The study, carried out by researchers at the London School of Hygiene & Tropical Medicine and Public Health England, led to the UK government changing its vaccine policy to extend flu vaccination to children. The researchers found that the most cost-effective option is extending the vaccination programme covering high risk and elderly individuals to children aged 5-16 years.
Most high income countries recommend that influenza vaccination should be targeted at individuals at highest risk of complications following infection, such as those with chronic heart or lung disease, metabolic or renal disease or immunodeficiencies, and the elderly.
In 2012, the World Health Organization (WHO) also recommended vaccination of children aged six months to 59 months, and there has been a recent recommendation to vaccinate all children in the US by the Advisory Committee on Immunization Practices, based on high hospitalisation rates in the younger age groups.
However, these recommendations tend to consider only the direct benefits of immunization for those receiving the vaccine. Targeting groups such as school aged children, who play a key role in the spread of influenza, could be a more efficient use of limited resources than targeting groups at highest risk of disease.
The researchers looked at the cost-effectiveness of extending the UK’s seasonal influenza immunization programme, which targeted high risk and elderly individuals over 65, to various low-risk groups of different ages, from young children to 50-64 year olds.
They used a mathematical model based on 14 years of surveillance data, gathered from 1995 to 2009, to simulate influenza transmission in a population of England and Wales representing an average total of 52.6 million people.
The team tested alternative vaccination scenarios, evaluating various outcomes including the number of infections, clinical cases, general practitioner consultations, hospitalisations, and deaths. They took into consideration vaccination programme costs, and a measure known as quality-adjusted life-years (QALY), which is used to assess the value for money of a medical intervention by taking into account both the quantity and quality of life generated.
Study author John Edmunds, Professor of Infectious Disease Modelling at the London School of Hygiene & Tropical Medicine, said: “Our findings are important because they show that vaccinating children against influenza may well be highly cost-effective. This is because vaccinating children not only helps protect them against flu, but also helps prevent spread to others in the community.”
The researchers found that the most cost-effective option was extension to 5-16 year old children. Universal vaccination (extension to all low risk individuals over two years) would achieve the highest net benefit.
The findings also showed that the extension of the UK programme in 2000 to include individuals over the age of 65 years, similar to current WHO recommendations, may not have made optimal use of resources. Although the extension was cost effective, an alternative extension to children would have yielded a substantially higher net benefit.
Study lead author Marc Baguelin, mathematical modeller and health economist at the London School of Hygiene & Tropical Medicine and Public Health England, said: “Our previous research has shown that children are the main transmitters of the different flu strains circulating. In this study we’ve now used mathematical models to assess the impact of different vaccination strategies in order to come up with the most cost-effective solution to inform government policy.”
As a result of the research, the Joint Committee on Vaccination and Immunisation recommended influenza vaccination for all children aged two to 17. This programme started in 2013-14, initially with pre-school children. This flu season, vaccinations will be delivered nationally in primary schools to children in school years one and two for the first time.
The authors note that influenza viruses are constantly evolving and that childhood vaccination, while retrospectively the best option, may not be optimal for future seasons if the influenza epidemiology changes substantially. Their model also does not consider the impact of repeated vaccinations and its wider effects on immunity in the population.
Marc Baguelin, Anton Camacho, Stefan Flasche and W. John Edmunds, Extending the elderly- and risk-group programme of vaccination against seasonal influenza in England and Wales: a cost-effectiveness study, BMC Medicine. DOI: 10.1186/s12916-015-0452-y
The Centre for the Mathematical Modelling of Infectious Diseases
Image: woman sneezing. Credit: SXC/evah
London School of Hygiene & Tropical Medicine