Factors associated with uptake of seasonal and pandemic influenza vaccine among clinical risk groups in the UK: An analysis using the General Practice Research Database
Highlights
► At 40%, uptake of pandemic influenza vaccine in clinical risk groups was low. ► Among the same individuals, uptake of seasonal influenza vaccine was 61%. ► Uptake was associated with age, region, BMI and history of Guillain Barré syndrome. ► Better uptake was observed when entire age groups were recommended for vaccination. ► More needs to be done to increase flu vaccination in clinical risk groups.
Introduction
Influenza is an acute respiratory disease that commonly occurs following infection with influenza viruses. In many individuals the disease is self-limiting with patients experiencing the classic symptoms of influenza (such as fever, sore throat and cough) followed by recovery within one to two weeks. However, in some individuals infection can result in the development of more serious complications such as pneumonia, respiratory failure and death. Individuals with the following underlying health conditions are known to be at a particularly high risk of suffering from these more serious symptoms [1], [2]: asthma, chronic obstructive pulmonary disease (COPD), chronic heart disease, chronic kidney disease, diabetes, chronic liver disease, stroke/transient ischaemic attack, central nervous system degeneration, and immunosuppression. These health conditions are therefore considered ‘clinical risk groups’ for seasonal influenza; individuals in these groups are recommended for vaccination during annual influenza immunisation programs in countries throughout the world [3], [4], [5], [6], [7], [8].
In the early stages of the 2009/10 H1N1 pandemic, epidemiological evidence suggested that individuals in seasonal influenza clinical risk groups were also among those at the highest risk of complications following H1N1 infection [9]. This led a number of public health organisations, including the World Health Organisation, to recommend that they be one of the groups prioritised for vaccination in mass H1N1 immunisation campaigns [9], [10], [11]. Consequently, in many countries, including the UK, all individuals in seasonal influenza clinical risk groups were recommended to receive both seasonal influenza vaccine (SIV) and pandemic influenza vaccine (PIV) during the 2009/2010 influenza season.
High vaccination coverage is vital to the success of any vaccination campaign. Annual SIV coverage varies widely across Europe with the majority of countries reporting uptake rates of less than 50% among clinical risk groups [12]. Uptake rates have been shown to vary by a range of factors such as: age [13], [14], [15], [16], [17], [18], sex [15], [17], [18], [19], [20], [21], chronic illness [20], [21], socioeconomic factors [15], [16], [18], [20], [22] and ethnicity [20], [21], [23], [24]. In the UK, uptake rates among those in clinical risk groups aged <65 years have ranged from 40% to 48% over the last 5 years [13]. Surveys conducted during the 2009/2010 H1N1 pandemic revealed that in many countries there was a widespread public perception that the pandemic was not serious or that PIV was not safe [25]. Such perceptions may have decreased PIV uptake substantially, and indeed coverage data from the UK and the US suggest that while uptake of SIV did not change in 2009/2010, it was considerably higher than that of PIV [14], [26], [27], [28]. In this study we have estimated uptake rates and factors predictive of uptake of both PIV and SIV among clinical risk groups in UK general practice during the 2009/2010 influenza season.
Section snippets
Materials and methods
This study was carried out using the UK General Practice Research Database (GPRD). The GPRD is a primary care database containing the anonymised records of ∼7.8% of the UK population. Patient data that is routinely available in the database includes demographic details, diagnoses and symptoms leading to hospital admissions, referrals to specialists, laboratory tests, prescriptions issued by the GP, pregnancies, contraception, immunisations, hospital discharge summaries, hospital clinic
Results
A total of 708,609 patients were included in our study population. Population characteristics are given in Table 1. The overall PIV uptake rate was 40.3% and the SIV uptake rate was 61.3%. Of the study population, 65.3% had a record of vaccination with at least one of the two influenza vaccines. 36.3% of these had a record of vaccination against both PIV and SIV, while 4.0% were vaccinated with PIV-only and 25.0% with SIV-only. These exclusive rates varied widely across age groups (Fig. 1).
Discussion
Except for in young children, the uptake of SIV in clinical risk groups during the 2009 UK pandemic vaccination campaign far exceeded that of PIV. Several factors including age, number of underlying health conditions and history of GBS were found to be predictive of both pandemic and seasonal influenza vaccine uptake.
One of the main strengths of this study was the large sample size from a well validated primary care database. A limitation of using such a database for this study is that
Acknowledgements
This study is based in part on data from the Full Feature General Practice Research Database obtained under licence from the UK Medicines and Healthcare products Regulatory Agency and covers the data collection time period up to July 2010. However, the interpretation and conclusions contained in this report are those of the authors alone. The authors would like to acknowledge the use of the UK National Grid Service in carrying out this work.
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