Relative Effectiveness of Coronavirus Disease 2019 Vaccination and Booster Dose Combinations Among 18.9 Million Vaccinated Adults During the Early Severe Acute Respiratory Syndrome Coronavirus 2 Omicron Period-United States, 1 January 2022 to 31 March 2022.

BACKGROUND: Small sample sizes have limited prior studies' ability to capture severe COVID-19 outcomes, especially among Ad26.COV2.S vaccine recipients. This study of 18.9 million adults aged ≥18 years assessed relative vaccine effectiveness (rVE) in three recipient cohorts: (1) primary Ad26.COV2.S vaccine and Ad26.COV2.S booster (2 Ad26.COV2.S), (2) primary Ad26.COV2.S vaccine and mRNA booster (Ad26.COV2.S+mRNA), (3) two doses of primary mRNA vaccine and mRNA booster (3 mRNA). METHODS: We analyzed two de-identified datasets linked using privacy-preserving record linkage (PPRL): insurance claims and retail pharmacy COVID-19 vaccination data. We assessed the presence of COVID-19 diagnosis during January 1-March 31, 2022 in: (1) any claim, (2) outpatient claim, (3) emergency department (ED) claim, (4) inpatient claim, and (5) inpatient claim with intensive care unit (ICU) admission. rVE for each outcome comparing three recipient cohorts (reference: two Ad26.COV2.S doses) was estimated from adjusted Cox proportional hazards models. RESULTS: Compared with two Ad26.COV2.S doses, Ad26.COV2.S+mRNA and three mRNA doses were more effective against all COVID-19 outcomes, including 57% (95% CI: 52-62) and 62% (95% CI: 58-65) rVE against an ED visit; 44% (95% CI: 34-52) and 54% (95% CI: 48-59) rVE against hospitalization; and 48% (95% CI: 22-66) and 66% (95% CI: 53-75) rVE against ICU admission, respectively. CONCLUSIONS: This study demonstrated that Ad26.COV2.S + mRNA doses were as good as three doses of mRNA, and better than two doses of Ad26.COV2.S. Vaccination continues to be an important preventive measure for reducing the public health impact of COVID-19.

Mortality Risk Among Patients Hospitalized Primarily for COVID-19 During the Omicron and Delta Variant Pandemic Periods - United States, April 2020-June 2022.

The risk for COVID-19-associated mortality increases with age, disability, and underlying medical conditions (1). Early in the emergence of the Omicron variant of SARS-CoV-2, the virus that causes COVID-19, mortality among hospitalized COVID-19 patients was lower than that during previous pandemic peaks (2-5), and some health authorities reported that a substantial proportion of COVID-19 hospitalizations were not primarily for COVID-19-related illness,* which might account for the lower mortality among hospitalized patients. Using a large hospital administrative database, CDC assessed in-hospital mortality risk overall and by demographic and clinical characteristics during the Delta (July-October 2021), early Omicron (January-March 2022), and later Omicron (April-June 2022) variant periods† among patients hospitalized primarily for COVID-19. Model-estimated adjusted mortality risk differences (aMRDs) (measures of absolute risk) and adjusted mortality risk ratios (aMRRs) (measures of relative risk) for in-hospital death were calculated comparing the early and later Omicron periods with the Delta period. Crude mortality risk (cMR) (deaths per 100 patients hospitalized primarily for COVID-19) was lower during the early Omicron (13.1) and later Omicron (4.9) periods than during the Delta (15.1) period (p<0.001). Adjusted mortality risk was lower during the Omicron periods than during the Delta period for patients aged ≥18 years, males and females, all racial and ethnic groups, persons with and without disabilities, and those with one or more underlying medical conditions, as indicated by significant aMRDs and aMRRs (p<0.05). During the later Omicron period, 81.9% of in-hospital deaths occurred among adults aged ≥65 years and 73.4% occurred among persons with three or more underlying medical conditions. Vaccination, early treatment, and appropriate nonpharmaceutical interventions remain important public health priorities for preventing COVID-19 deaths, especially among persons most at risk.

Post-COVID-19 Symptoms and Conditions Among Children and Adolescents - United States, March 1, 2020-January 31, 2022.

