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Background Previous infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) provides strong protection against future infection. There is limited evidence on whether such protection extends to the Omicron variant. Methods This retrospective cohort study included 635 341 patients tested for SARS-CoV-2 via polymerase chain reaction from 9 March 2020 to 1 March 2022. Patients were analyzed according to the wave in which they were initially infected. The primary outcome was reinfection during the Omicron period (20 December 2021–1 March 2022). We used a multivariable model to assess the effects of prior infection and vaccination on hospitalization. Results Among the patients tested during the Omicron wave, 30.6% tested positive. Protection of prior infection against reinfection with Omicron ranged from 18.0% (95% confidence interval [CI], 13.0–22.7) for patients infected in wave 1 to 69.2% (95% CI, 63.4–74.1) for those infected in the Delta wave. In adjusted models, previous infection reduced hospitalization by 28.5% (95% CI, 19.1–36.7), whereas full vaccination plus a booster reduced it by 59.2% (95% CI, 54.8–63.1). Conclusions Previous infection offered less protection against Omicron than was observed in past waves. Immunity against future waves will likely depend on the degree of similarity between variants.

Background Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been shown to be highly protective against reinfection and symptomatic disease. However, effectiveness against the Delta variant and duration of natural immunity remain unknown. Methods This retrospective cohort study included 325 157 patients tested for SARS-CoV-2 via polymerase chain reaction (PCR) from 9 March 2020 to 31 December 2020 (Delta variant analysis) and 152 656 patients tested from 9 March 2020 to 30 August 2020 (long-term effectiveness analysis) with subsequent testing through 9 September 2021. The primary outcome was reinfection, defined as a positive PCR test >90 days after the initial positive test. Results Among 325 157 patients tested before 31 December 2020, 50 327 (15.5%) tested positive. After 1 July 2021 (Delta dominant period), 40 (0.08%) initially positive and 1494 (0.5%) initially negative patients tested positive. Protection of prior infection against reinfection with Delta was 85.4% (95% confidence interval [CI], 80.0–89.3). For the long-term effectiveness analysis, among 152 656 patients tested before 30 August 2020, 11 186 (7.3%) tested positive. After at least 90 days, 81 (0.7%) initially positive and 7167 (5.1%) initially negative patients tested positive. Overall protection of previous infection was 85.7% (95% CI, 82.2–88.5) and lasted up to 13 months. Patients aged >65 years had slightly lower protection. Conclusions SARS-CoV-2 infection is highly protective against reinfection with Delta. Immunity from prior infection lasts at least 13 months. Countries facing vaccine shortages should consider delaying vaccinations for previously infected patients to increase access.

Background The 2019 American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) guidelines argue against routine pneumococcal urinary antigen testing (pUAT), except in patients with severe community-acquired pneumonia (CAP). Recent studies, however, have suggested that these recommendations identify a low-risk population, resulting in missed opportunities for antimicrobial stewardship. The optimal patient population for pUAT thus remains unknown. Our objective was to summarize predictors of pUAT positivity among patients hospitalized with CAP as determined by previous observational studies. Methods We systematically searched MEDLINE, Embase, Web of Science, and Scopus for articles related to urinary antigen tests and community-acquired pneumonia. Studies published until August 26, 2021, were included if risk factors for pUAT positivity in adult patients with CAP were evaluated with multivariable analyses. No language filters or limits were applied in order to capture all potentially relevant material. Two investigators independently screened studies, extracted, and compiled data. Results Of the 1,144 studies that were screened, 9 met the inclusion criteria, representing 8,536 patients who underwent pUAT. The most frequent independent risk factors associated with a positive pUAT were intensive care unit (ICU) admission (OR 1.77, 95% CI 1.27 – 2.48, I2 = 21%) (Figure 1) and female sex (OR 1.53, 95% CI 1.19 – 1.97, I2 = 36%) (Figure 2). Laboratory parameters such as C-reactive protein (OR 0.26, 95% CI 0.02 – 4.49, I2 = 93%) and BUN (OR 1.36, 95% CI 0.84 – 2.19, I2 = 93%) were not significantly associated with pUAT positivity. Many variables were inconsistently reported and thus could not be combined for analysis, including age > 65, current smoking, history of emphysema, hyponatremia, certain markers of severity, and antibiotic history. Figure 1:Forest plot of the association between ICU admission and positive pneumococcal UAT. The vertical line corresponds to the no difference point between the two groups. Squares, the size of which indicates the proportion of information given by each study, correspond to ORs. Horizontal lines represent the 95% CIs. The diamond indicates the pooled odds ratios. df = degrees of freedom; IV = inverse variance Figure 2:Forest plot of the association between female sex and positive pneumococcal UAT. The vertical line corresponds to the no difference point between the two groups. Squares, the size of which indicates the proportion of information given by each study, correspond to ORs. Horizontal lines represent the 95% CIs. The diamond indicates the pooled odds ratios. df = degrees of freedom; IV = inverse variance Conclusion Consistent with current guidelines, ICU admission, an indication of severe CAP, appears to be an important predictor of pUAT positivity. Additionally, however, female sex was significantly associated with pUAT positivity. Recognition of these risk factors can assist in identifying patient populations most likely to benefit from pUAT and may be considered in future CAP guidelines. Disclosures Abhishek Deshpande, MD, PhD, Clorox: Grant/Research Support|Merck: Advisor/Consultant|Seres Therapeutics: Grant/Research Support.

