Multicomponent vaccination against seasonal influenza and COVID-19: a strategy to address the continued global burden of disease in adults

Seasonal influenza and SARS-CoV-2 are respiratory viruses that represent a global health concern, causing substantial numbers of hospitalizations and mortality, particularly among high-risk groups, including infants and older adults. Together these associated respiratory diseases and related complications are among the leading causes of morbidity and mortality. Although effective vaccines are available for protection against influenza and COVID-19, vaccine uptake remains below the levels recommended by the World Health Organization (WHO). Increasing vaccination coverage is critical for protecting vulnerable populations and reducing strain on healthcare systems. To improve vaccine uptake, the WHO recommends co-administering influenza and COVID-19 vaccines when epidemiologically justified. A multicomponent vaccine approach in adults could go beyond the current co-administration approach, as it has the potential to streamline delivery, reduce missed vaccination opportunities, and enhance vaccine coverage among individuals at risk. This manuscript reviews the current evidence on multicomponent vaccination for protection against seasonal influenza and COVID-19. We summarize published literature on the potential public health impacts of a multicomponent vaccination approach, discuss associated challenges, and review multicomponent vaccines currently in development. The studies in this review highlight various potential benefits of a multicomponent approach, including simplified dosing, greater vaccination coverage, and reduced disease burden and costs. Healthcare workers expressed a preference for a combination vaccine over standalone influenza or COVID-19 vaccines, indicating a high likelihood of recommending it to patients. Consumers also showed strong interest. For multicomponent vaccination to succeed, key considerations include the optimal timing of administration and appropriate strain selection for both the influenza and SARS-CoV-2 viruses. Promising multicomponent influenza–COVID-19 vaccine candidates currently being evaluated in clinical trials may represent an important advancement in adult immunization strategy, and a meaningful opportunity to strengthen protection against two of the most consequential respiratory pathogens worldwide.