<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Marjan Meurisse</style></author><author><style face="normal" font="default" size="100%">Lucy Catteau</style></author><author><style face="normal" font="default" size="100%">Joris Van Loenhout</style></author><author><style face="normal" font="default" size="100%">Toon Braeye</style></author><author><style face="normal" font="default" size="100%">Laurane De Mot</style></author><author><style face="normal" font="default" size="100%">Ben Serrien</style></author><author><style face="normal" font="default" size="100%">Koen Blot</style></author><author><style face="normal" font="default" size="100%">Emilie Cauët</style></author><author><style face="normal" font="default" size="100%">Herman Van Oyen</style></author><author><style face="normal" font="default" size="100%">Lize Cuypers</style></author><author><style face="normal" font="default" size="100%">Annie Robert</style></author><author><style face="normal" font="default" size="100%">Nina Van Goethem</style></author></authors><translated-authors><author><style face="normal" font="default" size="100%">Belgian Collaborative Group on COVID-19 Hospital Surveillance</style></author><author><style face="normal" font="default" size="100%">COVID-19 Genomics Belgium</style></author></translated-authors></contributors><titles><title><style face="normal" font="default" size="100%">Homologous and Heterologous Prime-Boost Vaccination: Impact on Clinical Severity of SARS-CoV-2 Omicron Infection among Hospitalized COVID-19 Patients in Belgium</style></title><secondary-title><style face="normal" font="default" size="100%">Vaccines</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2023</style></year><pub-dates><date><style  face="normal" font="default" size="100%">Feb-07-2023</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">11</style></volume><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;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.&lt;/p&gt;
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