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3.2 Surveillance

Surveillance is a year-round global activity. Its objective is to monitor the evolution of flu viruses and associated illness to inform recommendations for the annual vaccine, but also in order to detect the emergence of 'unusual' viruses (that may have pandemic potential) as soon as they emerge. The sooner a potential pandemic virus is detected, the sooner control measures can be put in place and the sooner the development of a vaccine can begin. Effective surveillance is vital, not only in detecting the first virus, but also for example, in detecting the first signs of person-toperson transmission. The UK is an integral part of an international network of flu surveillance to which it contributes, and from which it receives, data.

3.2.1 The World Health Organization Global Influenza Surveillance Network

3.2.1 The World Health Organization Global Influenza Surveillance Network

This is an international network of laboratories which provides a mechanism for monitoring flu viruses and detecting the emergence of new viruses with pandemic potential. The World Health Organization network consists of four WHO Collaborating Centres (in Australia, Japan, the USA and the UK), which perform genetic analyses of around 2000 flu viruses each year, and 112 contributing national influenza laboratories in 83 countries, including the UK, which collect more than 175,000 samples from patients with flu-like-illness.

3.2.2 The European Influenza Surveillance Scheme

3.2.2 The European Influenza Surveillance Scheme

This is a collaborative surveillance network within the European Network for the Epidemiological Surveillance and Control of Communicable Diseases and is funded by the European Union. It combines clinical surveillance and reference laboratory reports from 23 European countries, including the UK, allowing flu activity to be monitored across Europe.

3.2.3 UK Health Protection Agency

3.2.3 UK Health Protection Agency

Flu surveillance across the UK is co-ordinated by the Health Protection Agency (an independent body funded by the Department of Health) throughout the year but with a particular focus over the winter months. The agency uses a range of information sources including data on new general practitioner consultations for flu-like illness, laboratory reports and data from the NHS telephone information service NHS Direct, and their equivalents in the other UK countries, to monitor circulating flu virus strains and the illness they are causing. It aims to detect new subtypes of epidemic or pandemic potential.

3.3 Diagnosis

Influenza is essentially a clinical diagnosis, but accurate diagnosis is the backbone of surveillance. It is vital for detecting the emergence of new flu strains, assessing their risk to public health and to monitoring and containing the spread of disease. It can be difficult to distinguish flu from illnesses caused by other respiratory viruses or even bacteria by symptoms alone. There are two methods for confirming the presence of flu infection:

3.4 Vaccines

Vaccination is the mainstay of seasonal influenza control. However, vaccines may not be available during the early stages of a pandemic (see below).

3.4.1 How do vaccines work?

3.4.1 How do vaccines work?

Vaccines are biological agents that stimulate the body to produce antibodies or other immunity. These antibodies are designed to protect the body from the strains of the virus contained in the vaccine. On exposure to the flu virus, the antibodies help prevent infection or reduce the severity of illness. Generally, vaccines reduce infection by around 70-80%, hospitalizations in high-risk individuals by around 60% and deaths by around 40%.

3.4.2 Vaccination against 'ordinary' flu

3.4.2 Vaccination against ordinary flu

Every year, a new vaccine must be developed to protect against the three most prevalent influenza virus strains likely to be circulating that winter. In the UK, vaccination is recommended for those most at risk of serious illness from flu (see Chapter 1, for a list of at-risk groups). Vaccination is also offered to health and social care workers involved in direct patient care. Around 12 million doses of flu vaccine are now administered each year in the UK, covering over 70% of people aged 65 years and over and a substantial proportion of other at-risk groups.

The effectiveness of the vaccine depends on how well the vaccine strains match the circulating strains. The World Health Organization Global Influenza Surveillance Network decides which virus strains are likely to be circulating during the forthcoming flu season and should be covered by the vaccine. The strains in the vaccine are chosen to match as closely as possible the most virulent strains in circulation.

3.4.3 Vaccination during a pandemic

3.4.3 Vaccination during a pandemic

Vaccines also offer the best line of defence in reducing illness and deaths during a flu pandemic. However, currently available flu vaccines are likely to provide little or no immunity in a pandemic situation. A new vaccine must be developed to match the pandemic strain of virus. This work can only begin once that strain has been identified, although preparatory work can shorten the lead time in production.

This means that:

Current vaccine research

The UK, in collaboration with the World Health Organization, is one of the countries leading research aimed at the development of a vaccine against pandemic flu once the pandemic virus is known. This includes the improvement of routine flu vaccine strains and the development of prototype pandemic vaccine strains based on the forecasting of possible genetic changes relevant to a pandemic.

