BROADLY protective influenza vaccines could provide baseline protection against pandemic strains before matched vaccines become available.
Researchers have proposed integrating pandemic preparedness into routine seasonal influenza vaccination by developing vaccines capable of generating broader immune responses. The proposed “Before Day One” approach aims to provide partial protection against emerging pandemic influenza viruses while maintaining reliable protection against seasonal disease.
Broadly Protective Influenza Vaccines Target an Early Protection Gap
Current pandemic preparedness strategies largely depend on developing strain matched vaccines after a novel influenza virus emerges. Manufacturing and deploying these vaccines takes time, creating a period during which population immunity may be limited.
The proposed strategy would use the established annual influenza vaccination program to build some degree of pandemic protection before an outbreak begins. Modeling cited by the authors suggests that vaccine timing can be as important as efficacy, with earlier deployment of a moderately effective vaccine potentially producing greater public health benefit than delayed use of a more effective product.
Even a 10% reduction in infections during the first pandemic wave could help blunt transmission and preserve healthcare capacity. Reducing early infections could also slow pandemic progression, providing additional time to develop, manufacture, and distribute a strain matched vaccine.
Conserved Influenza Targets Could Expand Protection
Development efforts could focus on conserved regions of influenza viruses that change less extensively between strains. Candidate targets include hemagglutinin, neuraminidase, and internal proteins capable of stimulating T cell responses.
Rather than prioritizing one vaccine platform or antigen, the proposed approach focuses on clinical outcomes. Broadly protective influenza vaccines would need to maintain effective seasonal protection while demonstrating the potential to meaningfully reduce severe outcomes from novel pandemic viruses.
For clinicians, such vaccines could eventually offer advantages beyond pandemic preparedness. Broader immune responses may reduce vulnerability to seasonal strain mismatch, limit year to year variation in influenza vaccine effectiveness, and potentially reduce severe illness.
Pre-pandemic efficacy trials against an unknown future strain are not possible, however. Developers would therefore need to establish relevant immune markers and use animal models and other evidence to infer likely protection against emerging viruses.
A seasonal vaccine capable of providing both routine influenza protection and baseline pandemic coverage could strengthen preparedness without requiring a separate vaccination program. The authors argue that continued development of broadly protective influenza vaccines could therefore offer benefits during ordinary influenza seasons while providing an important first layer of defense when a pandemic strain emerges.
Reference
Jayashankar L et al. Protection Before Day One: advancing broadly protective seasonal influenza vaccines with pandemic coverage. Vaccine. 2026;93:129188.
Featured Image: Pormezz on Adobe Stock.
