INFLUENZA VIRUSES AND VACCINES: HOW VACCINE EFFECTIVENESS STUDIES INFORM THE BENEFITS OF INFLUENZA VACCINATION
Abstract
Influenza is a preventable disease, and vaccination remains the most effective strategy to reduce seasonal influenza-related illness and death, especially among high-risk groups. Currently, three types of influenza vaccines are licensed for use: inactivated, live-attenuated, and recombinant haemagglutinin vaccines. Studies on vaccine effectiveness are essential for assessing the real-world benefits of these immunizations. Although influenza vaccines can significantly lower the disease burden, their overall effectiveness is moderate—typically estimated at 40% to 60% when the vaccine strains closely match circulating viruses. This review examines influenza viruses and vaccines while highlighting the role of vaccine effectiveness studies in evaluating the benefits of immunization. Overall, these vaccines effectively decrease morbidity and mortality across all age and risk groups, with particularly strong benefits observed in young children and older adults. Nonetheless, their effectiveness is influenced by factors such as the age of the recipient, the match between vaccine strains and circulating viruses, egg-adaptation changes during production, and an individual’s vaccination history.
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