Post-COVID-19 (post-COVID) symptoms and conditions* are new, recurring, or ongoing health problems that occur 4 or more weeks after infection with SARS-CoV-2 (the virus that causes COVID-19). Previous studies have characterized and estimated the incidence of post-COVID conditions among adults (1,2), but data among children and adolescents are limited (3-8). Using a large medical claims database, CDC assessed nine potential post-COVID signs and symptoms (symptoms) and 15 potential post-COVID conditions among 781,419 U.S. children and adolescents aged 0-17 years with laboratory-confirmed COVID-19 (patients with COVID-19) compared with 2,344,257 U.S. children and adolescents without recognized COVID-19 (patients without COVID-19) during March 1, 2020-January 31, 2022. The analysis identified several symptoms and conditions with elevated adjusted hazard ratios among patients with COVID-19 (compared with those without). The highest hazard ratios were recorded for acute pulmonary embolism (adjusted hazard ratio [aHR] = 2.01), myocarditis and cardiomyopathy (1.99), venous thromboembolic event (1.87), acute and unspecified renal failure (1.32), and type 1 diabetes (1.23), all of which were rare or uncommon in this study population. Conversely, symptoms and conditions that were most common in this study population had lower aHRs (near or below 1.0). Patients with COVID-19 were less likely than were patients without to experience respiratory signs and symptoms, symptoms of mental conditions, muscle disorders, neurological conditions, anxiety and fear-related disorders, mood disorders, and sleeping disorders. COVID-19 prevention strategies, including vaccination for all eligible children and adolescents, are critical to prevent SARS-CoV-2 infection and subsequent illness, including post-COVID symptoms and conditions (9).

SARS-CoV-2 Convalescent Sera Binding and Neutralizing Antibody Concentrations Compared with COVID-19 Vaccine Efficacy Estimates against Symptomatic Infection.

Previous COVID-19 vaccine efficacy (VE) studies have estimated neutralizing and binding antibody concentrations that correlate with protection from symptomatic infection; how these estimates compare to those generated in response to SARS-CoV-2 infection is unclear. Here, we assessed quantitative neutralizing and binding antibody concentrations using standardized SARS-CoV-2 assays on 3,067 serum specimens collected during 27 July 2020 to 27 August 2020 from COVID-19-unvaccinated persons with detectable anti-SARS-CoV-2 antibodies. Neutralizing and binding antibody concentrations were severalfold lower in the unvaccinated study population compared to published concentrations at 28 days postvaccination. In this convenience sample, ~88% of neutralizing and ~63 to 86% of binding antibody concentrations met or exceeded concentrations associated with 70% COVID-19 VE against symptomatic infection; ~30% of neutralizing and 1 to 14% of binding antibody concentrations met or exceeded concentrations associated with 90% COVID-19 VE. Our study not only supports observations of infection-induced immunity and current recommendations for vaccination postinfection to maximize protection against COVID-19, but also provides a large data set of pre-COVID-19 vaccination anti-SARS-CoV-2 antibody concentrations that will serve as an important comparator in the current setting of vaccine-induced and hybrid immunity. As new SARS-CoV-2 variants emerge and displace circulating virus strains, we recommend that standardized binding antibody assays that include spike protein-based antigens be utilized to estimate antibody concentrations correlated with protection from COVID-19. These estimates will be helpful in informing public health guidance, such as the need for additional COVID-19 vaccine booster doses to prevent symptomatic infection. IMPORTANCE Although COVID-19 vaccine efficacy (VE) studies have estimated antibody concentrations that correlate with protection from COVID-19, how these estimates compare to those generated in response to SARS-CoV-2 infection is unclear. We assessed quantitative neutralizing and binding antibody concentrations using standardized assays on serum specimens collected from COVID-19-unvaccinated persons with detectable antibodies. We found that most unvaccinated persons with qualitative antibody evidence of prior infection had quantitative antibody concentrations that met or exceeded concentrations associated with 70% VE against COVID-19. However, only a small proportion had antibody concentrations that met or exceeded concentrations associated with 90% VE, suggesting that persons with prior COVID-19 would benefit from vaccination to maximize protective antibody concentrations against COVID-19.

