Novel vaccine strategies to induce respiratory mucosal immunity: advances and implications

Rapid advances in vaccine technology are becoming increasingly important in tackling global health crises caused by respiratory virus infections. While traditional vaccines, primarily administered by intramuscular injection, have proven effective, they often fail to provide the broad upper respiratory tract mucosal immunity, which is urgently needed for first-line control of respiratory viral infections. Furthermore, traditional intramuscular vaccines may not adequately address the immune escape of emerging virus variants. In contrast, respiratory mucosal vaccines developed using the body's mucosal immune response mechanism can simultaneously establish both systemic and mucosal immunity. This dual action effectively allows the respiratory mucosal immune system to function as the first line of defense, preventing infections at the entry points. This review highlights the efficacy of respiratory mucosal vaccines, including innovative delivery methods such as nasal and oral formulations, in enhancing local and systemic immune barriers. Notably, respiratory mucosal vaccines offer potential advantages in protecting against emerging virus variants and maintaining long-term and multidimensional immune memory in the upper respiratory tract. In addition, a combination of intramuscular and respiratory mucosal delivery of vaccines largely improves their coverage and effectiveness, providing valuable insights for future vaccine development and public inoculation strategies.