Advocating mucosal immunization: A global need in a viewpoint from China.

Human mucosal immunization is expected to afford protection against infection and reduce transmission by generating anti-infective immunity at the mucosal entry site of viruses and bacteria. Nasal or oral administration has the advantage of being needle free and self-administered, thereby improving compliance and coverage of large populations. In China, the experience of COVID-19 has promoted substantial efforts in the development of nasal vaccinations in the general health protection strategy. The hurdles we are facing in the development of mucosal vaccines, however, come from the still limited knowledge of the mechanisms controlling mucosal immunity in different anatomical locations and in response to different pathogens/vaccines. Identifying and filling the knowledge gaps in order to develop effective and safe mucosal immunization strategies requires global collaboration, not only at the scientific level but, most importantly, by engaging public and private health organizations, governments, and regulatory authorities. We have highlighted here some of the crucial issues in mucosal immunization and provided suggestions for the way forward toward a global preparedness effort to prevent infectious diseases and ensure vaccine equity.