Seasonal Influenza A H1N1pdm09 Virus and Severe Outcomes: A Reason for Broader Vaccination in Non-Elderly, At-Risk People.

Publisher: Public Library of Science Country of Publication: United States NLM ID: 101285081 Publication Model: eCollection Cited Medium: Internet ISSN: 1932-6203 (Electronic) Linking ISSN: 19326203 NLM ISO Abbreviation: PLoS One Subsets: MEDLINE

Original Publication: San Francisco, CA : Public Library of Science

Influenza A Virus, H1N1 Subtype/*isolation & purification ; Influenza Vaccines/*therapeutic use ; Influenza, Human/*complications ; Influenza, Human/*prevention & control; Acute Disease ; Adolescent ; Adult ; Age Factors ; Aged ; Aged, 80 and over ; Antiviral Agents/therapeutic use ; Hospitalization ; Humans ; Influenza A Virus, H1N1 Subtype/drug effects ; Influenza A Virus, H3N2 Subtype/drug effects ; Influenza A Virus, H3N2 Subtype/isolation & purification ; Influenza, Human/diagnosis ; Influenza, Human/drug therapy ; Middle Aged ; Oseltamivir/therapeutic use ; Pneumonia/etiology ; Pneumonia/virology ; Respiratory Distress Syndrome/etiology ; Respiratory Distress Syndrome/virology ; Retrospective Studies ; Risk Factors ; Seasons ; Shock, Septic/etiology ; Shock, Septic/virology ; Treatment Outcome ; Young Adult

Background: Recent pandemics of influenza A H1N1pdm09 virus have caused severe illness, especially in young people. Very few studies on influenza A H1N1pdm09 in post-pandemic periods exist, and there is no information on the severity of both seasonal influenza A(H1N1) and A(H3N2) from the same season, adjusting for potential confounders, including vaccine.
Methods and Results: We performed a retrospective observational study of adults hospitalized during the 2014 season with influenza A(H1N1) or A(H3N2). All patients underwent the same diagnostic and therapeutic protocol in a single hospital, including early Oseltamivir therapy. We included 234 patients: 146 (62.4%) influenza A(H1N1) and 88 (37.6%) A(H3N2). A(H1N1) patients were younger (p<0.01), developed more pneumonia (p<0.01), respiratory complications (p = 0.015), ARDS (p = 0.047), and septic shock (p = 0.049), were more frequently admitted to the ICU (p = 0.022), required IMV (p = 0.049), and were less frequently vaccinated (p = 0.008). After adjusting for age, comorbidities, time from onset of illness, and vaccine status, influenza A(H1N1) (OR, 2.525), coinfection (OR, 2.821), and no vaccination (OR, 3.086) were independent risk factors for severe disease.
Conclusions: Hospitalized patients with influenza A(H1N1) were more than twice as likely to have severe influenza. They were younger and most had not received the vaccine. Our findings suggest that seasonal influenza A(H1N1) maintains some features of pandemic viruses, and recommend wider use of vaccination in younger adult high-risk patients.
Competing Interests: The authors have declared that no competing interests exist.

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0 (Antiviral Agents)
0 (Influenza Vaccines)
20O93L6F9H (Oseltamivir)

Date Created: 20161111 Date Completed: 20170622 Latest Revision: 20220408

20231215

PMC5104455

10.1371/journal.pone.0165711

27832114