Herd Immunity and Epidemic Size in Networks with Vaccination Homophily

TL;DR

This paper investigates how vaccination homophily influences herd immunity thresholds and epidemic sizes, revealing that homophily can significantly raise the required vaccination coverage and affect epidemic dynamics.

Contribution

It provides a theoretical analysis of the impact of vaccination homophily on herd immunity thresholds and epidemic sizes, highlighting its critical role in epidemic modeling.

Findings

Homophily increases the herd immunity threshold.

Strong homophily can make herd immunity unachievable.

Epidemic size rises with homophily strength for perfect vaccines.

Abstract

We study how the herd immunity threshold and the expected epidemic size depend on homophily with respect to vaccine adoption. We find that the presence of homophily considerably increases the critical vaccine coverage needed for herd immunity and that strong homophily can push the threshold entirely out of reach. The epidemic size monotonically increases as a function of homophily strength for a perfect vaccine, while it is maximized at a nontrivial level of homophily when the vaccine efficacy is limited. Our results highlight the importance of vaccination homophily in epidemic modeling.