Influenza Virus-Related Critical Illness

Prevention, Diagnosis, Treatment

Eric J. Chow; Joshua D. Doyle; Timothy M. Uyeki


Crit Care. 2019;23(214) 

In This Article

Prevention and Vaccination

Influenza vaccination is recommended each fall for all persons aged > 6 months in the U.S. and should continue as long as influenza viruses are circulating in the community. Previously unvaccinated children aged 6 months through 8 years require two doses 1 month apart. Since influenza vaccine effectiveness (VE) to prevent medically attended illness varies from year-to-year by vaccine strain, age, prior immunity, and immune function, some vaccinated individuals can become symptomatic with influenza virus infection. However, several studies have reported influenza vaccine effectiveness in reducing illness severity, including reducing severe illness in persons aged > 65 years,[39] and reducing in-hospital mortality and ICU admissions for those aged 18–49 years and > 65 years compared to unvaccinated individuals.[40] One study reported that duration of ICU hospitalization was reduced a half-day in patients aged 50–64 years who had received influenza vaccination compared with unvaccinated patients.[41] A study across all age groups in Spain reported influenza VE of 58% in reducing the risk of severe influenza requiring hospitalization.[42] A Southern Hemisphere study reported influenza VE of 82% in reducing influenza-associated ICU admissions among adults[43] while a study in Spain showed an adjusted influenza VE of 23% in preventing ICU admission and death.[44]

Despite the benefits of influenza vaccination, there continues to be low vaccine coverage among adults admitted to the ICU who often have a high prevalence of high-risk comorbidities.[45,46] In children, low influenza vaccination coverage has also been reported among those admitted to pediatric ICUs, even among those with underlying high-risk conditions.[47] Full influenza vaccination was shown to result in a 74% reduction in pediatric ICU admissions compared to unvaccinated or partially vaccinated influenza patients.[47] Furthermore, one study showed that influenza VE was 65% in reducing the risk of mortality in children aged 6 months to 17 years in the U.S..[48] These data further emphasize the benefits of influenza vaccination in reducing severe influenza complications, especially in high-risk persons.