Homologous and Heterologous Prime-Boost Vaccination: Impact on Clinical Severity of SARS-CoV-2 Omicron Infection among Hospitalized COVID-19 Patients in Belgium
Marjan Meurisse,
Lucy Catteau,
Joris A. F. van Loenhout,
Toon Braeye,
Laurane De Mot,
Ben Serrien,
Koen Blot,
Emilie Cauët,
Herman Van Oyen,
Lize Cuypers,
Belgian Collaborative Group on COVID-19 Hospital Surveillance,
COVID-19 Genomics Belgium Consortium,
Annie Robert,
Nina Van Goethem
Affiliations
Marjan Meurisse
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
Lucy Catteau
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
Joris A. F. van Loenhout
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
Toon Braeye
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
Laurane De Mot
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
Ben Serrien
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
Koen Blot
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
Emilie Cauët
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
Herman Van Oyen
Department of Public Health and Primary Care, Ghent University, 9000 Ghent, Belgium
Lize Cuypers
Department of Laboratory Medicine, National Reference Center for Respiratory Pathogens, University Hospitals Leuven, 3000 Leuven, Belgium
Belgian Collaborative Group on COVID-19 Hospital Surveillance
COVID-19 Genomics Belgium Consortium
Annie Robert
Department of Epidemiology and Biostatistics, Institut de Recherche Expérimentale et Clinique, Faculty of Public Health, Université Catholique de Louvain, 1200 Woluwe-Saint-Lambert, Belgium
Nina Van Goethem
Department of Epidemiology and public health, Sciensano, 1070 Brussels, Belgium
We investigated effectiveness of (1) mRNA booster vaccination versus primary vaccination only and (2) heterologous (viral vector–mRNA) versus homologous (mRNA–mRNA) prime-boost vaccination against severe outcomes of BA.1, BA.2, BA.4 or BA.5 Omicron infection (confirmed by whole genome sequencing) among hospitalized COVID-19 patients using observational data from national COVID-19 registries. In addition, it was investigated whether the difference between the heterologous and homologous prime-boost vaccination was homogenous across Omicron sub-lineages. Regression standardization (parametric g-formula) was used to estimate counterfactual risks for severe COVID-19 (combination of severity indicators), intensive care unit (ICU) admission, and in-hospital mortality under exposure to different vaccination schedules. The estimated risk for severe COVID-19 and in-hospital mortality was significantly lower with an mRNA booster vaccination as compared to only a primary vaccination schedule (RR = 0.59 [0.33; 0.85] and RR = 0.47 [0.15; 0.79], respectively). No significance difference was observed in the estimated risk for severe COVID-19, ICU admission and in-hospital mortality with a heterologous compared to a homologous prime-boost vaccination schedule, and this difference was not significantly modified by the Omicron sub-lineage. Our results support evidence that mRNA booster vaccination reduced the risk of severe COVID-19 disease during the Omicron-predominant period.
