County-level MMR vaccination coverage in the U.S. before and after the COVID-19 pandemic: A modelling study

Authors: Ensheng Dong, Andreas Nearchou, Yamato Okura, Samee Saiyed, Lauren M. Gardner

Background: Childhood vaccination rates have been declining in the United States since the COVID-19 pandemic began. While COVID-19 exacerbated the decline in routine vaccination through disruption of healthcare services and the diversion of resources, factors including vaccine hesitancy, socioeconomic disparities and vaccine policy also contribute to changes in vaccination behavior. Understanding how these factors contribute to the spatially heterogeneous vaccination rates demands a high-resolution, data-driven analysis.

Methods: We collect county-level MMR vaccination rates for kindergarten children from 2017 - 2024, evaluate coverage patterns and trends before and after the COVID-19 pandemic, and implement multivariable weighted logistic regression models to identify factors associated with low and declining MMR vaccination rates in U.S. counties.

Findings: We reveal a nationwide decline in MMR rates following the COVID-19 pandemic, with declines observed in 415 out of 2,266 counties evaluated. We find state-level non-medical exemption (NME) policies to be strongly associated with low and declining MMR rates. We identify a positive association in vaccination rates across vaccine types. We find higher MMR rates are positively associated with Republican-aligned counties, while declines in MMR rates are positively associated with COVID-19 death rates.

Interpretation: The significant association between NMEs and low and declining MMR rates suggest these state level policies are harmful by increasing vaccine refusal. The positive associations among vaccine types suggest spillover effects in vaccine seeking behavior. The association between MMR rates and Republican-aligned counties contrast COVID-19 vaccination patterns, highlighting the complex nature of political polarization on vaccine-related behavior, while the association between MMR declines and COVID-19 death rate reveals an additional burden posed by the pandemic.

Funding: This work was supported by a grant from Bloomberg Philanthropies awarded to the Johns Hopkins Bloomberg Center for Government Excellence, City Analytics Initiative.