Influenza: evidence from Cochrane Reviews

The Cochrane Reviews listed below have summarised data about the benefits and harms of several interventions for preventing and treating influenza. These comprehensive reviews provide valuable information for patients, doctors, and healthcare decision-makers about what steps to take or interventions to use to prevent influenza or aid its treatment.

The reviews are grouped into prevention (physical methods, drugs, vaccines for healthy people, vaccines for people with other illnesses) and treatment (drugs, other treatments).

Preventing influenza: physical methods (e.g. hand-washing, masks, and gloves)

Physical interventions to interrupt or reduce the spread of respiratory viruses

Viral epidemics or pandemics of acute respiratory infections like influenza or severe acute respiratory syndrome pose a world-wide threat. Antiviral drugs and vaccinations may be insufficient to prevent catastrophe. This review assesses the effectiveness of physical interventions, such as hand-washing or wearing masks, to interrupt or reduce the spread of respiratory viruses.

Preventing influenza: drugs, including neuraminidase inhibitors (e.g. Relenza and Tamiflu)

Amantadine and rimantadine for influenza A in children and the elderly

Although amantadine and rimantadine are used to relieve or treat influenza A symptoms in healthy adults, little is known about the effectiveness and safety of these antivirals in preventing and treating influenza A in children and the elderly. This review aims to systematically consider evidence on the effectiveness and safety of amantadine and rimantadine in preventing and treating influenza A in children and the elderly.

Amantadine and rimantadine for influenza A in adults

amantadine and rimantadine have antiviral properties, but they are not widely used due to a lack of knowledge of their potential value and concerns about possible adverse effects. This review aims to assess the efficacy, effectiveness and safety of amantadine and rimantadine in healthy adults.

Neuraminidase inhibitors for preventing and treating influenza in children

During epidemic years, influenza attack rates in children exceed 40%. Options for prevention and treatment include the neuraminidase inhibitors zanamivir and oseltamivir. This review aimed to assess the efficacy, safety and tolerability of neuraminidase inhibitors in the treatment and prevention of influenza infection in children.

Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children

Neuraminidase inhibitors are thought to help reduce the symptoms of influenza with several possible mechanisms proposed. These drugs have been stockpiled with a view to their widespread use in the event of a pandemic; however, the evidence base for this class of agents remains a source of debate. An earlier Cochrane Review documented substantial risks of publication bias of trials of neuraminidase inhibitors for influenza and reporting bias in the published trials and the authors' confidence in their previous conclusions has been subsequently undermined. The January 2012 review updates and merges existing reviews, assessing clinical study reports of placebo-controlled randomised trials, regulatory comments and reviews of the effects of the neuraminidase inhibitors oseltamivir and zanamivir for preventing and treating influenza in all age groups and appraises trial programmes, rather than single studies. [Editorial about this Cochrane Review]

Preventing influenza: vaccines for healthy people

Vaccines for preventing influenza in healthy children

The consequences of influenza in children and adults are mainly absenteeism from school and work. However, the risk of complications is greatest in children and people over 65 years old. This review aims to appraise all comparative studies evaluating the effects of influenza vaccines in healthy children; to assess vaccine efficacy (prevention of confirmed influenza) and effectiveness (prevention of influenza-like illness); and to document adverse events associated with influenza vaccines.

Vaccines for preventing influenza in healthy adults

Different types of influenza vaccines are currently produced worldwide. Healthy adults are presently targeted mainly in North America. This review aims to identify, retrieve and assess all studies evaluating the effects of vaccines against influenza in healthy adults. [Podcast July 2010] Additional resources for this Cochrane Review are also available from the Cochrane Journal Club. [Cochrane Journal Club version]

Vaccines for preventing influenza in the elderly

Vaccines have been the main global weapon to minimise the impact of influenza in the elderly for the last four decades and are recommended worldwide for individuals aged 65 years or older. The primary goal of influenza vaccination in the elderly is to reduce the risk of complications among persons who are most vulnerable. This review assesses the effectiveness of vaccines in preventing influenza, influenza-like illness, hospital admissions, complications and mortality in the elderly. It also aims to identify and appraise comparative studies evaluating the effects of influenza vaccines in the elderly, and to document types and frequency of adverse effects associated with influenza vaccines in the elderly.

Influenza vaccination for healthcare workers who work with the elderly

Influenza rates among healthcare workers are unknown, but may be similar to the general public, and they may transmit influenza to patients. This review aims to identify studies of vaccinating healthcare workers and the incidence of influenza, its complications and influenza-like illness in individuals ≥ 60 in long-term care facilities. [Podcast of the above two Cochrane Reviews February 2010]

Preventing influenza: vaccines for people with other illnesses

Vaccines for preventing influenza in people with asthma

People with asthma may benefit from an influenza vaccine since influenza may exacerbate asthma, but the vaccine may adversely affect lung function. This review examines the evidence on the benefits and harms of using influenza vaccines in people with asthma. [Español PDF]

Influenza vaccine for patients with chronic obstructive pulmonary disease

Influenza infection causes excess morbidity and mortality in people with chronic obstructive pulmonary disease, but there is also the potential for influenza vaccination to cause adverse effects or not to be cost effective. This review looks at the benefits and harms of the influenza vaccine for people with chronic obstructive pulmonary disease.

