IntroductionThe I-MOVE-COVID-19 and VEBIS hospital networks have been measuring COVID-19 vaccine effectiveness (VE) in participating European countries since early 2021.AimWe aimed to measure VE against PCR-confirmed SARS-CoV-2 in patients ≥ 20 years hospitalised with severe acute respiratory infection (SARI) from December 2021 to July 2022 (Omicron-dominant period).MethodsIn both networks, 46 hospitals (13 countries) follow a similar test-negative case-control protocol. We defined complete primary series vaccination (PSV) and first booster dose vaccination as last dose of either vaccine received ≥ 14 days before symptom onset (stratifying first booster into received < 150 and ≥ 150 days after last PSV dose). We measured VE overall, by vaccine category/product, age group and time since first mRNA booster dose, adjusting by site as a fixed effect, and by swab date, age, sex, and presence/absence of at least one commonly collected chronic condition.ResultsWe included 2,779 cases and 2,362 controls. The VE of all vaccine products combined against hospitalisation for laboratory-confirmed SARS-CoV-2 was 43% (95% CI: 29-54) for complete PSV (with last dose received ≥ 150 days before onset), while it was 59% (95% CI: 51-66) after addition of one booster dose. The VE was 85% (95% CI: 78-89), 70% (95% CI: 61-77) and 36% (95% CI: 17-51) for those with onset 14-59 days, 60-119 days and 120-179 days after booster vaccination, respectively.ConclusionsOur results suggest that, during the Omicron period, observed VE against SARI hospitalisation improved with first mRNA booster dose, particularly for those having symptom onset < 120 days after first booster dose.

AP HP Hôpital Cochin Paris France

Cantacuzino National Military Medical Institute for Research Development Bucharest Romania

Carol Davila University of Medicine and Pharmacy Bucharest Romania

Centre for Infectious Disease Control National Institute for Public Health and the Environment Bilthoven the Netherlands

Centre Hospitalier de Luxembourg Luxembourg

Consortium for Biomedical Research in Epidemiology and Public Health Madrid Spain

Croatian Institute of Public Health Zagreb Croatia

Dirección General de Salud Pública y Ordenación Farmacéutica Junta de Andalucía Spain

Dr Victor Babes Clinical Hospital of Infectious and Tropical Diseases Bucharest Romania

Epiconcept Paris France

European Centre for Disease Prevention and Control Stockholm Sweden

Faculty of Medicine Lund University Lund Sweden

Faculty of Medicine Masaryk University Brno Czechia

Faculty of Medicine University of Paris City Paris France

Grigore T Popa University of Medicine and Pharmacy Iasi Romania

Health Service Executive Health Protection Surveillance Centre Dublin Ireland

IDCU within Health promotion and disease prevention Directorate G'mangia Malta

Inserm CIC Cochin Pasteur Paris France

Inserm US19 Villejuif Paris France

Instituto de Salud Pública de Navarra IdiSNA Pamplona Spain

Julius Center for Health Sciences and Primary Care University Medical Center Utrecht Utrecht the Netherlands

Lithuanian University of Health Sciences Kaunas Lithuania

Luxembourg Institute of Health Luxembourg

National Centre for Epidemiology Institute of Health Carlos 3 Madrid Spain

National Centre for Microbiology Institute of Health Carlos 3 Madrid Spain

National Institute of Health Dr Ricardo Jorge Lisbon Portugal

National Laboratory for Health Security Epidemiology and Surveillance Centre Semmelweis University Budapest Hungary

National Public Health Organisation Athens Greece

Robert Koch Institute Berlin Germany

Sciensano Brussels Belgium

St Parascheva Clinical Hospital of Infectious Diseases Iasi Romania

Teaching Public Health Institute of Split Dalmatia County Split Croatia

Universitair Ziekenhuis Brussel Brussels Belgium

University Hospital Brno Brno Czechia

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