The flu vaccine reduces mortality from coinfections

Vaccination against the flu not only protects against the virus but can reduce mortality associated with secondary bacterial infections, according to a study in mice led by the Icahn School of Medicine at Mount Sinai (United States) in which a team from the National Center for Microbiology (CNM) of the Carlos III Health Institute (ISCIII) and groups from the CEU San Pablo University in Madrid participate.

Secondary bacterial infections, such as those caused by Streptococcus pneumoniaeare one of the main causes of serious complications and death during annual flu epidemics in people at risk, such as the elderly and immunosuppressed patients. The work published in the Journal of Virology explains the relationship between the flu virus and these lethal infections and highlights the role of vaccines as a preventive tool.

The results indicate that a single dose of the trivalent inactivated influenza virus vaccine (TIV) has reduced 50% to the 15% Mortality in simultaneous coinfections of viruses and bacteria in mice. In the case of so-called super infections, those that appear only a week after the viral infection, this reduction in mortality has gone from 100 to 50 percent in the murine model.

Vaccination has also achieved reduce viral and bacterial loads and control lung inflammation. Among the immunological changes observed, the massive loss of alveolar macrophages has been avoided, the presence of eosinophils has increased and the infiltration of neutrophils has been reduced, suggesting a more controlled inflammation process than that observed in unvaccinated animals.

Likewise, the vaccine has allowed reduce the production of proinflammatory cytokinesand favored a more balanced humoral response in vaccinated coinfected mice, compared to unvaccinated coinfected ones.

In this way, the results facilitate the understanding of why influenza opens the door to lethal bacterial infections, and suggest that vaccination can change this scenario and significantly improve survivaleven with suboptimal doses of the vaccine, by boosting the immune system response.

The authors of the study, among whom stand out Juan García-Bernalt Diego and Estanislao Nistal Villanfrom CEU, and Javier Arranz-Herrerohave highlighted the importance of expanding research to obtain more data on how influenza vaccination could reduce bacterial complications in humans, reinforcing its role as a key preventive tool.

“This study represents another demonstration of the need to understand how trained immunity works to control the memory of the innate immune system,” concluded the researcher at the CNM-ISCIII and the Icahn School in New York, Jordi Ochando.