Hospitalization and risk of death due to influenza among vaccinated and unvaccinated patients. A 5-year study in the northeastern Mexican population

In Mexico, seasonal influenza epidemics results in substantial mortality and burden to healthcare resources. The country`s health authority provides vaccination to children <5 years old; adults >60 years of age; those aged 5–60 years with risk factors. Inclusion of school-aged children and adults until 59 years of old with no risk factors in the vaccination program would be highly beneficial. A prospective cohort surveillance study was conducted between the influenza seasons of 2014–2015 and 2018–2019 at the Dr. José Eleuterio González University Hospital. The primary outcome was need for hospitalization in vaccinated and unvaccinated patients with ILI or seasonal influenza. Secondary outcomes included outpatient management, admission to the ICU, and mortality during hospitalization among vaccinated and unvaccinated participants. 361patients (37.44%) had a confirmed influenza diagnosis. Being vaccinated made it more probable to be treated as an outpatient (p = .0001). For unvaccinated patients, the risk for hospitalization (OR = 1.70), ICU admission (OR = 8.46) and in-hospital death (OR = 27.17) was higher. Fifty-two patients died due to complications related to seasonal influenza or ILI, and none of them were vaccinated. Most subjects were between 18 and 49 years old. Influenza vaccination significantly reduced hospitalization, need for ICU admission, and in-hospital mortality in a 5-year study from Monterrey, Mexico.