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The difficulties of providing influenza immunisation

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VOL: 102, ISSUE: 42, PAGE NO: 25

Terry Hainsworth, BSc, RGN, is clinical editor, Nursing Times

Delays are predicted for delivery of influenza vaccine for this year's immunisation programme. This article outline...

Delays are predicted for delivery of influenza vaccine for this year's immunisation programme. This article outlines the epidemiology of seasonal influenza and prevention by vaccination. It highlights the difficulties faced by vaccine manufactures and healthcare professionals in providing annual immunisation.

The UK Vaccine Industry Group (UVIG) has warned that deliveries of vaccines for this winter's flu campaign are going to be delayed due to problems growing the virus strains. The government has therefore issued a reminder of the target groups for influenza immunisation (nursingtimes.net, 2006).

Epidemiology

Influenza is a respiratory infection caused by the influenza virus and transmitted by droplets of respiratory secretions from person to person.

The influenza virus was first identified in 1933 and there are two main types of influenza virus, known as influenza A and influenza B. Infection from these normally peaks between December and March each year (Umeed, 2001) with influenza A usually causing a more severe illness than influenza B (Health Protection Agency, 2006).

In most cases influenza is not serious but in some individuals it can be more severe and lead to complications, such as bronchitis or secondary bacterial pneumonia. These can be life threatening and may require hospital admission (HPA, 2006).

As many as 3,000 to 4,000 excess deaths are attributable to influenza in the UK each year (Salisbury and Begg, 1996). Also it is thought that deaths due to influenza infection are under-reported as the cause of death on the death certificate is often myocardial infarction or pneumonia (UVIG, 2006).

Influenza vaccine

The influenza vaccine is an inactivated vaccine that contains killed virus. The vaccine stimulates the production of antibodies in the body and when needed provides protection against influenza.

The influenza virus continually changes, with different subtypes circulating each winter so a new vaccine has to be produced annually. Each year samples of viruses from around the world are collected by four WHO reference laboratories in London, Atlanta, Melbourne and Tokyo. The laboratories test how well antibodies made for the current vaccine react to the circulating virus and to new flu viruses.

This process results in the selection of three viruses, two subtypes of influenza A viruses and one influenza B virus, to make up the flu vaccine for the following autumn and winter. Usually one or two of the three virus strains in the vaccine are changed each year. Vaccine production starts in March and continues through the spring and summer.

The WHO predictions produce a good match between the forecast viruses and the actual viruses causing the outbreak. As a result the vaccine gives 70-80% protection (Salisbury and Begg, 1996).

The make-up of the 2006 vaccine was announced in February this year by the WHO. The vaccine contains:

- A/New Caledonia/20/99 (H1N1)-like virus;

- A/Wisconsin/67/2005 (H3N2)-like virus;

- B/Malaysia/2506/2004-like virus.

The influenza A/H1N1 component is unchanged from last year and the B component is the same as the one used in the southern hemisphere vaccine for 2005-2006. This is the seventh year in a row that the A/New Caledonian virus has been included in the vaccine.

This year manufacturers have had difficulty growing one of the virus strains for the vaccine, raising concerns that distribution would be delayed. The production period has been extended to make good the initial shortfall in production.

A statement from the UVIG (2006) in August said that the majority of the vaccine is set to arrive in October and November. Because of possible delays general practices are being advised to prioritise at-risk groups.

Most surgeries should have received details of their revised delivery schedules but if not, UVIG suggests they contact their supplier as soon as possible.

The vaccination programme

Most of the deaths from influenza that occur in the UK are in those who are at higher risk because they have other medical conditions or are elderly. For example, 80% occur in people who are 65 or over (Kassianos, 2001).

Vaccination against influenza reduces the possibility of death as a result of influenza infection by as much as 75% and reduces death from influenza-associated respiratory illness by 43-63% (Unmeed, 2001). Therefore a vaccination programme is important in preventing significant morbidity and mortality in those who are high risk.

Each year the chief medical officer issues advice on identifying those who are at increased risk. For winter 2006 (CMO, 2006) this is anyone aged 65 or over and anyone regardless of age who has:

- Chronic respiratory disease;

- Chronic heart disease;

- Chronic renal disease;

- Chronic liver disease;

- Diabetes requiring insulin or oral hypoglycaemic drugs;

- Immunosuppression.

In addition, vaccination has also been recommended for:

- Those in long-stay residential care homes or other long-stay care (not prisons, young offenders institutions or university halls);

- Carers who are in receipt of a carer's allowance or are the main carer for an elderly person of a person with disabilities whose welfare may be at risk if the carer falls ill;

- All healthcare workers involved in the delivery of care and/or support to patients.

Flu activity reporting

The HPA produces reports through the flu season from October to May. The reports are produced weekly or fortnightly depending on the level of activity. The graphs showing activity give an indication how the rates compare with seasonal norms. The first report will be produced this week.

Clinical data to prepare the reports is gathered from GP surgeries on the number of weekly consultations per 100,000 population for flu-like illness and other acute respiratory illnesses.

The three schemes in England, Wales and Scotland use different methodologies so the consultation rates are not directly comparable between the three countries. In England the rates are based on weekly consultations for new episodes of flu and flu-like illness.

In Wales a detailed case definition is required which may result in fewer cases reported. In Scotland the numbers are higher as they are based on both first and repeat consultations.

Practice implications

Records from last year's immunisation programme (HPA, 2006) show that uptake in those over 65 was high (Fig 1). Uptake in at-risk groups was:

- Chronic respiratory disease - 42%;

- Chronic heart disease - 51%;

- Chronic renal disease - 36%;

- Chronic liver disease - 26%;

- Diabetes - 69%;

- Immunosuppression - 39%.

For a successful influenza campaign it is essential to begin planning clinics as early as January to ensure that sufficient vaccines are ordered and all patients who are at risk have been identified (Skeet, 2005).

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