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Influenza is a common infectious disease affecting 5%-10% of adults and 20%-30% of children. There are an estimated 3 to 5 million cases of severe influenza-related illness worldwide each year, and 250 000 to 500 000 deaths (WHO, 2014). Influenza can also have a major impact on health care systems. In the United States, it is estimated that each year, more than 200 000 people are hospitalised for respiratory and heart condition illnesses associated with seasonal influenza virus infections (Thompson et al., 2004). At certain times of the year, influenza can place health systems under significant stress. For example, in Ontario, Canada, the average annual rate of emergency department visits attributable to seasonal influenza is 500 per 100 000 population. This rate increased to an estimated 1 000 per 100 000 population during the H1N1 pandemic in 2009 (Schanzer et al., 2013).
In 2003, countries participating in the World Health Assembly committed to the goal of attaining vaccination coverage against influenza of at least 50% of the elderly population by 2006 and 75% by 2010.Figure 8.37 shows that in 2013, the OECD average influenza vaccination rate for people aged 65 and over was 48%. Vaccination rates are as low as 1.1% in Estonia, where influenza vaccination is recommended but not free. Only four countries have attained the 75% target: Mexico, Korea, Chile and the United Kingdom. Australia came close to meeting the target.
Figure 8.38 indicates that between 2003 and 2013, the vaccination rate against influenza among the elderly population has remained stable on average among the group of OECD countries that have trend data over this period, but with no uniform trend across countries. In some countries, such as New Zealand, Israel, Germany, Denmark, the Czech Republic and the United Kingdom, the percentage of the population aged 65 and over vaccinated against influenza has increased, while it has come down in other countries such as the Netherlands, Spain, France, the Slovak Republic and Slovenia.
In June 2009, the WHO declared an influenza pandemic. The H1N1 influenza virus (also referred to as “swine flu” ) infected an estimated 11% to 18% of the global population (Kelly et al., 2011). Mexico was at the centre of the pandemic, being among the first countries where swine flu was detected and also where mortality rates were reportedly higher than those in many other countries. The high rate of seasonal vaccinations that are still being observed in Mexico may come as a result of the H1N1 experiences in that country. In other countries, however, the take-up rate of H1N1 vaccine was lower than expected, despite the vaccine being included in most 2009-10 vaccination programmes. In part, this may be due to the easing of concerns about the threat of H1N1 amongst the general population by the time the vaccine became available. Studies have shown that the most important determinant for individuals to take-up H1N1 vaccine was previous exposure to seasonal flu vaccine, leading some researchers to argue that higher vaccination rates for seasonal flu may help take-up during potential future pandemics (Nguyen et al., 2011).
Definition and comparability
Influenza vaccination rate refers to the number of people aged 65 and older who have received an annual influenza vaccination, divided by the total number of people over 65 years of age. In some countries, the data are for people over 60 years of age. The main limitation in terms of data comparability arises from the use of different data sources, whether survey or programme, which are susceptible to different types of errors and biases. For example, data from population surveys may reflect some variation due to recall errors and irregularity of administration.
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References
Kelly, H. et al. (2011), “The Age-specific Cumulative Incidence of Infection with Pandemic Influenza H1N1 2009 Was Similar in Various Countries Prior to Vaccination” , PLoS One, Vol. 6, No. 8:e21828.
Nguyen, T. et al. (2011), “Acceptance of A Pandemic Influenza Vaccine: A Systematic Review of Surveys of the General Public” , Infection and Drug Resistance, Vol. 4, pp. 197-207.
Schanzer, D.L., B. Schwartz and M.J. Mello (2013), “Impact of Seasonal and Pandemic Influenza on Emergency Department Visits, 2003-2010, Ontario, Canada” , Academic Emergency Medicine, Vol. 20, No. 4, pp. 388-397.
[autonumber to be developed]Thompson, W.W. et al. (2004), “Influenza-Associated Hospitalizations in the United States” , Journal of American Medical Association, Vol. 292, No. 11, pp. 1333-1340.
WHO (2014), “Influenza (Seasonal)” , Fact Sheet No. 211, available at:www.who.int/mediacentre/factsheets/fs211/en/ (accessed 23/06/2015).
Note: Information on data for Israel: http://dx.doi.org/10.1787/888933280737
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