Intranasal vaccines for SARS-CoV-2: From challenges to potential in COVID-19 management

Graphical abstract Unlike conventional Coronavirus 2019 (COVID-19) vaccines, intranasal vaccines display a superior advantage because the nasal mucosa is often the initial site of infection. Preclinical and clinical studies concerning intranasal immunization elicit high neutralizing antibody generation and mucosal IgA and T cell responses that avoid severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in both; the upper and lower respiratory tract. A nasal formulation is non-invasive with high appeal to patients. Intranasal vaccines enable self-administration and can be designed to survive at ambient temperatures, thereby simplifying logistical aspects of transport and storage. In this review, we provide an overview of nasal vaccines with a focus on formulation development as well as ongoing preclinical and clinical studies for SARS-CoV-2 intranasal vaccine products.