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The ability of inactivated influenza vaccines to significantly reduce morbidity and mortality in a year from ‘the flu’ is unknown and data confirming influenza vaccine safety are limited, according to a new report in the British Medical Journal. A comprehensive analysis of influenza vaccine studies conducted around the world and published in the medical literature revealed that there is not enough scientific evidence to support annual influenza vaccination of all children, adults and the elderly. This is according to Tom Jefferson, MD, who coordinated the analysis for the Cochrane Collaboration.

"There is a big gap between policies promoting annual influenza vaccinations for most children and adults and supporting scientific evidence" said Jefferson, "..given the significant resources involved in annual mass influenza vaccination campaigns, there is urgent need for re-evaluation of these strategies”.

The new report entitled, "the prevention of seasonal influenza—policy versus evidence" examines the complex characteristics of seasonal influenza viruses (as opposed to pandemic viruses), which change their antigenic configuration from year to year as well as vary in prevalence – and so on their sensitivity to a vaccine. The report points out that influenza vaccine "performance" depends in part on the closeness of the match between forecasted circulating influenza viruses and the actual viruses selected for that influenza season's vaccine to act against. When the influenza viruses chosen for the vaccine closely resemble the circulating viruses in a given year, the vaccine is more protective. Another very important component is the amount of influenza circulating: the higher the circulation the higher the effectiveness of the vaccines. Unfortunately no one can predict this and the amount of "flu-like illness" circulating is no predictor as it is different from real influenza.

According to the report, a major problem with evaluating influenza vaccine performance is potential confusion between respiratory infections caused by influenza viruses and those caused by other viruses (the ‘flu’). Misdiagnosis of influenza in patients with respiratory infections caused by other viruses can lead to a gross overestimation of the true impact of influenza on death and illness from respiratory infections in a given influenza season.

"The best way to judge how well influenza vaccines (made using inactivated viruses) perform is to sum up all data from known studies into systematic reviews" said Jefferson "systematic reviews of large datasets from several decades are likely to provide more reliable information on the performance of influenza vaccine performance over time”. And on how appropriate the available vaccine is.

The newly published report assesses the evidence from systematic reviews, mainly Cochrane reviews, and concludes that existing scientific evidence for influenza vaccine safety and efficacy relies on research that is methodologically flawed with selection bias, confounders and heavy reliance on non-randomized studies. Too few clinical trials have been carried out, especially in the elderly. In addition, past studies have not addressed vaccine safety adequately while indicating that use of inactivated influenza vaccine has only a modest or no effect on preventing influenza in children and the elderly.

Some of the summaries of Cochrane reviews that Tom Jefferson has been involved in

Healthy adults

There is not enough evidence to recommend universal vaccination against influenza in healthy adults

Influenza is an acute, viral respiratory infection with symptoms of headache, fever, muscle pain, cough and a runny nose. It spreads easily and can cause serious illness. New strains develop regularly. Each year, the World Health Organization recommends which strains to include in vaccinations for the next 'season'. People considered 'at risk' of complications may be offered vaccination. This review found that vaccinating healthy adults not at risk of complications reduced their chances of developing flu-like illness by only a quarter, and the number of working days lost by less than half a day. Vaccination had no reported relevant adverse effects.

V Demicheli, D Rivetti, JJ Deeks, TO Jefferson. Vaccines for preventing influenza in healthy adults. The Cochrane Database of Systematic Reviews 2004, Issue 3. Art. No.: CD001269.pub2. DOI: 10.1002/14651858.CD001269.pub2.

Healthy children

Nasal spray vaccines are better than injected vaccines at preventing influenza in children; neither were particularly good at preventing influenza-like illness

This review assessed how good influenza vaccines were in preventing 'flu' in children who are normally healthy. Nasal spray vaccines made from weakened influenza viruses, were better at preventing illness caused by the influenza virus than injected vaccines made from killed virus. Neither type was particularly good at preventing 'flu-like illness' caused by other types of viruses. A large amount of information was collected comparing reactions in children who had received vaccines with those who had not. However, the vaccine types could not be compared because of the different ways the data were collected and presented in the studies. It was not possible to analyse the safety of vaccines from the studies due to the lack of standardisation in the information given. Very little information was found on the safety on inactivated vaccines, the most commonly used, in young children.

S Smith, V Demicheli, C Di Pietrantonj, AR Harnden, T Jefferson, NJ Matheson, A Rivetti. Vaccines for preventing influenza in healthy children. The Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD004879.pub2. DOI: 10.1002/14651858.CD004879.pub2.

Elderly people

The review looked at whether vaccines prevented seasonal influenza and its complications in people aged 65 or older

Influenza vaccination of elderly individuals is recommended worldwide as people aged 65 and older are at highest risk for complications, hospitalisations and deaths from influenza. The review looked at evidence from experimental and non-experimental studies carried out over 40 years of influenza vaccination. Seventy-one studies were included and were grouped first according to study design and then to setting (community or long-term care facilities). Studies were further stratified by level of viral circulation and vaccine matching. The results of the review 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 are the most commonly used influenza vaccines. Best effectiveness of current vaccines in preventing clinical illness and its complications was seen in long-term care facilities (for example nursing homes) where vaccines prevented about 45% of pneumonia cases, hospital admissions and influenza-related deaths. Effectiveness in elderly individuals residing in open community settings is modest, irrespective of outcome or study design: about 25% of vaccine efficacy in preventing hospitalisation from influenza or respiratory illness. The apparent good effect on all-cause mortality (a less specific outcome) comes from observational studies only and may reflect differences between vaccinated and non-vaccinated groups (such as socio-economic characteristics, health status, behavioural attitudes) rather than a real effect of vaccination. The public health safety profile of the vaccines appears to be acceptable.

