Influenza: it's wise to immunize

Influenza is a logocontagious viral respiratory infection, which typically occurs as epidemics during the winter months in temperate zones. It is usually mild and uncomplicated, but may occasionally cause severe disease, particularly in vulnerable populations.

Seasonal influenza vaccination is the single most effective protective measure against the virus.Flickr: El Alvi

Since 2008, annual surveys of influenza vaccination policies, practices and coverage have been undertaken in 29 European Union (EU)/ European Economic Area (EEA) countries. In December 2009 the EU Council of Ministers agreed to take action to mitigate the impact of seasonal influenza by encouraging vaccination among older people, people with chronic conditions and healthcare workers. The aim? To increase vaccination coverage of older age groups to a target of 75% vaccination coverage by the 2014-15 winter season.

The results of the surveys indicate that most EU/EEA countries recommend influenza vaccination for the main target groups; however, only a few countries have achieved the target of 75% coverage among risk groups. In particular, vaccination coverage among health care workers who are at increased risk of exposure and who may be a source of virus transmission, remains low.

As discussed in a paper recently published in BMC Public Health by Emmanuelle Preaud and colleagues, despite the Council recommendation in 2009, vaccination coverage rates in Europe have not increased since then and there is evidence of declining trends across all EU member States.

In their work, the research team have generated a model to assess the public health benefits and economic importance of influenza vaccination in the 5 WHO recommended vaccination target groups (children 6 – 23 months of age; persons with underlying chronic health conditions; pregnant women, health care workers; and, the elderly, 65 years of age).

Using model estimations based on standard calculation methods, conservative assumptions, age-based and country-specific data, the authors estimated the number of eligible persons in different risk groups who would need to be vaccinated to achieve the 75% vaccination coverage target in 27 EU countries. They found that seasonal influenza vaccination in Europe currently averts between 1.6 to 2.1 million cases each year, and prevents between 25,200 and 37,200 deaths, with corresponding significant impact on hospitalizations, GP visits and costs avoided.

Flickr: Esparta PalmaIn an accompanying commentary by Giovanni Rezza, Section Editor for BMC Public Health, and co-author Bruno Christian Ciancio, it is argued that, although vaccination coverage figures in Europe are quite reliable for individuals older than 64 years, they are much less so for other target groups. As only few countries have comprehensive vaccination registries and few ad hoc studies are available to provide reliable figures, the estimation of the vaccine gap is likely to be imprecise.

Despite this, it is agreed that, even with suboptimal vaccine effectiveness, the benefits of increasing vaccination coverage would be enormous in terms of averted morbidity, mortality and cost.

With increasing vaccination coverage in EU/EEA countries being an immense challenge, Dr Rezza and Dr Ciancio propose that vaccination coverage should be monitored more effectively using vaccination registries or other administrative methods in combination with periodic population surveys. This, along with strengthening surveillance systems and research on immunological correlates of protection, is needed to provide accurate estimates of disease burden and to stimulate the development of more effective vaccines.

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