Clinical Infectious Diseases

BackgroundWe aimed to estimate the burden of antibiotic-nonsusceptible non-bacteremic pneumonia and sinusitis due to Streptococcus pneumoniae (pneumococcus) in US adults ([≥]18 years). MethodsWe estimated antibiotic-nonsusceptible pneumococcal sinusitis and non-bacteremic pneumonia incidence as products of non-bacteremic pneumococcal pneumonia and sinusitis incidence rates, serotype distribution, and serotype-specific antimicrobial nonsusceptibility prevalences by antibiotic class and guidel...

ObjectiveTo compare the frequency of replication-competent virologic rebound with and without nirmatrelvir-ritonavir treatment for acute COVID-19. Secondary aims were to estimate the validity of symptoms to detect rebound and the incidence of emergent nirmatrelvir-resistance mutations after rebound. DesignObservational cohort study. SettingMulticenter healthcare system in Boston, Massachusetts. ParticipantsWe enrolled ambulatory adults with a positive COVID-19 test and/or a prescription for n...

BackgroundHouseholds are a major setting for SARS-CoV-2 infections, but there remains a lack of knowledge regarding the dynamics of viral transmission, particularly in the setting of widespread pre-existing SARS-CoV-2 immunity and evolving variants. MethodsWe conducted a prospective, case-ascertained household transmission study in the greater Boston area in March-July 2022. Anterior nasal swabs, along with clinical and demographic data, were collected for 14 days. Nasal swabs were tested for S...

BackgroundIn the United States, oral nirmatrelvir-ritonavir (Paxlovid) is authorized for use among patients aged [≥]12 years with mild-to-moderate SARS-CoV-2 infection who are at risk for progression to severe COVID-19, including hospitalization. However, effectiveness under current real-world prescribing practices in outpatient settings is unclear. MethodsWe undertook a matched observational cohort study of non-hospitalized cases with SARS-CoV-2 infection to compare outcomes among those who...

II.ImportanceThe U.S. arrival of the Omicron variant led to a rapid increase in SARS-CoV-2 infections. While numerous studies report characteristics of Omicron infections among vaccinated individuals and/or persons with a prior history of infection, comprehensive data describing infections among immunologically naive adults is lacking. ObjectiveTo examine COVID-19 acute and post-acute clinical outcomes among a well-characterized cohort of unvaccinated and previously uninfected adults who contra...

BackgroundThe natural history of SARS-CoV-2 infection and transmission dynamics may have changed as SARS-CoV-2 has evolved and population immunity has shifted. MethodsHousehold contacts, enrolled from two multi-site case-ascertained household transmission studies (April 2020-April 2021 and September 2021-September 2022), were followed for 10-14 days after enrollment with daily collection of nasal swabs and/or saliva for SARS-CoV-2 testing and symptom diaries. SARS-CoV-2 virus lineage was determ...

BackgroundWe estimated vaccine effectiveness (VE) against COVID-19 and long COVID during pre-Omicron and Omicron periods, by number of doses and prior infection history. MethodsWe combined survey information from a cohort of healthcare workers in Quebec, Canada, with immunization registry and laboratory administrative data. We defined COVID-19 cases as symptomatic laboratory-confirmed infections and long COVID as self-reported symptoms persisting [≥]12 weeks. We assessed VE against COVID-19 ...

ImportanceThe frequency and characteristics of post-acute sequelae of SARS-CoV-2 infection (PASC) may vary by SARS-CoV-2 variant. ObjectiveTo characterize PASC-related conditions among individuals likely infected by the ancestral strain in 2020 and individuals likely infected by the Delta variant in 2021. DesignRetrospective cohort study of electronic medical record data for approximately 27 million patients from March 1, 2020-November 30, 2021. SettingHealthcare facilities in New York and Fl...

BackgroundThe incidence of respiratory syncytial virus (RSV) dropped markedly early in the COVID-19 pandemic, followed by a resurgence with heightened case counts. The "immunity debt" hypothesis proposes that the RSV-naive pediatric population increased during the period of low transmission, resulting in a subsequent increased risk of infection. However, the evidence supporting this hypothesis is limited, and no studies have comprehensively evaluated the role of changing respiratory viral testin...

BackgroundRespiratory Syncytial Virus (RSV) can cause severe respiratory disease. While risks among older adults are well established, less is known about RSV severity in younger adults with chronic conditions. MethodsA retrospective cohort study using U.S. commercial and Medicaid claims data was conducted to evaluate outcomes in adults aged 18-59 with medically attended RSV (MA-RSV) in 2022-24. Chronic conditions were assessed during a 12-month baseline period prior to the MA-RSV. Severe outco...

