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Targeting younger populations may decrease annual influenza transmission cycle
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Targeting school-aged children for receipt of the seasonal influenza vaccine could greatly reduce disease morbidity and mortality within the entire population, according to recent study findings published in Vaccine.
“In most cases, the available flu vaccine could be used more effectively and save more lives by increasing the number of vaccinated children and young adults,” study researcher Jan Medlock, PhD, of the department of biomedical sciences at Oregon State University’s College of Veterinary Medicine, said in a press release. “That approach could really limit the cycle of transmission, preventing a great deal of illness while also reducing the number of deaths among high-risk groups.”
The study included participants of all ages, but researchers focused on school-aged children (5 to 17 years) and young adults (18 to 44 years), and measured infections, hospitalizations, deaths, years of life lost and contingent valuation.
Researchers found an attack rate of 32% in the absence of vaccination. Annual vaccination coverage in the United States is 34%, at nearly 100 million doses per year.
“We showed that when more than 60 million doses of vaccine were distributed, optimization over uncertainty robustly yielded prioritization of vaccination to schoolchildren and young adults for all five measures considered,” researchers wrote.
When vaccine availability decreased, the priority shifted away from young adults to school-aged children. Researchers also found that if focus of vaccination shifted to include more children, young adults and those at high risk, a 25% to 200% reduction in deaths from influenza or its complications could be achieved.
“A simple program we could consider in our K to 12 schools would be to have the school nurse, or other local professional, give every child an annual flu shot, with the parents being informed about it in advance and having the option to decline,” Medlock said. “Vaccinating children could prevent a great deal of illness and save many lives at all ages, not just the children. More aggressive educational campaigns to reach young adults would also be helpful.”
Disclosure: The study was supported by the National Institute of General Medical Sciences.
Perspective
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Andrew T. Pavia, MD, FAAP, FIDSA
A number of mathematical modeling studies have concluded that, in general, vaccinating a large proportion of children against influenza is the best way to minimize the impact of influenza in all age groups. The authors of this study set about to construct a model in which you could include many of the uncertainties surrounding any given influenza season, including how easily it is spread (the reproductive rate R0, or ‘R nought’), how effective the vaccine is in that season, and how much vaccine is available.
They again concluded that, in general, vaccinating a large proportion of children and young adults provides the greatest protection for the population at large, as well as for the children and young adults. However, they found that if the amount of available vaccine is low, it becomes better to concentrate on vaccinating those at high risk of complications. The best strategy was also influenced by how effectively the virus transmitted. When each sick person infected many new patients (as might occur with a novel strain with a high R nought), then more lives might be saved by focusing on high-risk persons.
The authors also commented on the difficulty of getting rates of high vaccine coverage among children and young adults. The effectiveness of the targeted strategy requires better methods to get vaccine into those age groups.
The current US recommendations recommend influenza for all people, so this will not change clinical practice. However, it can influence public health strategies that aim to improve vaccination rates and may provide insights into how best to deal with vaccine shortages.
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