Influenza vaccination: revision of the indication

Influenza vaccination: who should be vaccinated and who should not?

Influenza is caused by the influenza virus. Because the virus is constantly changing, people do not build up life-long resistance, as frequently happens with other infectious diseases. This explains why there are annual epidemics. Healthy
individuals are usually well able to withstand an infection, but for people in the risk groups, influenza can lead to serious illness and even death (for example as a result of pneumonia, diabetes dysregulation or aggravation of lung and heart
disease).
There has consequently been a specific policy for a longer period of time whereby people who are at risk for developing complications in connection with influenza are offered influenza vaccination. In 1997, an infrastructure was established for this very purpose: the National Influenza Prevention Programme (NPG). Owing to the changes that influenza viruses undergo, vaccination needs to be repeated annually and the vaccine has to be continually modified.
A recurring question in this connection is which sections of the population should be offered influenza vaccination. New research data may, for example, reveal that vaccination of a particular group is insufficiently effective, or that other target groups who were not previously eligible for vaccination may actually be the ones who stand to derive major health benefits. The choice of target groups is therefore reviewed on a regular basis. With this in mind, the Minister of Health, Welfare and Sport requested the Health Council to consider which risk groups should be eligible for influenza vaccination in the years to come. The Minister also wished to know how it might be possible to maintain – or even further increase – the level of vaccination coverage within the target groups, which is already high.
So that it can advise the Minister, the Health Council has applied the seven vaccination criteria that were formulated in its advisory report The future of the National Immunisation Programme (RVP): Towards a programme for all age groups.These criteria were drawn up in order to make decisions on inclusion of vaccinations under the RVP. They can, however, equally well be applied when choosing target groups for the National Influenza Prevention Programme.

Majority of the current target groups to be retained

For the large majority of the current target groups, the beneficial effect of influenza vaccination remains undisputed. For this section of the population, vaccination serves to prevent significant damage to health, or at least to substantially reduce any damage that does occur. Furthermore, it is cost-effective to offer vaccination as part of a national programme. Thus the earlier recommendation that influenza vaccination should be offered to these groups still stands.
This applies to the following groups: people aged 65 years and over, patients with abnormalities or a dysfunction of the airways and lungs, patients with chronic cardiac dysfunction, patients with diabetes mellitus, patients with chronic renal insufficiency, patients who have recently undergone bone marrow transplantation, people with HIV infection, children aged between 6 months and 18 years who receive long-term salicylate therapy, people with mental retardation in residential institutions, people with reduced resistance to infection (e.g. because of cirrhosis,(functional) asplenia, autoimmune diseases, chemotherapy and immunosuppressive medication), and residents of nursing homes who do not fall into one of these categories.
The main topic of discussion was whether children with asthma should still be offered influenza vaccination. Earlier publications pointed to increased mortality as a result of influenza in this group and suggested that vaccination had a beneficial effect which could be measured by a reduction in respiratory infections and visits to the general practitioner (GP). However, recently published Dutch research has not corroborated these results. Nevertheless, the possibility that influenza vaccination may have a beneficial effect in this risk group cannot be dismissed at this moment in time. A decision to stop offering vaccination to this group can only be made once further research has shed more light on this issue.
One target group has, however, been dropped from the programme. Up until now, vaccination against influenza has been recommended in the Netherlands for patients with furunculosis and for members of their family. However, it is unclear from the scientific data whether furunculosis patients are at greater risk of complications after influenza. Nor do we know how effective influenza vaccination is in this group.

Four new target groups to be added

Healthy people aged 60 to 65 years

Up until now it has been recommended that people over 65 years of age should be vaccinated against influenza. A study performed especially for this advisory report has now revealed that episodes of influenza can also lead to more GP visits, hospital admissions and higher mortality rates in healthy younger people. This is especially evident in the 60-65 year age group. Therefore it is recommended that this age group should also be offered influenza vaccination in the future.

Healthcare personnel in institutions

Although in theory healthcare personnel who work in healthcare institutions are actually no more burdened by influenza than people in other occupations, they may transmit the disease to patients. This is particularly important for people whose daily work brings them into contact with patients who are at high risk of complications from influenza. Vaccination reduces the risk of these complications. Healthcare personnel have a special responsibility in this respect.
Consequently, we recommend that healthcare personnel in hospitals, care homes and nursing homes should in the future be included among the target groups for vaccination.

Other healthcare personnel

Other healthcare personnel also regularly have intensive contact with patients at high risk of complications from influenza (home care workers and general practitioners, for example) and they too bear a special responsibility. In practice, it is actually difficult to draw the line between those professionals who are eligible for vaccination and those who are not. Consequently, a general recommendation has been made that healthcare personnel who in daily practise come into direct contact with patients should be vaccinated against influenza.