BackgroundThe District of Columbia (DC), a major metropolitan area, continues to see community transmission of SARS-CoV-2. While serologic testing does not indicate current SARS-CoV-2 infection, it can indicate prior infection and help inform local policy and health guidance. The DC Department of Health (DC Health) conducted a community-based survey to estimate DCs SARS-CoV-2 seroprevalence and identify seropositivity-associated factors. MethodsA mixed-methods cross-sectional serology survey wa...

BackgroundThe first RSV vaccines for adults 60 years and older were approved prior to the 2023-2024 respiratory virus season. This study used data from adults 60 years and older, enrolled into the Community Vaccine Effectiveness (CoVE) cohort study, in Michigan, U.S.A, to evaluate RSV vaccine effectiveness (VE) and antibody correlates of protection. MethodsA Cox proportional hazards model was used to compare incidence of symptomatic / all RSV infections in those vaccinated versus unvaccinated. ...

Approximately 20-40% of SARS-CoV-2 infection is asymptomatic; however, data are limited on drivers of such infection. Among over 730,000 SARS-CoV-2 test results in Los Angeles between August-October, 2020, we found heterogenous frequencies of asymptomatic infection among various sup-populations. Further research is needed to delineate drivers of asymptomatic SARS-CoV-2 infection.

IMPORTANCENirsevimab, a long-acting monoclonal antibody, has demonstrated efficacy against RSV-related lower respiratory tract infections (LRTIs) in clinical trials. Post-licensure monitoring is essential to confirm these benefits in real-world settings. OBJECTIVETo evaluate the real-world effectiveness of nirsevimab against medically attended RSV infections in infants and to assess how effectiveness varies by disease severity, dosage, and time since immunization. DESIGN, SETTING, AND PARTICIP...

BackgroundDuring the 2024-25 season, a universal infant nirsevimab program was publicly funded in Quebec, Canada. We estimated effectiveness, number-needed-to-immunize (NNI) and impact against severe respiratory syncytial virus (RSV) outcomes. MethodsWe conducted a test-negative study among nirsevimab-eligible children RSV-tested during ER consultation or hospitalization between October 1st, 2024 and March 3st, 2025. Eligible children were healthy-term and born during the RSV season (at-birth g...

BackgroundThe primary objective of influenza immunization programs is to reduce the risk and burden of severe outcomes. To inform optimal program strategies, we monitored influenza hospitalizations over several seasons of varying subtype predominance, stratified by age, comorbidity and vaccination status. MethodsWe assembled data from an active hospital-based surveillance network involving systematic swabbing and PCR-confirmation of influenza virus infection by type/subtype during peak-weeks of...

BackgroundIncreased reinfection rates with SARS-CoV-2 have recently been reported, with some locations basing reinfection on a second positive PCR test at least 90 days after initial infection. MethodsWe identified cases where patients had two positive tests for SARS-CoV-2 and evaluated which of these had been sequenced as part of our surveillance efforts, and evaluated sequencing and clinical data. Results750 patients (920 samples) had a positive test at least 90 days after the initial test. ...

ImportanceRecent CDC COVID-19 isolation guidance for non-immunocompromised individuals with asymptomatic or mild infection allows ending isolation after 5 days if asymptomatic or afebrile with improving symptoms. The role of rapid antigen testing in further characterizing the risk of viral transmission to others is unclear. ObjectiveUnderstand rates of rapid antigen test (RAT) positivity after day 5 from a positive COVID-19 test and the relationship of this result to symptoms and viral culture....

ObjectiveReal-world data on the effectiveness of boosters against COVID-19, especially as new variants continue to emerge, is limited. It is our objective to assess demographic, clinical, and outcome variables of patients requiring hospitalization for severe SARS-CoV-2 infection comparing fully vaccinated and boosted (FV&B) and unvaccinated (UV) patients. MethodsThis multicenter observational cohort analysis compared demographic, clinical, and outcome variables in FV&B and UV adults hospitalize...

IntroductionMore than 93,000 cases of coronavirus disease (COVID-19) have been reported worldwide. We describe the epidemiology, clinical course, and virologic characteristics of the first 12 U.S. patients with COVID-19. MethodsWe collected demographic, exposure, and clinical information from 12 patients confirmed by CDC during January 20-February 5, 2020 to have COVID-19. Respiratory, stool, serum, and urine specimens were submitted for SARS-CoV-2 rRT-PCR testing, virus culture, and whole geno...