To know how vaccines protect populations, we need to know how they work in individuals

Embargoed until: Publicly released: 2025-02-19 11:01

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Models of vaccine effectiveness in a population of people need to incorporate how they act in individuals, say US researchers. They modelled infectious disease spread under two types of vaccine coverage: 'all-or-nothing', where vaccination gives full protection for most, but no protection for some individuals, and 'leaky' protection, in which vaccination partly reduces everyone's chance of infection. When comparing predicted epidemic sizes, the 'all-or-nothing' model had an earlier peak with fewer infections. The researchers say information on vaccine 'failure modes' should be included when modelling vaccinations' impact on epidemics, and could help better prioritise vaccination for different groups, such as those more likely to transmit infection or at higher risk of serious illness.

Media release

From: The Royal Society

Vaccines are important for controlling infectious diseases, yet rarely offer perfect protection. Clinical trials determine vaccine efficacy at a population level, but mathematical models used to predict vaccination impacts require specifying how vaccines fail at the individual level, which is hard to measure. Does 90% efficacy imply full protection in 90% of those vaccinated and no protection in 10% (“all-or-nothing”), or that risk is reduced by 90% in all vaccinated individuals (“leaky”), or somewhere in between? Here we show that this modeling choice can significantly impact model predictions and affect decisions about optimal vaccine allocation.

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Journal/
conference: Journal of the Royal Society Interface

Research:Paper

Organisation/s: Johns Hopkins University - USA

Funder: Funding for this work was supported by the Centers for Disease Control and Prevention (75D30121F00005—A.L.H. and 6NU38FT000012 —A.L.H., A.N.) and the National Institutes of Health (DP5OD019851—A.L.H., A.N., T.A., D.A.L. and R01AI146129—M.Z.L.). The contents of this paper are solely the responsibility of the authors and do not necessarily represent the official views of the funding agencies.

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