Project Details

In the last century there were three pandemics (global epidemics) of influenza (1918-1919, 1957-58, 1968-1969) producing very large numbers of clinical cases and large numbers of deaths (an estimated 20-40 million, 1 million and 1 million deaths respectively) as the population had little immunity to the novel influenza viruses involved (H1N1, H2N2, H3N2 respectively). Immunisation programmes delivered in primary healthcare settings have been shown to be acceptable (as evidenced by previous high uptake rates) and effective, and this will therefore be the mainstay of disease prevention in the current influenza pandemic. The new H1N1 influenza vaccination will be targeted at those who are at increased risk of serious illness or death from influenza like illness i.e. young children, older people and those with any of the following underlying medical conditions; chronic renal disease; immunosuppression resulting from disease or treatment; chronic heart disease; chronic lung disease; chronic liver disease including cirrhosis and diabetes mellitus. Frontline health and social care workers will also be prioritised for vaccination.

Observational studies can be used to estimate the effectiveness of healthcare interventions in situations where it is unethical and/or not feasible to mount more rigorous experimental studies; such is the case in the current HIN1 pandemic. Observational studies can also assess the effects of healthcare interventions without influencing the care that is provided or the patients who receive it. 

Results from these studies are generalisable in that they can be used by other countries or regions to help guide public health policy. The inherent novelty of the new H1N1 virus requires that a high degree of vigilance at both the epidemiological and microbiological levels accompanies the implementation of a vaccine programme for the whole population. Policymakers will be reassured if: 1) early evidence can be gathered that the vaccine for H1N1 is widely acceptable as evidenced by high uptake rates and is being distributed by primary care as a priority to health care workers and those at most risk of adverse effects of the virus such as children, the elderly, pregnant women and those deemed to be at-risk on the basis of existing illnesses and 2) if the vaccine is effective in preventing influenza like illness and death.

The setting for this project will be in 40 general practices based throughout Scotland. These practices have about 250,000 people registered with them. By extracting the relevant anonymised electronic patient information from general practice which includes age, sex, illness data and prescribing information and linking this with laboratory data of patients with suspected H1N1 influenza and also information on death from the General Register for Scotland dataset; from this compiled dataset, we will be able to determine the:
1) Uptake of the H1N1 vaccine by the relevant at risk populations i.e. children (<5 years), pregnant women, health care workers, patients with relevant co-morbidities and those >65 years;
2) Reduction in the expected incidence of influenza related serious morbidity and mortality in these at risk groups, since this is the major rationale behind the immunisation policy;
and 
3) Effectiveness of the H1N1 vaccine in the whole population

Permission to use the database for research purposes has been provisionally obtained from the Research Governance Group which oversees use of general practice data. Linkage of similar data to the SMR01 and laboratory data has been previously approved and so we are confident that we will also be able to obtain the necessary approvals from the Information Services Division’s Privacy Advisory Committee (who oversee links to the death data) and the Caldecott Guardian (who oversees the use of the laboratory data) to undertake this work.

Design: Primary Research - a retrospective observational study.

Setting: The Practice Team Information network of 40 general practices covers a five percent representative sample of the Scottish population (n=250,000). These practices receive an annual financial incentive to record all of their practice data electronically [5]. Using the unique Community Health Index number, general practice patient level data will be extracted and linked to the SMR01 catalogue, which comprises of death data from the General Registers Office Scotland and in-patient hospital data for the whole of Scotland and also the Health Protection Scotland (HPS) dataset consists of laboratory confirmed cases of H1N1 influenza from throughout Scotland.

Target population : Patients classified as high risk- incorporating asplenics and the severely immuno-compromised (haematological malignancies and non-haematological malignancies who are currently receiving cancer therapy). Patients who are not at risk will also be analysed.

Health technologies being assessed: The H1N1 pandemic influenza vaccination.

Measurement of outcomes:
- The vaccination uptake in the relevant populations (children (<5 years), pregnant women, health care workers, patients with at risk co-morbidities and those >65 years) recorded by general practice between prior to 1st November 2009;
- Daily consultation of influenza related serious morbidity in vaccinated and unvaccinated patients stratified by at risk populations and 10 year age-bands and sex between 1st August and 1st November 2009;
- Mortality in vaccinated and unvaccinated patients stratified by at risk populations and 10 year age-bands and sex between 1st August and 1st November 2009;
- Mortality and influenza related serious morbidity in vaccinated and unvaccinated patients in the whole population;
- The relative risk of dying from H1N1 influenza calculated according to vaccination status for the target groups - 1st August and 1st November 2009.

Sample size: We plan to recruit 40 practices with a combined list size of approximately 250,000 patients. Approximately 5% (n=13,500) of patients will be aged 0-5 years, 15% (n=37,500) aged over 65 years, and 30% under 65 years will be deemed to be in the at-risk category on the basis of existing illnesses. It is estimated that 10% (n=5,054) of 15-44 year old women will be pregnant and 5% (n=12,500) of people of working age registered with the practices will work for the NHS.