@article{Kissling_E-2025_219209,
title = {Recommendations for estimating and reporting vaccine effectiveness by time since vaccination: a COVID-19 case study},
author = {Kissling, E. and Nunes, B. and Hooiveld, M. and Martínez-Baz, I. and Monge, S. and Robertson, C. and Knol, M. and Sève, N. and Mlinarić, I. and Domegan, L. and Machado, A. and Whitaker, H. and Lazar, M. and Meijer, A. and Enkirch, T. and Casado, I. and Pérez-Gimeno, G. and William, N. and Enouf, V. and Filipović, S. and McKenna, A. and Rodrigues, A. and de Lusignan, S. and Timnea, O. and Latorre-Margalef, N. and Castilla, J. and Pozo, F. and Hamilton, M. and Masse, S. and Ilić, M. and Basile, L. and O’Donnell, J. and Guiomar, R. and Riess, M. and Popescu, R. and Rose, A. and Andrews, N. and Bacci, S. and Celentano, L. and Valenciano, M. and Moren, A. and Beutels, P. and Hens, N. and Rose, A.},
month = {nov},
year = {2025},
abstract = {Estimating COVID-19 vaccine effectiveness (VE) by time since vaccination (TSV) is essential for understanding how protection may change over time and enables meaningful comparisons across studies. This is important for accurate comparisons of VE against different SARS-CoV-2 variants/sublineages, across age groups, during different periods post vaccination campaign, or by vaccine type/brand. We provide recommendations for case–control VE studies on estimating and reporting VE analyses by TSV, with the aim of improving quality of these estimates. Our recommendations cover study design and pre-analysis considerations, descriptive analyses, choice of categories of TSV, categorical and continuous modelling approaches, and best practices for reporting VE by TSV. Using a real-life case–control study, we apply these recommendations, and include accompanying statistical scripts in R and Stata. These recommendations will serve as a practical resource for researchers conducting VE analyses by TSV. We encourage ongoing refinement of them through input from other study groups.},
journal = {American Journal of Epidemiology},
publisher = {Oxford University Press},
url = {https://doi.org/10.1093/aje/kwaf254},
}
