cells.

Specific and memory:

Local cytotoxic T cells abort the production of virus and neutralising antibody prevents virus spread so the infection may be stopped by 6 days. The viruses which depend much on Tc to clear them eg RSV and herpesviruses are those for which vaccination has been least successful.