Studies demonstrating the waning of post-vaccination and post-infection immunity against covid-19 generally analyzed a limited range of vaccines or subsets of populations. Using Czech national health data from the beginning of the covid-19 pandemic till November 20, 2021 we estimated the risks of reinfection, breakthrough infection, hospitalization and death by a Cox regression adjusted for sex, age, vaccine type and vaccination status. Vaccine effectiveness against infection declined from 87% at 0-2 months after the second dose to 53% at 7-8 months for BNT162b2 vaccine, from 90% at 0-2 months to 65% at 7-8 months for mRNA-1273, and from 83% at 0-2 months to 55% at 5-6 months for the ChAdOx1-S. Effectiveness against hospitalization and deaths declined by about 15% and 10%, respectively, during the first 6-8 months. Boosters (third dose) returned the protection to the levels observed shortly after dose 2. In unvaccinated, previously infected individuals the protection against infection declined from 97% after 2 months to 72% at 18 months. Our results confirm the waning of vaccination-induced immunity against infection and a smaller decline in the protection against hospitalization and death. Boosting restores the original vaccine effectiveness. Post-infection immunity also decreases over time.

1st Faculty of Medicine Charles University Praha Czech Republic

Centre for Mathematical Biology Institute of Mathematics Faculty of Science University of South Bohemia České Budějovice Czech Republic

Centre for Modelling of Biological and Social Processes Praha Czech Republic

Czech Academy of Sciences Institute of Information Theory and Automation Praha Czech Republic

Department of Biochemistry Cell and Molecular Praha Czech Republic

Department of Ecology Czech Academy of Sciences Biology Centre Institute of Entomology České Budějovice Czech Republic

Department of Mathematics and Statistics Faculty of Science Masaryk University Brno Czech Republic

Department of Statistical Modelling Czech Academy of Sciences Institute of Computer Science Praha Czech Republic

Institute of Biostatistics and Analyses Faculty of Medicine Masaryk University Brno Czech Republic

Institute of Health Information and Statistics of the Czech Republic Praha Czech Republic

Siesta Labs Praha Czech Republic

PLoS One. 2023 Nov 28;18(11):e0295159. doi: 10.1371/journal.pone.0295159. PubMed

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