Background Severe acute respiratory syndrome coronavirus 2 immunity has declined with subsequent waves and accrual of viral mutations. In vitro studies raise concern for immune escape by BA.4/BA.5, and a study in Qatar showed moderate protection, but these findings have yet to be reproduced. Methods This retrospective cohort study included individuals tested for coronavirus disease 2019 by polymerase chain reaction during Delta or BA.1/BA.2 and retested during BA.4/BA.5. The preventable fraction (PF) was calculated as ratio of the infection to the hospitalization rate for initially positive patients divided by the ratio for initially negative patients, stratified by age and adjusted for age, sex, comorbid conditions, and vaccination using logistic regression. Results A total of 20 987 patients met inclusion criteria. Prior Delta infection provided no protection against BA.4/BA.5 infection (adjusted PF, 11.9% [95% confidence interval, .8%–21.8%]); P = .04) and minimal protection against hospitalization (10.7% [4.9%–21.7%]; P = .003). In adjusted models, prior BA.1/BA.2 infection provided 45.9% (95% confidence interval, 36.2%–54.1%; P < .001) protection against BA.4/BA.5 reinfection and 18.8% (10.3%–28.3%; (P < .001) protection against hospitalization. Up-to-date vaccination provided modest protection against reinfection with BA.4/BA.5 and hospitalization. Conclusions Prior infection with BA.1/BA.2 and up-to-date vaccination provided modest protection against infection with BA.4/BA.5 and hospitalization, while prior Delta infection provided minimal protection against hospitalization and none against infection.

Previous infection with SARS-CoV-2 provides strong protection against future infection. There is limited evidence on whether such protection extends to the Omicron variant.This retrospective cohort study included 635,341 patients tested for SARS-CoV-2 via polymerase chain reaction (PCR) from 09 March 2020 to 01 March 2022. Patients were analyzed according to the wave in which they were initially infected. The primary outcome was reinfection during the Omicron period (20 December 2021, to 01 March 2022). We used a multivariable model to assess the effects of prior infection and vaccination on hospitalization.Among the patients tested during the Omicron wave, 30.6% tested positive. Protection of prior infection against reinfection with Omicron ranged from 18.0% (95% confidence interval [CI], 13.0-22.7) for patients infected in wave 1 to 69.2% (95% CI, 63.4-74.1) for those infected in the Delta wave. In adjusted models, previous infection reduced hospitalization by 28.5% (95% CI, 19.1-36.7), while full vaccination plus a booster reduced it by 59.2% (95% CI, 54.8-63.1).

Pneumonia is a leading cause of hospitalization and death due to infection worldwide.

Background Venous thromboembolism (VTE) prophylaxis is recommended for hospitalized medical patients at high risk for VTE. Multiple risk assessment models exist, but few have been compared in large datasets. Methods We constructed a derivation cohort using 6 years of data from 12 hospitals to identify risk factors associated with developing VTE within 14 days of admission. VTE was identified using a complex algorithm combining administrative codes and clinical data. We developed a multivariable prediction model and applied it to three validation cohorts: a temporal cohort, including two additional years, a cross-validation, in which we refit the model excluding one hospital each time, applying the refitted model to the holdout hospital, and an external cohort. Performance was evaluated using the C-statistic. Results The derivation cohort included 155,026 patients with a 14-day VTE rate of 0.68%. The final multivariable model contained 13 patient risk factors. The model had an optimism corrected C-statistic of 0.79 and good calibration. The temporal validation cohort included 53,210 patients, with a VTE rate of 0.64%; the external cohort had 23,413 patients and a rate of 0.49%. Based on the C-statistic, the Cleveland Clinic Model (CCM) outperformed both the Padua (0.76 vs. 0.72, p = 0.002) and IMPROVE (0.68, p Conclusion A new VTE risk assessment model outperformed recommended models.

This study investigates K-pop and K-pop fandom as an ongoing social movement. With popular South Korean group BTS as a case study, I examine how their fans join together and use collective action to create social change. My research answered three primary questions: (1) “How have K-pop fans been involved in societal causes prior to their recent surge in activism in 2020?,” (2) “To what extent does K-pop represent a social movement?,” and (3) “Do either K-pop music or the artists themselves contribute to fan participation in social advocacy, and if so, how?” I find that K-pop fans do constitute a social movement due to their use of extra-institutional tactics, based on John Fiske’s (1992) concept of fandom as “subversive by design,” Henry Jenkins’ (1992) participatory fan culture framework, and Social Movement Theory (King, 2011). I also further Yoon’s (2017) thesis that pop culture can give those who face a lack of resources and authority a means to challenge the status quo, emphasizing K-pop fans’ innovative use of social media mobilization. By explaining how K-pop and its fans can be understood as a social movement, my research rethinks how we consider K-pop fandom and at the same time encourages K-pop fans to continue their activism work and to expand further. Through a literature review and my own observations framed by theories, I conclude that K-pop fans demonstrate potential to be a powerful force for social change.