Influenza Vaccination Cuts Deaths by Up to Four Times

Influenza vaccination significantly reduces flu-related morbidity and mortality across all age groups, according to a large-scale Spanish study analyzing data from more than 38 countries and 6.5 million patients.

Published in the European Respiratory Review, the meta-analysis was conducted by the Virology and Innate Immunity Research Group at CEU San Pablo University, Madrid, Spain, and validated using the TriNetX database. It was carried out in collaboration with the National Center for Microbiology of the Carlos III Health Institute, 12 de Octubre University Hospital, and the National Influenza Center of Valladolid.

The analysis confirms that vaccination against the influenza A (H1N1) virus and the influenza B virus (IBV) effectively reduces infection rates and flu-related complications in children aged under 5 years, individuals aged 5-65 years, and older adults aged over 65 years. However, protection against influenza A (H3N2) virus appears lower in older adults, despite being effective in younger children.

Speaking with Univadis Spain, a Medscape Network platform, Estanislao Nistal Villan, PhD, principal investigator of the study and professor of microbiology at CEU San Pablo University, explained the findings. “H3N2 is particularly complex because it has a slightly higher mutation rate than the other two viruses, which may reduce vaccine effectiveness,” he said. “Additionally, it appears to have a higher glycosylation rate and greater sugar addition, which may alter the ability of antibodies to neutralize the virus.”

Overall Effectiveness

Despite higher infection rates, the study concluded that vaccination against H3N2 remains as effective as vaccination against H1N1 and IBV in reducing influenza-related morbidity and mortality across all age groups.

“The parameter of effectiveness can be measured in other ways, not by whether or not the person becomes infected, but by the chances of developing severe flu, entering the ICU, or dying. And that is where the vaccines are effective. All of them were against H1N1, H3N2, and IBV,” Nistal Villan explained.

This study, which compiled data on influenza incidence and severity from articles covering patient data from 2003 to 2023, emphasized that influenza vaccination should focus on preventing serious illness rather than infection. “Vaccination reduces morbidity, hospital admissions, ICU admissions, and, above all, death. Both in people of different ages and in risk groups,” Nistal Villan stated. He noted that influenza is particularly severe in high-risk groups, such as individuals with cardiovascular or neurodegenerative disease. However, “vaccination reduces the risk of death from severe influenza by three to four times,” he concluded.

Nistal Villan received funding from the Spanish Ministry of Science, Innovation and Universities. The authors had no conflicts of interest to declare.

This story was translated from Univadis Spain using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.