D Rivetti, T Jefferson, R Thomas, M Rudin, A Rivetti, C Di Pietrantonj, V Demicheli. Vaccines for preventing influenza in the elderly. Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD004876.pub2. DOI: 10.1002/14651858.CD004876.pub2.

People with asthma

Influenza vaccine now seems unlikely to worsen asthma, but research is needed to determine whether asthma attacks are prevented by influenza vaccination

Influenza (flu) is a highly infectious disease, caused by viruses. Influenza has been thought to cause asthma attacks. Newly published research suggests that the vaccine against influenza is unlikely to precipitate asthma attacks for a few days after the vaccine is used. Few trials have been carried out in a way that tests whether asthma attacks following influenza infection (as opposed to following the vaccination) are significantly reduced by having influenza vaccination, so uncertainty remains in terms of how much difference vaccination makes to people with asthma.

CJ Cates, TO Jefferson, AI Bara, BH Rowe. Vaccines for preventing influenza in people with asthma. The Cochrane Database of Systematic Reviews 2003, Issue 4. Art. No.: CD000364.pub2. DOI: 10.1002/14651858.CD000364.pub2.

People with Cystic fibrosis

Influenza vaccine is effective for people with cystic fibrosis (CF) without causing serious complications, but there is no evidence on whether it can prevent lung damage

People with CF have blocked airways resulting in frequent respiratory infections. Viral infectious diseases like influenza (the ‘flu') can worsen lung damage, therefore annual influenza vaccination is often recommended. This review found several relevant studies using influenza vaccine. Vaccination does result in an immune system response to the types of influenza used in the vaccine. However, this response may not result in protection against influenza infection or lung damage. Adverse effects were not severe or more common with particular types of vaccines. There is no evidence to show if regular influenza vaccine is beneficial to people with CF.

Vaccines for preventing influenza in people with cystic fibrosis. The Cochrane Database of Systematic Reviews 2000, Issue 1. Art. No.: CD001753. DOI: 10.1002/14651858.CD001753.

People with chronic obstructive pulmonary disease

Despite the almost universal recommendation that people with chronic obstructive pulmonary disease (COPD) should receive an annual influenza vaccination, very few randomised controlled trials have evaluated the effect of influenza vaccination in these patients. This review looks at six studies in COPD patients and a further five in elderly or high risk patients, a proportion of whom had chronic lung disease. It shows that there is now some evidence from randomised trials that inactivated influenza vaccine indeed decreases "flare ups" of COPD, especially those that are related to the influenza virus itself.

The inactivated influenza virus vaccine is given intramuscularly and is associated with an increase in local side effects such as pain at the site of injection. This is short-lived, not serious and is outweighed by the long term benefit of the vaccine. The inactivated virus vaccine does not cause influenza or any significant worsening of COPD.

Influenza vaccine for patients with chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD002733.pub2. DOI: 10.1002/14651858.CD002733.pub2.

The Cochrane Library

As long as you can go online, everyone can read the plain language summaries and abstracts of Cochrane reviews.

Here is a good way of accessing them!

Index of reviews:

http://www.cochrane.org/reviews/

Click on a review (blue) and you will be able to see the plain language summary and abstract

[A protocol is a review under development]

Overviews of consumer summaries of Cochrane reviews

CCNet is busy working with the Cochrane Complementary Medicine Field to develop overviews that give summaries of reviews using complementary therapies in a range of health areas. We will have them ready for you to comment on before the end of the year.

Cochrane Consumer Network (CCNet)

Newsletters

CCNet newsletter are published every four months and are full of information for those who are interested. The most recent was published in January 2007 (http://www.cochrane.org/newslett/). We also send out newsletters through our e-mail discussion list: e-mail ccnet-contact@cochrane.de for information.

Cochrane meetings

Cochrane Centres, are located across the world. Many centres plan local Contributors’ Meetings. These meetings generally have sessions aimed at consumers and are a good way of finding out more about The Cochrane Collaboration. You can view a calendar of these and other Cochrane events here:

The Cochrane Calendar - http://www.cochrane.org/news/calendar.htm

Events of significance to consumers:

XV International Cochrane Colloquium to be held in Sao Paulo, BRAZIL, 21 to 25 October, 2007

XIV International Cochrane Colloquium was held in Dublin IRELAND, 23 to 26 October, 2006

The Colloquium provided the opportunity for people involved in the work of CCNet and the Collaboration to meet face to face.

The reports for the Annual General Meeting held in Dublin

Administrator (Word doc)

CCNet-Contact (Word doc)

Ethics meeting (Word doc)

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Current Pictures

consumers from around the world

Some active international consumers in CCNet

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Consumers wanted

People who are interested in commenting on protocols and reviews in preparation for publication on The Cochrane Library are invited to contact us (E-mail: ccnet-contact@cochrane.de). We are also appreciative of receiving consumer comments on existing protocols and reviews.

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Other information

CCNet is taking a more active role in working with Cochrane Review Groups to develop plain language summaries of reviews.

If you would like to know more about this, e-mail ccnet-contact@cochrane.de for further information.

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