SARS-CoV-2 vaccine research is moving beyond the traditional injection-based approach, with scientists examining whether immunity can be established directly at the surfaces where respiratory viruses first enter the body. A study published in npj Viruses reports that a vaccine based on Newcastle disease virus produced a safe and immunogenic response when delivered through the respiratory tract in ferrets. The findings identify the avian virus as a potential platform for mucosal vaccination against COVID-19 and related coronavirus threats.
Newcastle disease virus is an enveloped virus that primarily affects birds and is not regarded as a major human pathogen. Its biology has made it attractive to vaccine developers because it can be modified to carry genetic information from other viruses. In this approach, the Newcastle disease virus functions as a viral vector: it delivers instructions for SARS-CoV-2 antigens to cells in the respiratory system, prompting the immune system to recognize coronavirus-associated targets without exposing the recipient to infectious SARS-CoV-2.
The study by Pagliarani, Tuling, Pham and colleagues focused on respiratory delivery in a ferret model. Ferrets are widely used in respiratory-virus research because their airways and patterns of viral transmission share important characteristics with those of humans. Although animal models cannot fully reproduce human disease or vaccine responses, they can provide valuable information about how a candidate vaccine behaves in the nose, throat and lungs, where respiratory infection is initiated.
The central significance of the work lies in its delivery strategy. Most licensed COVID-19 vaccines are administered intramuscularly, a route that is highly effective at generating circulating antibodies and protective T-cell responses. However, injection does not always create strong or durable immunity in the mucosal tissues of the upper respiratory tract. A respiratory vaccine is designed to stimulate local defenses, including secretory antibodies and immune cells positioned near the epithelial surfaces that encounter inhaled virus. These responses could help limit infection and reduce the amount of virus available for onward transmission.
According to the report, the Newcastle disease virus vaccine was well tolerated in the ferret model and generated measurable immune responses against SARS-CoV-2. The combination of safety and immunogenicity is an essential early test for any viral-vector platform. A candidate may provoke strong antibody production yet cause unacceptable inflammation, tissue damage or other adverse effects. Conversely, a vaccine may be safe but fail to activate immunity at a level likely to provide meaningful protection. The study’s findings indicate that respiratory administration achieved a favorable balance in the animals examined.
The use of a Newcastle disease virus vector also offers several practical and biological advantages. Because the vector is distinct from the viruses that commonly infect humans, pre-existing immunity against it may be limited in many populations, potentially allowing the vaccine to function efficiently after administration. Its replication properties can also be adapted during vaccine design to improve safety while retaining the ability to stimulate innate and adaptive immune pathways. These features make the platform relevant not only to SARS-CoV-2 but also to the development of multivalent vaccines targeting several respiratory pathogens.
Mucosal immunization presents technical challenges that are not encountered to the same extent with injections. The respiratory tract is protected by mucus, ciliary movement and antimicrobial factors, all of which can remove vaccine material before it reaches target cells. At the same time, excessive activation of local innate immunity could cause irritation or inflammation. An effective formulation must therefore remain sufficiently stable, reach the appropriate tissues and engage antigen-presenting cells without producing harmful reactions. Results in ferrets provide an opportunity to evaluate these issues before a candidate advances to human studies.
The findings should nevertheless be interpreted as evidence from an animal model rather than as proof of human clinical effectiveness. Ferrets can reproduce several aspects of respiratory-virus biology, but differences in anatomy, immune history, dosage, delivery devices and exposure conditions can substantially affect outcomes. Further work will be needed to determine how long the vaccine-induced responses persist, whether they protect against infection or disease after viral exposure, how well they perform against emerging SARS-CoV-2 variants and whether repeated respiratory dosing remains safe and effective.
The study adds to a growing effort to develop vaccines capable of blocking respiratory viruses at their portal of entry. If future research confirms the platform’s safety, durability and protective performance, a Newcastle disease virus-based vaccine could complement existing injectable products rather than replace them. The broader goal is to combine systemic immunity, which helps prevent severe disease, with strong local immunity that may reduce infection and transmission. For now, the ferret results position respiratory-delivered Newcastle disease virus as a promising experimental technology in the continuing search for more effective SARS-CoV-2 vaccines.
Subject of Research: Respiratory-delivered Newcastle disease virus vaccine against SARS-CoV-2 in a ferret model
Article Title: Newcastle disease virus is a safe and immunogenic respiratory-delivered vaccine against SARS-CoV-2 in a ferret model
Article References: Pagliarani, S., Tuling, J., Pham, P.H. et al. Newcastle disease virus is a safe and immunogenic respiratory-delivered vaccine against SARS-CoV-2 in a ferret model. npj Viruses (2026). https://doi.org/10.1038/s44298-026-00217-1
Image Credits: AI Generated
DOI: 10.1038/s44298-026-00217-1
Keywords: Newcastle disease virus, SARS-CoV-2, COVID-19 vaccine, respiratory vaccine, mucosal immunity, viral vector, ferret model, vaccine safety, vaccine immunogenicity, viral science