COVID-19 Cases and Hospitalizations Among Medicare Beneficiaries With and Without Disabilities - United States, January 1, 2020-November 20, 2021.

Approximately 27% of adults in the United States live with a disability,* some of whom qualify for Medicare benefits. Persons with disabilities are at increased risk for severe COVID-19-associated outcomes compared with the general population (1); however, existing studies have limited generalizability† or only pertain to a specific disability (e.g., intellectual) (2). Older age is also associated with COVID-19-associated hospitalization and death, but the extent to which age might contribute to increased risk for severe COVID-19-associated outcomes among persons with disabilities is unknown (3). To describe the impact of COVID-19 on persons with disabilities and whether and how age contributes to disease rates, CDC assessed COVID-19 cases and hospitalizations during January 2020-November 2021, among Centers for Medicare & Medicaid Services (CMS) Medicare beneficiaries aged ≥18 years who were either eligible because of a disability (disability-eligible§) or only eligible because of age ≥65 years (age-eligible). COVID-19 incidence and hospitalization rates were higher in the disability-eligible group (10,978 and 3,148 per 100,000 population, respectively) throughout the study period compared with the age-eligible group (8,102 and 2,129 per 100,000 population, respectively). Both COVID-19 incidence and hospitalization rates increased with age in both disability- and age-eligible beneficiaries. American Indian or Alaska Native (AI/AN) persons had the highest disability-eligible (4,962 per 100,000) and age-eligible (5,024 per 100,000) hospitalization rates. Among all other racial and ethnic groups, hospitalization rates were higher among disability-eligible than among age-eligible patients. COVID-19 incidence and hospitalization rates among disability-eligible Medicare beneficiaries were disproportionally higher than rates among age-eligible beneficiaries. Collection of disability status as a core demographic variable in public health surveillance data and identification, as well as the addition of disability questions in other existing data sources can guide research and development of interventions for persons with disabilities. Efforts to increase access to and use of COVID-19 prevention and treatment strategies, including activities that support equitable vaccine access regardless of the substantial challenges that older adults and persons with disability face, are critical to reducing severe COVID-19-associated outcomes among these groups.

Trends in Acute Hepatitis of Unspecified Etiology and Adenovirus Stool Testing Results in Children - United States, 2017-2022.

In November 2021, CDC was notified of a cluster of previously healthy children with hepatitis of unknown etiology evaluated at a single U.S. hospital (1). On April 21, 2022, following an investigation of this cluster and reports of similar cases in Europe (2,3), a health advisory* was issued requesting U.S. providers to report pediatric cases† of hepatitis of unknown etiology to public health authorities. In the United States and Europe, many of these patients have also received positive adenovirus test results (1,3). Typed specimens have indicated adenovirus type 41, which typically causes gastroenteritis (1,3). Although adenovirus hepatitis has been reported in immunocompromised persons, adenovirus is not a recognized cause of hepatitis in healthy children (4). Because neither acute hepatitis of unknown etiology nor adenovirus type 41 is reportable in the United States, it is unclear whether either has recently increased above historical levels. Data from four sources were analyzed to assess trends in hepatitis-associated emergency department (ED) visits and hospitalizations, liver transplants, and adenovirus stool testing results among children in the United States. Because of potential changes in health care-seeking behavior during 2020-2021, data from October 2021-March 2022 were compared with a pre-COVID-19 pandemic baseline. These data do not suggest an increase in pediatric hepatitis or adenovirus types 40/41 above baseline levels. Pediatric hepatitis is rare, and the relatively low weekly and monthly counts of associated outcomes limit the ability to interpret small changes in incidence. Ongoing assessment of trends, in addition to enhanced epidemiologic investigations, will help contextualize reported cases of acute hepatitis of unknown etiology in U.S. children.

Risk for Newly Diagnosed Diabetes >30 Days After SARS-CoV-2 Infection Among Persons Aged <18 Years - United States, March 1, 2020-June 28, 2021.

