TY - JOUR
T1 - High vaccine effectiveness against severe COVID-19 outcomes and population preventable fraction during the Omicron era in Luxembourg
T2 - A nationwide retrospective risk factor analysis
AU - Bejko, Dritan
AU - Ernst, Corinna
AU - Vergison, Anne
AU - Stranges, Saverio
AU - Zeegers, Maurice P.
AU - Mossong, Joël
N1 - Funding Information:
The authors wish to thank the General Inspectorate of Social Security for providing data for analysis through the Luxembourg Microdata Platform on Labor and Social Protection. Additionally, they appreciate the efforts of the statistics/epidemiology team at the Directorate of Health in Luxembourg for their meticulous management of hospitalization data. During the preparation of this work the authors used artificial intelligence (AI), specifically OpenAI's ChatGPT in order to improve scientific writing in English. After using this tool, the author(s) reviewed and edited the content as needed and take full responsibility for the content of the publication.
Publisher Copyright:
© 2024 The Authors
PY - 2024/1/1
Y1 - 2024/1/1
N2 - Background: Luxembourg experienced major consecutive SARS-CoV-2 infection waves due to Omicron variants during 2022 while having achieved a high vaccination coverage in 2021. We investigated the risk factors associated to severe outcomes (i.e., hospitalisation, deaths) and estimated vaccine effectiveness (VE) as well as the role of immunity conferred by prior infections against severe outcomes in adults. Methods: We linked reported SARS-CoV-2 cases among residents aged = 20 years with vaccination data and SARS-CoV-2 related hospitalisations and deaths. Cases were followed-up until day 14 for COVID-19 related hospital admission and up to day 28 for mortality after a positive test. We analysed the association between the vaccination status and severe forms using proportional Cox regression, adjusting for previous infection, age, sex and nursing homes residency. VE was measured as 1-adjusted hazard ratio of vaccinated vs unvaccinated individuals. The population preventable fraction was computed using the adjusted hazard ratio and the proportion of cases within the vaccination category. Results: Between December 2021, and March 2023, we recorded 187 143 SARS-CoV-2 cases, 1 728 (0.93%) hospitalizations and 611 (0.33%) deaths. The risk of severe outcomes increased with age, was higher among men and nursing home residents. Compared to unvaccinated adults, VE against hospitalization was 38.8% (95%CI: 28.1%-47.8%) for a complete primary cycle of vaccination, 62.1% (95%CI: 57.0%-66.7%) for one booster, and 71.6% (95%CI: 66.7%-76.2%) for two booster doses. VE against death was respectively 49.5% (95%CI: 30.8%-63.3%), 69.0% (95%CI: 61.2%-75.3%) and 76.2% (95%CI: 68.4%-82.2%). Previous infection was not associated with lower risk of hospitalisation or mortality. The vaccination lowered mortality by 55.8 % (95%CI: 46.3%-62.8%) and reduced hospital admissions by 49.1% (95%CI: 43.4%-54.4%). Conclusions: Complete vaccination and booster but not previous infection were protective against hospitalization and death. The vaccination program in Luxembourg led to substantial reductions in SARS-CoV-2-related mortality and hospitalizations at the population level.
AB - Background: Luxembourg experienced major consecutive SARS-CoV-2 infection waves due to Omicron variants during 2022 while having achieved a high vaccination coverage in 2021. We investigated the risk factors associated to severe outcomes (i.e., hospitalisation, deaths) and estimated vaccine effectiveness (VE) as well as the role of immunity conferred by prior infections against severe outcomes in adults. Methods: We linked reported SARS-CoV-2 cases among residents aged = 20 years with vaccination data and SARS-CoV-2 related hospitalisations and deaths. Cases were followed-up until day 14 for COVID-19 related hospital admission and up to day 28 for mortality after a positive test. We analysed the association between the vaccination status and severe forms using proportional Cox regression, adjusting for previous infection, age, sex and nursing homes residency. VE was measured as 1-adjusted hazard ratio of vaccinated vs unvaccinated individuals. The population preventable fraction was computed using the adjusted hazard ratio and the proportion of cases within the vaccination category. Results: Between December 2021, and March 2023, we recorded 187 143 SARS-CoV-2 cases, 1 728 (0.93%) hospitalizations and 611 (0.33%) deaths. The risk of severe outcomes increased with age, was higher among men and nursing home residents. Compared to unvaccinated adults, VE against hospitalization was 38.8% (95%CI: 28.1%-47.8%) for a complete primary cycle of vaccination, 62.1% (95%CI: 57.0%-66.7%) for one booster, and 71.6% (95%CI: 66.7%-76.2%) for two booster doses. VE against death was respectively 49.5% (95%CI: 30.8%-63.3%), 69.0% (95%CI: 61.2%-75.3%) and 76.2% (95%CI: 68.4%-82.2%). Previous infection was not associated with lower risk of hospitalisation or mortality. The vaccination lowered mortality by 55.8 % (95%CI: 46.3%-62.8%) and reduced hospital admissions by 49.1% (95%CI: 43.4%-54.4%). Conclusions: Complete vaccination and booster but not previous infection were protective against hospitalization and death. The vaccination program in Luxembourg led to substantial reductions in SARS-CoV-2-related mortality and hospitalizations at the population level.
KW - COVID-19
KW - Hospital admission
KW - Mortality
KW - Natural immunity
KW - Retrospective cohort
KW - Vaccine effectiveness
U2 - 10.1016/j.vaccine.2024.05.059
DO - 10.1016/j.vaccine.2024.05.059
M3 - Article
SN - 0264-410X
VL - 42
JO - Vaccine
JF - Vaccine
IS - 22
M1 - 126011
ER -