Is age-based vaccination really the best strategy against epidemics?

Faced with an epidemic like SARS-CoV-2, the rapid spread and high death toll made vaccine development essential. However, producing enough doses for the entire population takes time and is expensive. It then becomes crucial to determine who to vaccinate first to best limit the consequences. Many countries have chosen to prioritize people based on age, a simple approach whose effectiveness remains limited according to a recent scientific analysis.

Researchers compared this method to more than sixty other vaccination strategies, some well-known, others innovative. Their simulations show that age-based vaccination does effectively reduce the number of deaths, especially when vaccine supplies are very low. However, it proves less effective at stopping the spread of the virus or eradicating the disease. For example, nearly 90% of the population would need to be vaccinated to eliminate the virus using this approach—a rate much higher than that required with other methods.

Among the most effective alternatives is the strategy based on PageRank, a tool that identifies the most central individuals in the social contact network. This method reduces the number of deaths by more than 60% and total hospitalization duration by 66%. Additionally, it requires vaccinating less than 40% of the population to block transmission. PageRank, originally used to rank web pages, proves particularly suitable for identifying individuals whose vaccination protects the greatest number of people.

The explanation is simple: older people, although more vulnerable, generally have fewer social contacts than young adults. Vaccinating them as a priority protects mainly themselves but does not sufficiently limit the circulation of the virus in the population. Conversely, targeting the most connected individuals or those with the most frequent contacts allows transmission chains to be broken more effectively.

Researchers also tested so-called “altruistic” strategies, which aim to protect the most vulnerable people in everyone’s circle rather than focusing on self-protection. These approaches often prove more effective, especially in networks where interactions are unequal.

These findings are not limited to COVID-19. With the increasing risk of epidemics due to climate change and ecosystem destruction, these discoveries could guide public health policies in future crises. They highlight the importance of building realistic contact networks to refine strategies, using, for example, mobility data or surveys on social behaviors.

The study finally reminds us that the primary objective—whether to reduce deaths in the short term or eradicate the disease—strongly influences the choice of strategy. While age-based vaccination saves lives in the moment, it is not enough to prevent a long-term resurgence of the virus. For future epidemics, a more targeted and dynamic approach, based on social network analysis, could prove much more effective.

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About This Study

DOI: https://doi.org/10.1007/s41060-026-01053-5

Title: A new take on optimal vaccine prioritization: when age-based strategy is efficient?

Journal: International Journal of Data Science and Analytics

Publisher: Springer Science and Business Media LLC

Authors: Miguel Gonçalves; Pablo Ignacio Fierens; Leandro Chaves Rêgo