Family members of very high-risk individuals

Family members can be a source of infection for people who are at high risk when developing influenza. There are, however, no data available at present that prompt the Committee to recommend the vaccination of family members of people from all risk groups. The Committee nevertheless considers it prudent to recommend vaccination for family members of patients who are at particularly high risk. Examples are: patients with serious abnormalities of or a dysfunction of the airways and lungs, patients with severe liver or kidney failure, and patients whose immune system is compromised (e.g. as a result of HIV infection, chemotherapy or treatment with other drugs that suppress the immune system).

Other possible target groups not (yet) included

In other countries, influenza vaccination is offered to pregnant women. The scientific literature does not indicate, however, that healthy pregnant women are at higher risk when developing influenza. Moreover, they are rarely admitted to hospital during the influenza season, and mortality from influenza does not occur in this group. Thus there is no reason to add healthy pregnant women to the target groups for influenza vaccination.
Another target group for whom influenza vaccination has been considered are children. Research has been conducted especially for this advisory report into morbidity and mortality in children in the Netherlands as a result of influenza. Although the results do not show any additional mortality, they do reveal an extra disease burden in the form of more hospital admissions and GP visits.
The increased morbidity mainly applies to children aged between 0 and 6 months. However, influenza vaccines have not been registered for and tested in children from this age group and this group has consequently been ruled out. Vaccination of pregnant women could well be an alternative means of protecting newborn babies. There is, however, no scientific evidence that maternal vaccination is an effective means of achieving this goal and this is therefore not recommended.
Influenza also results in higher morbidity in children aged between 6 months and 2 years. However, the efficacy of the influenza vaccine has not been demonstrated in this age group. Although vaccination is effective in healthy children over 2 years of age, influenza does not cause additional serious morbidity or mortality in this group and hence there is no reason at present to include them among the target groups for influenza vaccination.
A further possible target group consists of people who have intensive contact with the general public through their work (lecturers, for example). Based on the available scientific literature, however, there is no reason to assume that these individuals would be at increased risk of influenza, complications or mortality in the event that they should fall ill. Nor are they more likely to transmit influenza to people for whom this would pose a serious threat. There is consequently no reason to offer vaccination to people in these occupations.
It has also been considered whether people with addictions to alcohol and drugs ought to be eligible for influenza vaccination. The Committee has found no evidence to suggest that these individuals might have low immunity and it therefore has no reason to assume that these groups are at increased risk of developing complications or even dying as a result of influenza. The committee therefore does not recommend to add them to the target groups for influenza vaccination either. They may, however, be eligible for vaccination for other reasons (e.g. because of cirrhosis or HIV infection). Healthcare providers need to be alert, since this group is often less familiar with regular care.
It has also been considered whether occupational groups who have intensive contact with poultry – such as poultry farmers and veterinarians – would benefit from yearly influenza vaccination. However, in the absence of an avian influenza epidemic, there is no reason to vaccinate them. If avian influenza were to break out, there would be a risk that genetic material might be exchanged between different strains of the virus, giving rise to the possibility that a new virus strain might emerge which is highly infectious for humans. Such a new strain might then lead to a pandemic (an epidemic on a global scale). In case of an outbreak of avian influenza, there may therefore be grounds for vaccinating professional groups who have intensive contact with poultry. This is a decision that the Minister of Health, Welfare and Sport would have to make at the time.

Boosting effectiveness through proper education

Many Dutch people who are eligible for an influenza vaccination do actually receive one in practice. Vaccination coverage is high. Nevertheless, not everyone has been reached as yet. For example, some people are unaware that they belong to a target group. Proper, well-targeted education can help to rectify this situation. Information about the risks of influenza and the mild side effects of vaccination may help to further boost vaccination coverage. Furthermore, the role of GPs is crucial in ensuring acceptance of vaccination. Their central role must therefore be maintained. Vaccination of healthcare personnel is best performed in the workplace, and this may possibly be a task for the occupational health services.

Further research

In assessing the current level of knowledge, the Committee has identified a number of gaps. It recommends that research be conducted in order to reduce these gaps. More specifically, focussed research is needed into the effectiveness of influenza vaccination in children aged between 6 months and 2 years and the effectiveness of influenza vaccination in children with asthma. Furthermore, general research is recommended into the possible indirect effects of influenza vaccination in healthy children (as a result of reduced transmission), research into the long-term effects that annual influenza vaccination at an early age may have on the clinical course of influenza later in life, and continuation and intensification of research aimed at improving the effectiveness of influenza vaccines.