key: cord-0982791-ol9o0wua authors: Strålin, Kristoffer; Bruce, Daniel; Wahlström, Erik; Walther, Sten; Carnahan, Moa Rehn, AnnaSara; Andersson, Emmi; Bark, Anna M Bennet; Hanberger, Håkan title: Impact of the Alpha VOC on disease severity in SARS-CoV-2-positive adults in Sweden date: 2021-08-30 journal: J Infect DOI: 10.1016/j.jinf.2021.08.043 sha: d7327d5ec89e5594f01926a1f1163a414041f0c7 doc_id: 982791 cord_uid: ol9o0wua nan Alpha VOC and those infected with non-VOC, regarding length of stay in hospital, length of stay in the intensive care unit (ICU), and mortality. The discrepancy between these community-based and hospital-based studies regarding the impact of the Alpha VOC on disease severity motivated us to conduct a Swedish study on disease severity in the population and among hospitalised individuals. Our primary analysis was a comparison between two national cohorts from a period prior to VOC introduction and a period of Alpha VOC dominance, respectively. Our secondary analysis included individuals diagnosed with Alpha VOC or non-VOC, respectively. The study was conducted by the Public Health Agency of Sweden and the National Board of Health and Welfare. Three key considerations for studies on the association between specific SARS-CoV-2 lineages and disease severity have been pointed out ( [average 27 600/week]; median age 41 years, 49% females). Among whole genome sequenced SARS-CoV-2-positive cases in Sweden, no case of Alpha VOC was identified during weeks 45-51 (the first case was identified in week 52) (7), but was identified in 87-95% of cases during weeks 12-16 (8). Until week 16, the vaccination against Covid-19 in Sweden had mainly covered persons with high age, care dependency, and/or comorbidity. The secondary analysis was based on a nationwide typing project of individuals who were SARS-CoV-2 positive during weeks 5-12 (2021). Using targeted typing PCR, 12 321 individuals meeting the inclusion criteria were confirmed to be either Alpha VOC positive (n=8273; median age 42 years, 55% females) or VOC negative (n=4048; median age 41 years, 51% females). Nationwide register data on demographic factors, country of birth, care dependency, comorbidity, hospitalisation, ICU admission, mortality, discharge codes, SARS-CoV-2 positivity, and related variables were compiled, using the unique national personal identification number, as described previously (9) . Individuals who were admitted to hospital for any reason 5 days prior until 14 days after the first SARS-CoV-2 positive test were considered hospitalised due to COVID-19. Those who either received high-flow nasal oxygen (according to a specific national discharge code) or were admitted to an ICU during their hospital stay were considered to have severe illness due to COVID-19. The results of the two analyses are displayed in Table 1 . Compared to the non-VOC cohort, the Alpha VOC dominated cohort had significantly higher rates of hospitalisation, severe illness, and death overall, and a significantly higher rate of severe illness among hospitalised individuals. In the secondary analysis, Alpha VOC positive individuals had significantly higher rates of hospitalisation and severe illness than VOC negative individuals overall, but the numbers were too small to evaluate differences in severity rate among hospitalised individuals. In conclusion, in this Swedish population of SARS-CoV-2-positive adult individuals, without risk factors, infection with the Alpha VOC was associated with greater disease severity in the overall population which is in agreement with most other community based studies (3). However, among hospitalised individuals, we found a higher frequency of severe illness in the Alpha VOC dominated cohort than in the non-VOC cohort, indicating greater severity of Alpha VOC also in hospitalised individuals. This finding was in contrast to those of other Table 1 Outcome frequencies and odds ratios (OR) for national cohort and variant of concern (VOC) status comparisons, among SARS-CoV-2 positive individuals 20-69 years old without comorbidity and without care dependency in Sweden. Increased transmissibility and global spread of SARS-CoV-2 variants of concern as at European Centre for Disease Prevention and Control (ECDC). Variants of interest and concern in the EU/EEA (beta) SARS-CoV-2 variants and considerations of inferring causality on disease severity Mortality and critical unit admission associated with the SARS-CoV-2 lineage B.1.1.7 in England: an observational cohort study Genomic characteristics and clinical effect of the emergent SARS-CoV-2 B.1.1.7 lineage in London, UK: a wholegenome sequencing and hospital-based cohort study Statistik om SARS-CoV-2 virusvarianter av särskild betydelse Mortality trends among hospitalised COVID-19 patients in Sweden: A nationwide observational study The authors wish to thank Johanna Holm, Thomas Lindén, and Mona Heurgren at the National Board of Health and Welfare for valuable discussions regarding study design, and Shaman Muradrasoli and Mia Brytting at the Public Health Agency of Sweden for their invaluable work on the virological surveillance of SARS-CoV-2 in Sweden. All clinical microbiological laboratories contributing with diagnostics and PCR-typing of the samples are greatly acknowledged.