Misclassification of yellow fever vaccination status revealed through hierarchical Bayesian modeling

Vaccination coverage estimates are crucial inputs to decisions about investments in vaccination, yet they can be prone to inaccuracies. At the individual level, inaccuracies can be described in terms of the sensitivity and specificity of vaccination status. We estimated these quantities using a hierarchical Bayesian analysis of data from a test-negative study design with reported yellow fever vaccination status as the exposure. Our analysis accounted for the possibility of misclassification of both the exposure and the test at the country level. Across all countries, our median estimates of the sensitivity and specificity of vaccination status were 0.69 (95% credible interval [CrI]: 0.21-0.98) and 0.70 (95% CrI: 0.21-0.98), respectively. Median estimates at the country level ranged from 0.06 (95% CrI: 0.04-0.09) to 0.96 (95% CrI: 0.94-0.98) for sensitivity, and from 0.15 (95% CrI: 0.09-0.23) to 0.98 (95% CrI: 0.90-1.00) for specificity. This suggests that there is substantial misclassification of yellow fever vaccination status in general and extensive variation in misclassification across countries. Taking into account misclassification in vaccination status, we made adjustments to reported vaccination coverage and showed that reported coverage may be significantly underestimated in 10 out of 20 countries and significantly overestimated in 5 out of 20. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported, in whole or in part, by the Bill & Melinda Gates Foundation, via the Vaccine Impact Modelling Consortium [Grant Number INV-009125]. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data are not available due to the fact that they were made available to the study authors by a third party through a data-sharing agreement with the data provider that does not allow data sharing by the authors.