Influenza vaccine for children and adults with bronchiectasis

Bronchiectasis is a major cause of respiratory morbidity especially in developing countries. In affluent countries, bronchiectasis is increasingly recognised in certain subsections of communities as well as a coexistent disease/comorbidity and disease modifier in respiratory diseases such as chronic obstructive pulmonary disease. Respiratory exacerbations in people with bronchiectasis are associated with reduced quality of life, accelerated pulmonary decline, hospitalisation and even death. Current recommendations for inactivated influenza vaccination includes adults aged 65 years and over, those in residential care and health care workers, and also all adults and children with chronic illness, particularly cardiac and pulmonary diseases. This review evaluates the effects on the severity and frequency of respiratory exacerbations and pulmonary decline, of influenza vaccine as routine management in children and adults with bronchiectasis.

Vaccines for preventing influenza in people with cystic fibrosis

Viral respiratory tract infections in people with cystic fibrosis have a deteriorating effect on their lung function and disease progression. Annual influenza vaccination is therefore commonly recommended for people with cystic fibrosis. This review assesses the effectiveness of influenza vaccination for people with cystic fibrosis.

Influenza vaccination in children being treated with chemotherapy for cancer

Influenza infection is a potential cause of severe morbidity in children with cancer, therefore vaccination against influenza is recommended. However, there are conflicting data concerning the immune response to influenza vaccination in children with cancer and the value of vaccination remains unclear. This review assesses the efficacy of influenza vaccination in stimulating immunological response in children with cancer during chemotherapy, compared with control groups. It also aims to assess the efficacy of influenza vaccination in preventing confirmed influenza and influenza-like illness and/or stimulating immunological response in children with cancer treated with chemotherapy, compared with placebo, no intervention or different dosage schedules. Finally, it aims to determine the adverse effects associated with influenza vaccination in children with cancer.

Treating influenza: drugs, including neuraminidase inhibitors (commonly known as Relenza and Tamiflu)

Amantadine and rimantadine for influenza A in children and the elderly

Although amantadine and rimantadine are used to relieve or treat influenza A symptoms in healthy adults, little is known about the effectiveness and safety of these antivirals in preventing and treating influenza A in children and the elderly. This review systematically considers evidence on the effectiveness and safety of  amantadine and rimantadine in preventing and treating influenza A in children and the elderly.

Amantadine and rimantadine for influenza A in adults

Amantadine and rimantadine have antiviral properties, but they are not widely used due to a lack of knowledge of their potential value and concerns about possible adverse effects. This review aims to assess the efficacy, effectiveness and safety of amantadine and rimantadine in healthy adults.

Neuraminidase inhibitors for preventing and treating influenza in children

During epidemic years, influenza attack rates in children exceed 40%. Options for prevention and treatment include the neuraminidase inhibitors zanamivir and oseltamivir. This review aims to assess the efficacy, safety and tolerability of neuraminidase inhibitors in the treatment and prevention of influenza infection in children.

Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children

Neuraminidase inhibitors are thought to help reduce the symptoms of influenza with several possible mechanisms proposed. These drugs have been stockpiled with a view to their widespread use in the event of a pandemic; however, the evidence base for this class of agents remains a source of debate. An earlier Cochrane Review documented substantial risks of publication bias of trials of neuraminidase inhibitors for influenza and reporting bias in the published trials and the authors’ confidence in their previous conclusions has been subsequently undermined. The January 2012 review updates and merges existing reviews, assessing clinical study reports of placebo-controlled randomised trials, regulatory comments and reviews of the effects of the neuraminidase inhibitors oseltamivir and zanamivir for preventing and treating influenza in all age groups and appraises trial programmes, rather than single studies. [Editorial about this Cochrane Review]

Neuraminidase inhibitors for the treatment of influenza infection in people with cystic fibrosis

Influenza can worsen the course of the disease in people with cystic fibrosis by increasing the risk of pneumonia and secondary respiratory complications. Antiviral agents form an important part of influenza management and include the neuraminidase inhibitors zanamivir and oseltamivir. These inhibitors can limit the infection and prevent the spread of the virus. This review assesses the effects of neuraminidase inhibitors for the treatment of influenza infection in people with cystic fibrosis.

Treating influenza: other treatments

Advising patients to increase fluid intake for treating acute respiratory infections

Acute respiratory infection is a common reason for people to present for medical care. Advice to increase fluid intake is a frequent treatment recommendation. Attributed benefits of fluids include replacing increased insensible fluid losses, correcting dehydration from reduced intake and reducing the viscosity of mucus. However, there are theoretical reasons for increased fluid intake to cause harm. Anti-diuretic hormone secretion is increased in lower respiratory tract infections of various aetiologies. This review seeks to determine the benefit versus harm from increasing fluid intake. In particular, it aims to answer the following questions. (1) Does recommending increased fluid intake as a treatment for acute respiratory infections improve duration and severity of symptoms? (2) Are there adverse effects from recommending increased fluids in people with acute respiratory infections? (3) Are any benefits or harms related to site of infection (upper or lower respiratory tract) or a different severity of illness?

Chinese medicinal herbs for influenza

Influenza is an acute respiratory communicable disease which, during epidemics, can cause high morbidity and mortality. Traditional Chinese medicinal herbs, often administered following a particular theory, may be a potential medicine of choice. This review assesses the effect of Chinese medicinal herbs in preventing and treating influenza, and to estimate the frequency of adverse effects.

Acknowledgements: With thanks to Mike Clarke for comments and edits. 

Image credit: Pasieka/Science Photo Library, M050/1052

Date published: 17 March 2010; updated 18 January 2012.

Contact: Cochrane Editorial Unit (editorial-unit@cochrane.org)