Swedish Study: Omicron More Transmissible, Far Less Dangerous In Vaccinated Population—Hybrid Immunity Ignored

Swedish medical researchers sought to better understand the incidence of nosocomial SARS-CoV-2 infections and associated 30-day mortality among patients admitted to hospitals in the Stockholm region of that Scandinavian nation. Investigating this matter, the study team represented by corresponding author Nishi Dave, MSc,  a Ph.D. student, Department of Medicine, Solna, Division of Infectious Diseases, Karolinska Institutet, designed a retrospective, matched cohort study segmenting study period from March 1, 2020, until September 15, 2022, into a pre-vaccination period, early vaccination and pre-Omicron (period 1), and late vaccination and Omicron (period 2). From among 303,898 patients 18 years or older living in the Stockholm region, 538,951 hospital admissions across all hospitals were included in this analysis. Hospitalized admissions with nosocomial SARS-CoV-2 infections were matched to as many as 5 hospitalized admissions without nosocomial SARS-CoV-2 by age, sex, length of stay, admission time, and hospital unit. The authors report, &ldquo;Nosocomial SARS-CoV-2 infections were associated with higher 30-day mortality during the early phases of the pandemic and lower mortality during the Omicron variant wave and after the introduction of vaccinations.&rdquo; It is now widely known that hybrid immunity is the strongest protection highlighting the importance as well of pre-existing infection-based natural immunity. The Swedish authors avoid this topic. They report that the mitigation of excess mortality risk from nosocomial transmission should be a strong focus when population immunity is low through implementation of adequate infection prevention and control measures, whether that be vaccination or non-pharmaceutical interventions. Lots of the repurposed drugs that showed promise in terms of care intervention early on are avoided in these studies. 
Study authors were affiliated with multiple departments within the prestigious Karolinska Institutet, Karolinska University Hospital, Ume&aring; University as well as University Medical Centre Utrecht, Utrecht, the Netherlands.