The burden of influenza complications in different high-risk groups: a targeted literature review

Abstract

Objectives:

The objective was to review the published literature on seasonal influenza to assess the differences between complications and mortality rates for those adults at high risk of influenza complications, including the resource use of those hospitalized with influenza complications.

Methods:

A targeted literature review was performed using electronic database keyword searches, specific inclusion criteria, quality rating of the reviewed full-text articles and abstraction of data to present published evidence on the incidence, complication rates and health service use associated with clinical influenza in different adult high-risk groups including those who are aged 65 years and older or those with different chronic underlying medical conditions.

Results:

Key findings for incidence rates of clinical influenza were that incidence rates are similar among people with chronic cardiovascular or respiratory comorbidity, and may be higher in those with allogeneic stem cell transplants compared to those with autologous transplants. Rates of hospitalization and/or pneumonia or lower respiratory tract infection for those with chronic conditions or those who are immunocompromised are substantially higher than those in people over age 65 but without additional high-risk factors. A person who is hospitalized and has a laboratory-confirmed influenza diagnosis has a probability of intensive care unit admission of between 11.8–28.6% and of death of between 2.9–14.3%.

Conclusions:

These findings indicate that although the burden of influenza varied across high-risk groups, it also varied widely across studies within a single high-risk group. A key finding was that those over 65 years of age but without additional high-risk factors had a low risk of influenza complications. A limitation of the review is that most of the studies of hospitalized patients did not present outcomes data separately by high-risk group and only limited data were identified on rates of hospitalization or lower respiratory tract infection for most high-risk groups. Information about influenza complication rates and resource use, including influenza vaccines, chemoprophylaxis and/or treatment strategies for different high-risk groups, is needed to evaluate new interventions.

Keywords::

• Influenza
• Complications
• High-risk
• Hospitalization
• Intensive care unit
• Mechanical ventilation
• Mortality

Abbreviations::

• CASP, Critical Appraisals Skills Programme
• COPD,chronic obstructive pulmonary disease
• HIV, human immunodeficiency virus
• ICU, intensive care unit
• ILI, influenza-like illness
• LCI, laboratory-confirmed influenza
• LRTI, lower respiratory tract infection
• US, United States

Transparency

Declaration of funding

This review was sponsored by Janssen-Cilag, Horsham, PA, USA.

Declaration of financial/other relationships

JM has disclosed that she has received funding from Janssen to perform the literature review and to prepare this paper. She performs similar projects for many other pharmaceutical companies. MK, SL, and GH-T have disclosed that they are employed by Janssen, which is developing a compound for the treatment of influenza in high-risk groups.

Authors’ contributions

MK, SL, and JM designed the literature review study, and JM performed the literature review. MK, GH-T, and JM jointly developed the outline for the paper, interpreted the results of the literature review, and wrote sections of the paper. All authors reviewed drafts of the paper and reviewed and approved the final paper.