Blacksburg, VA—Pharmacists who recall years when influenza vaccine was in short supply probably also recall the dilemma it caused for them: Who should have top priority for being immunized?
A study published recently in the journal PLOS Computational Biology provides an answer. Virginia Tech–led researchers found that immunizing children and the elderly, after high-risk individuals, has the greatest overall benefit when there are limited vaccine resources.
To reach that conclusion, the study team created a “synthetic population that works, moves, and mixes with other humans similar to a real community. Because of extreme detail in the simulation, the researchers were able to evaluate an epidemic's indirect or social effects, such as how one person’s vaccination would lower their family and co-workers’ risk of infection.
Background information in the article notes that previous studies have focused only on homogeneous populations, private benefits of vaccination, or a single metric for measuring the financial and medical effectiveness of vaccine priorities.
The study simulated an influenza pandemic in Chicago using agent-based transmission dynamic modeling. The population was distributed among high-risk and non-high risk groups in subpopulations aged 0–19 years, 20–64 years, and 65 years and older. Different attack-rate scenarios for catastrophic (30.15%), strong (21.96%), and moderate (11.73%) influenza pandemics were compared with vaccine intervention scenarios at 40% coverage, 40% efficacy, and unit cost of $28.62.
The new model revealed that the overall financial impact of vaccination is much greater than scientists had previously assumed.
“Depending upon the severity of influenza, the ‘return on investment’ can increase from 3 to 7 times if we factor in how the immunity of vaccinated individuals indirectly benefits their contacts in the community by blocking the chain of transmission,” explained study coauthor Achla Marathe, PhD, a professor at the Biocomplexity Institute of Virginia Tech.
Researchers determined that the influenza infection rates among children were higher than among the adults and seniors in the catastrophic, strong, and moderate influenza pandemic scenarios “due to their larger social contact network and homophilous interactions in school.”
“Based on return on investment and higher attack rates among children, we recommend prioritizing children (0–19 years) and seniors (65+ years) after high-risk groups for influenza vaccination during times of limited vaccine supplies,” the authors write. “Based on risk of death, we recommend prioritizing seniors (65+ years) after high-risk groups for influenza vaccination during times of limited vaccine supplies.”
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