Protection against the omicron variant from previous SARS-CoV-2 infection

Natural infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) elicits strong protection against reinfection with the B.1.1.7 (alpha),1,2 B.1.351 (beta),1 and B.1.617.2 (delta)3 variants. However, the B.1.1.529 (omicron) variant harbors multiple mutations that can mediate immune evasion. We estimated the effectiveness of previous infection in preventing symptomatic new cases caused by omicron and other SARS-CoV-2 variants in Qatar. In this study, we extracted data regarding coronavirus disease 2019 (Covid-19) laboratory testing, vaccination, clinical infection data, and related demographic details from the national SARS-CoV-2 databases, which include all results of polymerase-chain-reaction (PCR) testing, vaccinations, and hospitalizations and deaths for Covid-19 in Qatar since the start of the pandemic

Fragility Fracture Incidence and Risk in Patients Who Undergone Bone Mineral Density Testing in Qatar: A Retrospective Cohort Study

Background: Osteoporosis and its associated fragility fractures pose a significant public health issue in the elderly population. Additionally, diabetes has been linked to an increased risk of fragility fractures. In Qatar, little is known about the burden of fragility fractures and their association with osteoporosis or diabetes. Aims: Determining the burden of incident fragility fractures, following a bone mineral density (BMD) test, and the effects of having lower BMD levels and being diabetic on the risk of fragility fractures in the population aged fifty and older. Additionally, assessing the impact of database selection for the BMD reference range used to establish osteoporosis diagnosis on fracture risk estimates in the Qatari women subpopulation. Methods: In this retrospective hospital-based cohort study, patients who underwent BMD testing between May 2016 and June 2019 were followed through their health records from the date of the first test until the first fracture or their last encounter (before April 2020), whichever came first. The incidence rate of fractures per 1000 personmonths of follow-up was estimated. Univariate and multivariate Cox proportional hazards regression analyses were performed to determine the effect of BMD and the effect of diabetes on fracture-free survival. Fracture rates among patients with osteoporosis and sensitivity for detecting incident fractures were estimated and compared using the National Health and Nutrition Examination Survey (NHANES) and the Qatari databases. Results: The cohort consisted of 705 patients who had a median follow-up time of 31.03 months (IQR=12.05). The incidence rate was 1.73 (95% CI= (1.23-2.42)). The crude hazard ratio (HR) for fragility fracture per standard deviation reduction in BMD was 1.82 (95% CI= (1.34-2.48)) and 1.93 (95% CI= (1.37-2.71)) when adjusted for age and gender. Compared to not being diabetic, HR for being diabetic was 1.36 (95% CI= (0.69-2.68)). Using the NHANES database yielded higher incidence rates among female patients with osteoporosis and more sensitivity in detecting incident fracture. Conclusion: Among older adults, BMD is a significant predictor for fragility fractures, and the association between diabetes and fractures remains equivocal. The NHANES database is superior to the Qatari database in detecting incident fracture cases among older Qatari women

Population immunity of natural infection, primary-series vaccination, and booster vaccination in Qatar during the COVID-19 pandemic: an observational studyResearch in context

