Vaccines for preventing seasonal influenza and its complications in people aged 65 or older

Jefferson T, Di Pietrantonj C, Al-Ansary LA, Ferroni E, Thorning S, Thomas RE

Published Online:

February 17, 2010

Influenza vaccination of elderly individuals is recommended worldwide as people aged 65 and older are at a higher risk of complications, hospitalisations and deaths from influenza. This review looked at evidence from experimental and non-experimental studies carried out over 40 years of influenza vaccination. We included 75 studies. These were grouped first according to study design and then the setting (community or long-term care facilities). The results are mostly based on non-experimental (observational) studies, which are at greater risk of bias, as not many good quality trials were available. Trivalent inactivated vaccines are the most commonly used influenza vaccines. Due to the poor quality of the available evidence, any conclusions regarding the effects of influenza vaccines for people aged 65 years or older cannot be drawn. The public health safety profile of the vaccines appears to be acceptable.

Abstract (click to read)

Background:

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.

Objectives:

To assess the effectiveness of vaccines in preventing influenza, influenza-like illness (ILI), hospital admissions, complications and mortality in the elderly.
To identify and appraise comparative studies evaluating the effects of influenza vaccines in the elderly.
To document types and frequency of adverse effects associated with influenza vaccines in the elderly.

Search strategy:

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Acute Respiratory Infections (ARI) Group's Specialised Register (The Cochrane Library 2009, issue 4); MEDLINE (January 1966 to October Week 1 2009); EMBASE (1974 to October 2009) and Web of Science (1974 to October 2009).

Selection criteria:

Randomised controlled trials (RCTs), quasi-RCTs, cohort and case-control studies assessing efficacy against influenza (laboratory-confirmed cases) or effectiveness against influenza-like illness (ILI) or safety. Any influenza vaccine given independently, in any dose, preparation or time schedule, compared with placebo or with no intervention was considered.

Data collection and analysis:

We grouped reports first according to the setting of the study (community or long-term care facilities) and then by level of viral circulation and vaccine matching. We further stratified by co-administration of pneumococcal polysaccharide vaccine (PPV) and by different types of influenza vaccines. We analysed the following outcomes: influenza, influenza-like illness, hospital admissions, complications and deaths.

Main results:

We included 75 studies. Overall we identified 100 data sets. We identified one RCT assessing efficacy and effectiveness. Although this seemed to show an effect against influenza symptoms it was underpowered to detect any effect on complications (1348 participants). The remainder of our evidence base included non-RCTs. Due to the general low quality of non-RCTs and the likely presence of biases, which make interpretation of these data difficult and any firm conclusions potentially misleading, we were unable to reach clear conclusions about the effects of the vaccines in the elderly.

Authors' conclusions:

The available evidence is of poor quality and provides no guidance regarding the safety, efficacy or effectiveness of influenza vaccines for people aged 65 years or older. To resolve the uncertainty, an adequately powered publicly-funded randomised, placebo-controlled trial run over several seasons should be undertaken.

This record should be cited as:

Jefferson T, Di Pietrantonj C, Al-Ansary LA, Ferroni E, Thorning S, Thomas RE. Vaccines for preventing influenza in the elderly. Cochrane Database of Systematic Reviews 2010, Issue 2. Art. No.: CD004876. DOI: 10.1002/14651858.CD004876.pub3

Assessed as up to date:

October 7, 2009

PEARLS - Practical Evidence About Real Life Situations (click to read)

Clinical question:

How effective are vaccines in preventing influenza, influenza-like illness, hospital admissions, complications and mortality in the elderly (65 years or older)?

Bottom line:

There was insufficient evidence for the efficacy or effectiveness of influenza vaccines for elderly people, irrespective of setting, outcome, population and study design. Trivalent inactivated vaccines were the most commonly used influenza vaccines. The public health safety profile of the vaccines appeared to be acceptable. Until such time as the role of vaccines for preventing influenza in the elderly is clarified, more comprehensive and effective strategies for the control of acute respiratory infections should be implemented. These should rely on several preventive interventions that take into account the multi-agent nature of influenzalike illness and its context (such as personal hygiene, provision of electricity and adequate food, water and sanitation).

Caveat:

The results were mostly based on non-experimental (observational) studies, which were at greater risk of bias, as not many good quality trials were available (only one randomised controlled trial). Studies done in residents of care homes often indicate the inevitably improvised nature of efforts to study the effect of vaccination during an epidemic. The resident population is usually more homogeneous than that in the community: older, with similar viral exposure and risk levels.

Context:

Influenza vaccination of elderly individuals is recommended worldwide, as people aged 65 and older are at a higher risk of complications, hospitalisations and deaths from influenza. In the year 2000, 40 out of 51 high-income or middle-income countries recommended vaccination for all persons aged 60 or 65 or older.¹ 1. van Essen GA. Vaccine 2003;21:1780–5.

Cochrane Systematic Review:

Jefferson T et al. Vaccines for preventing influenza in the elderly. Cochrane Reviews, 2010, Issue 2. Article No. CD004876. DOI: 10.1002/14651858.CD004876.pub3. This review contains 75 studies involving over 2.45 million participants.

Authored by:

Brian R McAvoy

Cochrane Primary Health Care Field

Health topics:

Infectious disease > Respiratory infections > Influenza

Lungs & airways > Respiratory infections > Influenza

Cochrane Summaries

Independent high-quality evidence for health care decision making

Vaccines for preventing seasonal influenza and its complications in people aged 65 or older

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