Eurosurveillance - Volume 13, Issue 43, 23 October 2008

Influenza is among the infectious diseases with the highest incidence and associated serious morbidity and mortality that can be prevented by vaccination.

A cross-sectional survey was undertaken with the European Union (EU) Member States and Norway and Iceland to describe seasonal influenza immunisation in the 2006-7 season, in particular to identify country-specific recommendations for risk groups, obtain vaccine uptake information and allow comparison with global recommendations. A standardised questionnaire was completed electronically by each country's project gatekeeper. Of the 29 countries surveyed, 28 recommended seasonal influenza vaccination for older age groups (22 for those aged > 65 years), and in one country vaccine was recommended for all age groups. All countries recommended vaccinating patients with chronic pulmonary and cardiovascular diseases and most countries advised to immunise patients with haematologic or metabolic disorders (n=28), immunologic disorders (n=27) and renal disease (n=27), as well as residents of long-term care facilities (n=24). Most countries recommended vaccination for staff in hospitals (n=25), long-term care facilities (n=25) and outpatient clinics (n=23), and one-third had such recommendations for workers in essential (n=10), military (n=10) and veterinary services (n=10) and poultry industry (n=13). Eight countries recommended vaccine for pregnant women; and five advised to vaccinate children (with age limits ranging from 6 months to 5 years). Twenty countries measured influenza vaccine uptake among those aged > 65 years (range 1.8%-82.1%), seven reported uptake in healthcare workers (range 14%-48%) and seven assessed coverage in persons with underlying medical conditions (range 27.6%-75.2%). The data provided by this study can assist EU states to assess and compare their influenza vaccination programme performance with other countries. The information provides a comprehensive overview of policies and programmes and their outcomes and can be used to inform joint discussions on how the national policies in the EU might be standardised in the future to achieve optimal coverage. Annual surveys could be used to monitor changes in these national policies.

In order to understand motivations and barriers to vaccination, and to identify people's intentions to get vaccinated for season 2007-8, influenza vaccination coverage was assessed in the United Kingdom (UK) from 2001 to 2007. Between 2001 and 2007 representative household surveys were performed by telephone interview with 12,143 individuals aged 16 or older. The overall influenza vaccination coverage rate dropped non-significantly from 25.9% in 2005-6 to 25.0% in 2006-7 (p=0.510). In the elderly (≥65 years) the rate decreased from 78.1% to 65.3% (p=0.001), and the odds ratio of being vaccinated compared to those not belonging to any of the risk groups targeted by vaccination decreased from 36.6 to 19.9. Healthcare workers and chronically ill persons had odds ratios of 2.0 and 15.5, respectively. The most important reason for getting vaccinated was a recommendation by the family doctor or nurse, and this was also perceived as the major encouraging factor for vaccination. No recommendation from the family doctor was the main reason for not getting vaccinated. A total of 38.4% of the respondents intended to get immunised against influenza in 2007-8. From 2001 to 2006 a slightly increasing trend (p for trend across seasons <0.0001) in vaccination coverage was observed in the UK, but in 2006-7 the rates returned to the level of 2004-5. Less media attention to the threat of avian influenza after 2005 may have contributed to the recent decrease of vaccination rates.

Seasonal influenza is widely regarded as a continuing threat to public health, with vaccination remaining the principal measure of prophylaxis. In 2003, the World Health Organization issued targets for influenza vaccine coverage in the elderly of at least 50% by 2006 and 75% by 2010, endorsed by the European Parliament in two resolutions in 2005 and 2006. However, a number of European public health systems lack mechanisms to assess progress in influenza vaccine uptake. The European Vaccine Manufacturers group (EVM) undertook a Europe-wide survey of vaccine distribution over the last five seasons (between 2003 and 2008) to provide baseline data from which vaccination trends may be extrapolated. The survey data showed that the dose distribution level per capita in the 27 EU countries increased from 17% in 2003-4 to 20% in 2006-7; this growth was not maintained in the season 2007-8. Even without information on which age or risk groups received the vaccine, an immunisation rate of approximately 20% of the whole population falls short of the public health goal by more than half: an estimated 49% of the total population fall into risk groups recommended to receive the influenza vaccine in Europe. These data provide the only systematic review of vaccine dose distribution across Europe from a uniform source. Although they represent an important baseline parameter, age- and risk-group related vaccine uptake data with sufficient detail are needed to assist public health policy decision making, immunisation planning and monitoring. In light of this situation, and to support the improvement of immunisation rates across the EU, EVM aims to provide dose distribution data for each influenza season to assist Member States in the implementation of local immunisation policies.