The COVID-19 pandemic has disproportionately affected people with diabetes, who are at increased risk of severe COVID-19.* Increases in the number of type 1 diabetes diagnoses (1,2) and increased frequency and severity of diabetic ketoacidosis (DKA) at the time of diabetes diagnosis (3) have been reported in European pediatric populations during the COVID-19 pandemic. In adults, diabetes might be a long-term consequence of SARS-CoV-2 infection (4-7). To evaluate the risk for any new diabetes diagnosis (type 1, type 2, or other diabetes) >30 days† after acute infection with SARS-CoV-2 (the virus that causes COVID-19), CDC estimated diabetes incidence among patients aged <18 years (patients) with diagnosed COVID-19 from retrospective cohorts constructed using IQVIA health care claims data from March 1, 2020, through February 26, 2021, and compared it with incidence among patients matched by age and sex 1) who did not receive a COVID-19 diagnosis during the pandemic, or 2) who received a prepandemic non-COVID-19 acute respiratory infection (ARI) diagnosis. Analyses were replicated using a second data source (HealthVerity; March 1, 2020-June 28, 2021) that included patients who had any health care encounter possibly related to COVID-19. Among these patients, diabetes incidence was significantly higher among those with COVID-19 than among those 1) without COVID-19 in both databases (IQVIA: hazard ratio [HR] = 2.66, 95% CI = 1.98-3.56; HealthVerity: HR = 1.31, 95% CI = 1.20-1.44) and 2) with non-COVID-19 ARI in the prepandemic period (IQVIA, HR = 2.16, 95% CI = 1.64-2.86). The observed increased risk for diabetes among persons aged <18 years who had COVID-19 highlights the importance of COVID-19 prevention strategies, including vaccination, for all eligible persons in this age group,§ in addition to chronic disease prevention and management. The mechanism of how SARS-CoV-2 might lead to incident diabetes is likely complex and could differ by type 1 and type 2 diabetes. Monitoring for long-term consequences, including signs of new diabetes, following SARS-CoV-2 infection is important in this age group.

Decreases in Hepatitis C Testing and Treatment During the COVID-19 Pandemic.

INTRODUCTION: The COVID-19 pandemic has disrupted healthcare services, reducing opportunities to conduct routine hepatitis C virus antibody screening, clinical care, and treatment. Therefore, people living with undiagnosed hepatitis C virus during the pandemic may later become identified at more advanced stages of the disease, leading to higher morbidity and mortality rates. Further, unidentified hepatitis C virus-infected individuals may continue to unknowingly transmit the virus to others. METHODS: To assess the impact of the COVID-19 pandemic, data were evaluated from a large national reference clinical laboratory and from national estimates of dispensed prescriptions for hepatitis C virus treatment. Investigators estimated the average number of hepatitis C virus antibody tests, hepatitis C virus antibody-positive test results, and hepatitis C virus RNA-positive test results by month in January-July for 2018 and 2019, compared with the same months in 2020. To assess the impact of hepatitis C virus treatment, dispensed hepatitis C virus direct-acting antiretroviral medications were examined for the same time periods. Statistical analyses of trends were performed using negative binomial models. RESULTS: Compared with the 2018 and 2019 months, hepatitis C virus antibody testing volume decreased 59% during April 2020 and rebounded to a 6% reduction in July 2020. The number of hepatitis C virus RNA-positive results fell by 62% in March 2020 and remained 39% below the baseline by July 2020. For hepatitis C virus treatment, prescriptions decreased 43% in May, 37% in June, and 38% in July relative to the corresponding months in 2018 and 2019. CONCLUSIONS: During the COVID-19 pandemic, continued public health messaging, interventions and outreach programs to restore hepatitis C virus testing and treatment to prepandemic levels, and maintenance of public health efforts to eliminate hepatitis C infections remain important.

Changes in Emergency Medical Services Before and During the COVID-19 Pandemic in the United States, January 2018-December 2020.

