Nasal vaccines are one spray ahead in pandemic prevention

Prof. Chen, let’s start with the basics: What are the key immune advantages of nasal vaccines?

Prof. Honglin Chen: For respiratory viruses such as SARS-CoV-2 and influenza viruses like H5N1, nasal vaccines offer a unique immunological advantage: they provide mucosal immunity, which can help limit viral transmission. For the majority of the population already vaccinated with intramuscular vaccines against respiratory viruses, a nasal vaccine booster could enhance protection by establishing robust mucosal immunity, thereby improving defenses against reinfection.

How does the platform trigger both mucosal and systemic immunity?

Chen: Our vaccine is developed using a live attenuated influenza viral vector from which the immune modulator NS1 has been removed. Immunization with this vaccine via nasal spray would stimulate an immune response in the upper respiratory tract tissue, inducing mucosal immunity characterized by IgA production and the formation of tissue-resident memory T cells. Should the nasal vaccine be formulated in an aerosolized form, it has the potential to reach the lungs and elicit a strong systemic immune response as well.

How could nasal vaccines be rolled out in national or global pandemic response plans?

Chen: When a pandemic emerges, it typically begins with localized outbreaks before spreading globally. Controlling transmission early in the outbreak phase is critical. Nasal vaccines offer a strategic advantage in this context: by inducing mucosal responses that limit viral replication and slow transmission, they can help contain outbreaks at their source. With advancements in stockpiling technologies for intranasal vaccine and coordinated global efforts through organizations like CEPI, deploying such vaccines to outbreak areas during the initial stages could prevent localized outbreaks from escalating into full-blown pandemics.

Which laboratory tools are most useful for monitoring immune responses to nasal vaccines?

Chen: Mucosal immunity markers like IgA provide a practical and accessible way to monitor immune responses elicited by nasal vaccines. The COVID-19 pandemic has highlighted the critical need for vaccines capable of inducing both mucosal and systemic immunity, which are essential for controlling viral transmission and preventing severe disease. As multiple nasal vaccine platforms advance in development, standardized immune correlates – such as mucosal IgA levels and tissue-resident memory cells – are being established to evaluate their efficacy and durability.

From a translational research perspective: What’s needed to bring nasal vaccines from the lab to large-scale public use?

Chen: Nasal vaccines must demonstrate high safety and strong immunogenicity. Advancing technologies to optimize intranasal delivery efficiency, coupled with rigorous clinical trials, will greatly accelerate their transition from laboratory research to widespread public implementation.

Could companion diagnostics – like personalized immune profiling – help tailor nasal vaccine strategies?

Where do you see the role of nasal vaccines in a "One Health approach" to zoonotic threats?

Chen: The "One Health framework" offers a long-term plan to address zoonotic threats. Take avian influenza as an example: nasal vaccines could be strategically deployed to disrupt viral transmission between wild birds and domestic poultry. By interrupting this interspecies spillover pathway, we may significantly reduce outbreaks of high-concern strains like H5N1.