In France, annual seasonal influenza vaccination has been recommended since 2000 for patients suffering from chronic respiratory diseases, including asthma. Since 1988, each year from September to December, a free influenza vaccination voucher is sent by the French Public Health Insurance authorities to patients with chronic respiratory disease, including severe asthma. In November 2006, this measure was extended to all asthmatic patients, irrespective of asthma severity. The present paper examines the 2006-7 influenza vaccination coverage rate (VCR) in 433 asthmatic children aged 6 to 17 years (mean age: 9.5 years; male: 61%) who consulted a paediatric pulmonologist between March and September 2007 in eight hospitals throughout France. The influenza VCR was 15.7% for the 2006-7 season (13.9% for the 2005-6 season and 10.9% for the 2004-5 season). General practitioners vaccinated 72.1% of the children. 'Lack of information' (42%) was the most frequently reported reason for non-vaccination. Vouchers (received by 39.6% of the children) significantly increased the VCR (31% versus 5.9%; p<0.001). In France, in 2006-7, the influenza VCR in asthmatic children was far below the national public health objective (at least 75% for the year 2008). Concerted action is needed to improve the influenza VCR in asthmatic children.

Estimating influenza vaccine effectiveness (IVE) early in the season helps measuring the consequences of a mismatch between the vaccine and the circulating strain and guiding alternative or complementary interventions. The European Centre for Disease Prevention and Control is funding a project to develop pilot studies to monitor IVE in the Member States (MS) of the European Union and European Economic Area (EU/EEA) during seasonal and pandemic influenza. To identify key methodological and practical issues in developing protocols for pilot studies, we conducted a survey among EU/EEA MS, a literature review on IVE methods, and consultations of experts. The survey and literature review highlighted the variety of the data sources used to estimate IVE and the difficulty to interpret data on IVE, which varies with age, risk group, outcome specificity and virus-vaccine mismatch. We also found that negative and positive confounding can bias IVE. The experts consultations lead to the following recommendations: to measure IVE in the same population in various seasons; to control for positive/negative confounding (including pre- and post-influenza season IVE estimates); and to include laboratory confirmation as outcome in various study designs. In the 2008-9 influenza season, two cohort studies using general practitioners' databases and six case control studies will be piloted in EU/EEA MS and will adhere to the above recommendations. The pilot studies will be the basis for the development of robust methods to monitor IVE in EU/EEA MS.

This paper summarises the scientific evidence supporting selection of risk groups that would benefit from annual seasonal influenza immunisation in European Union (EU) countries. Risk groups are defined restrictively as persons in Europe at higher than average risk of adverse outcomes should they be infected with seasonal influenza and for whom use of vaccine is demonstrated to be effective in reducing the risk of those outcomes. Existing evidence indicate that older people and those with chronic disease are at higher risk of severe adverse outcome and that immunisation reduces this risk. There is thus good scientific evidence for routinely offering annual immunisation to all older people (at least those aged 65 years and older), and people with certain groups of chronic medical conditions. We estimated that these two groups account for between 19% and 28% of the population of EU countries. Thus in 2006, an estimated 84 million older people aged 65 years and over and 41 million people younger than 65 years of age with chronic conditions were living in these countries. There is also strong evidence for immunising staff caring for patients belonging to these two risk groups in residential (care home) settings in order to protect the patients. There are as yet no strong data on whether or not immunising other healthcare workers and carers protect patients though immunisation of healthcare workers can be justified on occupational health grounds. At present the scientific evidence for immunising other suggested risk groups, notably children and pregnant women is not strong for Europe though equally there is no evidence against immunising these groups.