Vaccine effectiveness against infection and onwards transmission of COVID-19: Analysis of Belgian contact tracing data, January-June 2021
Toon Braeye, Laura Cornelissen, Lucy Catteau, Freek Haarhuis, Kristiaan Proesmans, Karin De Ridder, Achille Djiena, Romain Mahieu, Frances De Leeuw, Alex Dreuw, Naïma Hammami, Sophie Quoilin, Herman Van Oyen, Chloé Wyndham-Thomas, Dieter Van Cauteren
Abstract
In Belgium, high-risk contacts of an infected person were offered PCR-testing irrespective of their vaccination status. We estimated vaccine effectiveness (VE) against infection and onwards transmission, controlling for previous infections, household-exposure and temporal trends. We included 301,741 tests from 25 January to 24 June 2021. Full-schedule vaccination was associated with significant protection against infection. In addition, mRNA-vaccines reduced onward transmission: VE-estimates increased to >90% when index and contact were fully vaccinated. The small number of viral-vector vaccines included limited interpretability.