Effectiveness of Post-Exposure Prophylaxis in Preventing Severe SARS-Cov2 Disease (PEP-VAX)

COVID-19 vaccination campaign in Italy primarily focused on preventing epidemic clusters between guests and workers in nursing homes.Despite the administration of the first vaccine dose, two epidemic clusters burst few days after vaccination: the short latency between vaccine inoculation and symptoms manifestation suggests that infection could be already occurred before the first vaccine dose.In this study we enrolled 149 patients from four different nursing homes that were comparable two by two about medical assistance features, age and clinical complexity of guests.Two of these facilities received the first vaccine dose shortly before the onset of the epidemic clusters, which resulted in a significantly reduced morbidity and mortality rate.The aim of the study is to define the principal risk factors associated to severe COVID-19 disease and to evaluate the impact of a potential post-exposure prophylaxis on SARS-CoV-2 infection mortality rate.