NIBSC in the UK has produced a suitable virus, using the avian flu virus A/H5N1, for the development of an H5N1 vaccine against pandemic flu. If a pandemic strain derived from this virus does not diverge significantly from A/H5N1, this vaccine may prove effective. If a future pandemic virus turns out to be significantly different from this A/H5N1 strain, the vaccine may not offer protection but could speed up the production of an effective pandemic vaccine.

An experimental pandemic vaccine may be available in limited supplies before a definitive licensed vaccine becomes available. This may be used for protection of people at highest risk of infection, for example, laboratory workers.

Why will there not be enough vaccines to go round immediately?

Another constraint to ensuring sufficient vaccine supply during a pandemic is the current manufacturing capacity which is based on the year-on-year use of influenza vaccines for targeted population groups. A vaccine cannot be produced until the virus strain is known. It is likely to take four to six months before quantities of vaccine will become available and then over a period of time. Discussions continue at the international and national level on how to boost vaccine production in the event of a pandemic.

Secondly, it is likely that in a pandemic situation two doses of the vaccine will be required rather than one.

Who would be vaccinated first?

The Joint Committee on Vaccination and Immunisation (JCVI) an independent advisory committee has made provisional recommendations for prioritising groups for vaccination. These recommendations, used in the UK plan, are not final and will continue to be informed by advice from WHO and JCVI, based on the emerging epidemiology of the pandemic and other information.

Groups prioritized for vaccination:

Who will purchase the vaccine?

The Department of Health (England) is responsible for purchasing and supplying a pandemic vaccine on behalf of the whole UK. The Department will liaise with the health departments of Northern Ireland, Wales and Scotland for the supply of vaccines to the devolved administrations.

Who will carry out immunisation?

The precise vaccine formulation, dose and dose schedule will not be known until nearer the time so detailed arrangements for immunisation are not yet established. However, it is likely that people at risk of becoming infected with pandemic flu through their occupations will be immunised at work whilst general practitioners and nurses will play a major role.

Strategic health authorities are responsible for ensuring local pandemic flu contingency plans are in place including the rapid provision of vaccines, once supplies become available.

3.5 Antiviral drugs

Medicines known as antivirals active against flu are the only other major medical countermeasure available. They may be used in the absence of, or as an adjunct to, vaccination.

How do antiviral drugs work?

Antiviral drugs work by preventing the flu virus from reproducing. For treatment, they must be taken within 48 hours of the onset of symptoms in order to be effective. Treatment at this stage can shorten illness by around a day and reduce hospitalizations by an estimated 50%. They must then be taken either before, or within 48 hours of, exposure.

Antiviral drugs are not recommended for everybody. They are available to treat people more at risk of serious illness.

Antiviral drugs for pandemic flu

Antiviral drugs are likely to have an important role in the prevention and treatment of pandemic flu, especially when sufficient vaccine supplies are not available. However, it is important to note the following:

Are there enough antiviral drugs available for everyone during a pandemic?

Antiviral drugs are expensive, take time to manufacture, have a limited shelf life, and will be in high international demand at the time of a pandemic. The UK is building up a stockpile of antiviral drugs against the contingency of a flu pandemic. As with other medicines it will be necessary to use them in the most effective way.

Who will receive antiviral drugs?

The UK plan has identified strategies and prioritized groups for receipt of antiviral drugs. However, since it is impossible to identify with absolute certainty those who would benefit most from antiviral treatment, these recommendations are not final and will be reviewed according to advice from expert bodies on the emerging epidemiology of the pandemic and other information. The priority groups are likely to be:

Who will supply antiviral drugs?

Health service organisations are responsible for local plans to ensure those recommended antiviral treatment receive it within 48 hours of the onset of symptoms. Pharmacists are likely to have a role in the supply of antiviral drugs.

3.6 Social interventions

Non-medical, 'social' or 'social distancing' interventions will be important in delaying or slowing the spread of pandemic flu to allow time for a vaccine to be produced.

These interventions are still under consideration and may be amended pending guidance from the World Health Organization, national advisory bodies and evidence acquired during the pandemic.

Personal interventions

Some basic measures can be taken at the individual level to reduce the risk of infection:

Population-wide interventions

Other interventions at the national level may also be introduced at various stages during the pandemic:

Screening of people entering UK ports

This is unlikely to be effective because of the highly infectious nature of the flu virus. Screening can only detect people who are showing symptoms. Pandemic flu victims may be infectious even before they exhibit symptoms yet would not be detected by port screening systems.

Wearing of masks

The widespread wearing of masks by the general public during a pandemic is unlikely to be effective in preventing people from becoming infected with the virus. However, they may have some limited use for those already infected with the virus in order to prevent them spreading the germs.

Controlling pandemic flu: Summary

• Pandemic flu
• Influenza at the World Health Organisation (opens new window)