‘Tackle chlamydia in primary care’
In this series GPs put their burning questions on a clinical topic to an expert – this week Dr Doug Fleming answers questions from Dr Peter Stott
l An avian flu virus pandemic is unlikely this year but a pandemic within three years is likely
l Annual vaccination boosts immunity for those strains included previously as well as introducing new virus antigenic material
l Egg hypersensitivity and a history of Guillain-Barré syndrome are the only absolute contraindications to the vaccine
l Use of anti-viral drugs will be determined by the Department of Health if and when a pandemic emerges
‘A pandemic within three
years is a more likely prospect'
1. What is the likelihood of a pandemic of flu this year? What are the emergent strains?
The threat of a pandemic from an avian flu virus arises because humans have been infected by it. It does not spread between humans and therefore in its present form it is not a pandemic virus.
This H5N1 virus has been around for about two years but it has not yet evolved into a pandemic strain. It is probably unlikely to develop so fast that we might experience a pandemic this winter, but a pandemic within three years is a more likely prospect.
2. How strongly should we be recommending vaccination to children – and those with IgA deficiency?
Children in recognised risk groups (asthma, congenital cardio-respiratory diseases, and those whose immune state is compromised by disease or because of the use of immune suppressant drugs) should be vaccinated.
Influenza vaccines used in the UK contain inactivated virus material and are not a threat to those with impaired immune
3. Carers have been included as an at-risk group this year – eligible for vaccination. GPs find it difficult to define the word ‘carer'. All parents are carers. So too are most middle-aged people who keep an eye on their elderly relatives. How do you interpret the definition of carer?
The definition of a carer is not clear. Many persons who could be considered carers are aged over 65 or have a risk condition and should be vaccinated in their own right. Furthermore, you may be a carer for a short period of time and the definition only applies to you for that limited period.
On the other hand you may be the partner of someone with a risk condition, but are not in a risk group. We therefore have to view this in a commonsense manner. If you are closely linked (usually principal carer or partner ), living with (or having daily contact with) and caring for someone at particularly high risk from flu, you should consider yourself a carer.
Patient risk in this context particularly includes persons with advanced COPD or heart disease, persons undergoing radio- and chemotherapy as part of a cancer management programme, and persons in the terminal stages of disease.
These latter persons, even if vaccinated, may not mount an adequate immune response. Having a partner with a risk condition is not a sufficient reason to be vaccinated as a carer.
4. From year to year, the strains of virus included in the vaccine may not change very much. Patients notice this and bring in articles from the internet. How should we advise them when they say they had that strain last year?
The vaccine contains three virus strains which are chosen from circulating viruses in the previous winter. Some of the constituents may not change very much.
Protection is limited to the strain types included in the vaccine and does not last for long periods.
As well as introducing new virus antigenic material, annual vaccination boosts immunity for those strains which have been included previously.
5. Many patients say they have had reactions to the immunisation. How common is this and which of these are contraindications to further vaccination?
The only side-effect attributable to influenza vaccination observed is local soreness at the injection site (in one major placebo-
controlled trial, 17 per cent in the treated and 7 per cent in the placebo group).
You cannot get flu from the vaccine but if you are vaccinated when influenza is already circulating, you can get it before immunity has developed.
6. What are the contraindications to vaccination?
Egg hypersensitivity and a history of Guillain-Barré syndrome are the only absolute contraindications. Persons who have had sensitivity reactions when vaccinated previously should be excluded: some of these may have an egg hypersensitivity. The immune compromised are faced with the same mixture of circulating respiratory pathogens to which we are all exposed. They should not be given live virus vaccines: vaccines in common use don't contain live viruses.
Though the immune compromised may not mount as good an immune response as healthy persons, it is nevertheless desirable that their immune mechanism receives some protective stimulus. If they become infected with flu during the winter, they should receive anti-viral drugs whether vaccinated or not.
7. There are often delays in vaccine supply. How likely is this going to be this year and which month should we start vaccinating?
The manufacturing routine for influenza vaccines is complicated. The viruses are selected at the beginning of March and strains chosen that grow well on fertilised hens' eggs. Viruses grown in this way are harvested and destroyed in a way to leave the haemagglutinin and neuraminidase proteins intact.
This material is used to develop the vaccine which then has to be tested before releasing for general use. It is perhaps surprising that we do not have more frequent problems in the stage prior to marketing.
There is a delay this year for more than one manufacturer that may amount to four weeks. This will not matter very much unless we have a particularly early flu season.
8. Which month should we stop vaccinating?
Commence vaccination as soon as the vaccines are available to you. The more serious influenza epidemics have generally stated before Christmas and so it is important to vaccinate early.
There can be more than one virus strain circulating in winter and so there are sometimes benefits to be obtained even from
late vaccination. But policy should be directed towards vaccinating early in the winter.
9. How should antiviral therapy be used?
NICE has advised that the neuraminidase inhibitor anti-viral drugs should be prescribed for persons with clinical flu if they belong to the recognised risk categories and if they can commence treatment within 48 hours of illness onset.
These drugs are also recommended for prophylactic use in nursing homes for the elderly if flu breaks out in the home.
10. If an epidemic/pandemic occurs, who should be offered anti-viral agents and when?
The use of anti-viral drugs will be determined if and when a pandemic emerges. Policy will be determined by the Department of Health in the light of expert advice. The policy will depend on:
•The quantity of anti-viral drugs available
•The imminence of an effective vaccine becoming available
•Epidemiological data from surveillance in other countries showing which age groups are worst affected
•The rate of spread of infection within households and communities
•The effectiveness of anti-viral drugs against the pandemic virus.
Doug Fleming is director of the RCGP Birmingham research unit and a GP in Birmingham
• The vaccine against flu given routinely each winter contains material from three different inactivated virus strains, chosen because they have been circulating recently.
• The protection given by vaccination is limited to infection with these strains or viruses with very similar haemagglutinin and neuraminidase characteristics.
• The vaccine planned for use this winter does not include an avian virus strain.
• You cannot catch flu from vaccination. The vaccine in routine use does not contain live virus material.
• The only side-effect from vaccination that has been shown in clinical trials is local soreness at the injection site.
• It takes about two weeks to build up immunity after vaccination.
• Historically, the name influenza has been applied to an acute respiratory infection with fever and cough as the principal symptoms, but the word is
now reserved for use in connection
with illnesses caused by influenza viruses.
• There are several types of influenza virus and only some of them cause illness in humans.
• The illness caused by influenza virus is highly variable, ranging from trivial symptoms to fatal infection.
• Influenza viruses are constantly changing and immunity acquired either from natural infection or from vaccination is limited to the particular strain type.
• Influenza viruses circulate in most winters and sometimes there is more than one type. You can therefore have more than one influenza infection in one winter.
• A pandemic occurs when a totally new virus is found which spreads rapidly between humans and causes significant illness. The last pandemic in the UK occurred in 1969.
‘Patients need to be told they
cannot get flu from the vaccine'
What I will do now...
Dr Stott comments on the answers to his questions
I was particularly impressed by the fact that since the virus is inactivated it can be given to virtually anyone unless they have an allergy to eggs or a history of Guillain Barre syndrome. It is also logical that since it is inactivated, it cannot give anyone even a ‘mild dose' of flu – though persuading patients of this might prove more difficult. The immunocompromised are obviously an important group to reach, though as the answer suggests, they may not mount a complete immune response. Maybe we have neglected them a little in the past. Despite the risk of being inundated by people who think they are ‘carers', I can't wait to get started!
Peter Stott is a GP in Tadworth, Surrey, and sits on the National Osteoporosis Society's scientific committee