Summary: Background: Waning of natural infection protection and vaccine protection highlight the need to evaluate changes in population immunity over time. Population immunity of previous SARS-CoV-2 infection or of COVID-19 vaccination are defined, respectively, as the overall protection against reinfection or against breakthrough infection at a given point in time in a given population. Methods: We estimated these population immunities in Qatar's population between July 1, 2020 and November 30, 2022, to discern generic features of the epidemiology of SARS-CoV-2. Effectiveness of previous infection, mRNA primary-series vaccination, and mRNA booster (third-dose) vaccination in preventing infection were estimated, month by month, using matched, test-negative, case–control studies. Findings: Previous-infection effectiveness against reinfection was strong before emergence of Omicron, but declined with time after a wave and rebounded after a new wave. Effectiveness dropped after Omicron emergence from 88.3% (95% CI: 84.8–91.0%) in November 2021 to 51.0% (95% CI: 48.3–53.6%) in December 2021. Primary-series effectiveness against infection was 84.0% (95% CI: 83.0–85.0%) in April 2021, soon after introduction of vaccination, before waning gradually to 52.7% (95% CI: 46.5–58.2%) by November 2021. Effectiveness declined linearly by ∼1 percentage point every 5 days. After Omicron emergence, effectiveness dropped from 52.7% (95% CI: 46.5–58.2%) in November 2021 to negligible levels in December 2021. Booster effectiveness dropped after Omicron emergence from 83.0% (95% CI: 65.6–91.6%) in November 2021 to 32.9% (95% CI: 26.7–38.5%) in December 2021, and continued to decline thereafter. Effectiveness of previous infection and vaccination against severe, critical, or fatal COVID-19 were generally >80% throughout the study duration. Interpretation: High population immunity against infection may not be sustained beyond a year, but population immunity against severe COVID-19 is durable with slow waning even after Omicron emergence. Funding: The Biomedical Research Program and the Biostatistics, Epidemiology, and the Biomathematics Research Core, both at Weill Cornell Medicine-Qatar, Ministry of Public Health, Hamad Medical Corporation, Sidra Medicine, Qatar Genome Programme, Qatar University Biomedical Research Center, and Qatar University Internal Grant ID QUCG-CAS-23/24-114

Effects of BA.1/BA.2 subvariant, vaccination, and prior infection on infectiousness of SARS-CoV-2 omicron infections

Compared to BA.1, BA.2 was associated with lower RT-qPCR cycle threshold (Ct) value-3.53 fewer cycles (95% CI: 3.46-3.60), signifying higher infectiousness. This may reflect higher viral load and/or longer duration of infection for BA.2. Natural immunity from previous infection and booster vaccination were associated with less infectious breakthrough infections.The authors are grateful for support from the Biomedical Research Program and the Biostatistics, Epidemiology, and Biomathematics Research Core, both at Weill Cornell Medicine-Qatar, as well as for support provided by the Ministry of Public Health, Hamad Medical Corporation, and Sidra Medicine. The authors are also grateful for the Qatar Genome Programme and Qatar University Biomedical Research Center for institutional support for the reagents needed for the viral genome sequencing. Statements made herein are solely the responsibility of the authors. The funders of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the Articl

Effects of SARS-CoV-2 Alpha, Beta, and Delta variants, age, vaccination, and prior infection on infectiousness of SARS-CoV-2 infections

In 2021, Qatar experienced considerable incidence of SARS-CoV-2 infection that was dominated sequentially by the Alpha, Beta, and Delta variants. Using the cycle threshold (Ct) value of an RT-qPCR-positive test to proxy the inverse of infectiousness, we investigated infectiousness of SARS-CoV-2 infections by variant, age, sex, vaccination status, prior infection status, and reason for testing in a random sample of 18,355 RT-qPCR-genotyped infections. Regression analyses were conducted to estimate associations with the Ct value of RT-qPCR-positive tests. Compared to Beta infections, Alpha and Delta infections demonstrated 2.56 higher Ct cycles (95% CI: 2.35-2.78), and 4.92 fewer cycles (95% CI: 4.67- 5.16), respectively. The Ct value declined gradually with age and was especially high for children <10 years of age, signifying lower infectiousness in small children. Children <10 years of age had 2.18 higher Ct cycles (95% CI: 1.88-2.48) than those 10-19 years of age. Compared to unvaccinated individuals, the Ct value was higher among individuals who had received one or two vaccine doses, but the Ct value decreased gradually with time since the second-dose vaccination. Ct value was 2.07 cycles higher (95% CI: 1.42-2.72) for those with a prior infection than those without prior infection. The Ct value was lowest among individuals tested because of symptoms and was highest among individuals tested as a travel requirement. Delta was substantially more infectious than Beta. Prior immunity, whether due to vaccination or prior infection, is associated with lower infectiousness of breakthrough infections, but infectiousness increases gradually with time since the second-dose vaccination