BACKGROUND: As a result of the continuing surge of coronavirus disease 2019 (COVID-19), many patients have delayed or missed routine screening and preventive services. Medical conditions, such as coronary heart disease, mental health issues, and substance use disorder, may be identified later, leading to increases in patient morbidity and mortality. METHODS: National Emergency Medical Services Information System data were used to assess 911 emergency medical services (EMS) activations during 2018-2020. For specific activation types, the percentage of total activations was calculated per week, and Joinpoint analysis was used to identify changes over time. RESULTS: Since March 2020, the number of 911 EMS activations has decreased, while the percentages of on-scene death, cardiac arrest, and opioid use/overdose EMS activations were higher than prepandemic levels. During the early pandemic period, percentages of total EMS activations increased for on-scene death (from 1.3% to 2.4% during weeks 11-15), cardiac arrest (from 1.3% to 2.2% during weeks 11-15), and opioid use/overdose (from 0.6% to 1.1% during weeks 8-18). The percentages then declined but remained above prepandemic levels through calendar week 52. CONCLUSIONS: The COVID-19 pandemic has indirect consequences, such as relative increases in EMS activations for cardiac events and opioid use/overdose, possibly linked to disruptions is healthcare access and health-seeking behaviors. Increasing telehealth visits and other opportunities for patient-provider touch points for chronic disease and substance use disorders that emphasize counseling, preventive care, and expanded access to medications can disrupt delayed care-seeking during the pandemic and potentially prevent premature death.

Hydroxychloroquine and Chloroquine Prescribing Patterns by Provider Specialty Following Initial Reports of Potential Benefit for COVID-19 Treatment - United States, January-June 2020.

Hydroxychloroquine and chloroquine, primarily used to treat autoimmune diseases and to prevent and treat malaria, received national attention in early March 2020, as potential treatment and prophylaxis for coronavirus disease 2019 (COVID-19) (1). On March 20, the Food and Drug Administration (FDA) issued an emergency use authorization (EUA) for chloroquine phosphate and hydroxychloroquine sulfate in the Strategic National Stockpile to be used by licensed health care providers to treat patients hospitalized with COVID-19 when the providers determine the potential benefit outweighs the potential risk to the patient.* Following reports of cardiac and other adverse events in patients receiving hydroxychloroquine for COVID-19 (2), on April 24, 2020, FDA issued a caution against its use† and on June 15, rescinded its EUA for hydroxychloroquine from the Strategic National Stockpile.§ Following the FDA's issuance of caution and EUA rescindment, on May 12 and June 16, the federal COVID-19 Treatment Guidelines Panel issued recommendations against the use of hydroxychloroquine or chloroquine to treat COVID-19; the panel also noted that at that time no medication could be recommended for COVID-19 pre- or postexposure prophylaxis outside the setting of a clinical trial (3). However, public discussion concerning the effectiveness of these drugs on outcomes of COVID-19 (4,5), and clinical trials of hydroxychloroquine for prophylaxis of COVID-19 continue.¶ In response to recent reports of notable increases in prescriptions for hydroxychloroquine or chloroquine (6), CDC analyzed outpatient retail pharmacy transaction data to identify potential differences in prescriptions dispensed by provider type during January-June 2020 compared with the same period in 2019. Before 2020, primary care providers and specialists who routinely prescribed hydroxychloroquine, such as rheumatologists and dermatologists, accounted for approximately 97% of new prescriptions. New prescriptions by specialists who did not typically prescribe these medications (defined as specialties accounting for ≤2% of new prescriptions before 2020) increased from 1,143 prescriptions in February 2020 to 75,569 in March 2020, an 80-fold increase from March 2019. Although dispensing trends are returning to prepandemic levels, continued adherence to current clinical guidelines for the indicated use of these medications will ensure their availability and benefit to patients for whom their use is indicated (3,4), because current data on treatment and pre- or postexposure prophylaxis for COVID-19 indicate that the potential benefits of these drugs do not appear to outweigh their risks.

Factors Associated With Testing for Hepatitis C Infections Among a Commercially Insured Population of Persons With HIV, United States 2008-2016.

BACKGROUND: Hepatitis C virus (HCV) infection is an important public health problem among people with HIV. People with HIV who are coinfected with HCV infection are at increased risk for cirrhosis, liver failure, and hepatitis C-related mortality; as such, national guidelines recommend that persons with HIV be tested for HCV infection. METHODS: Data from the 2003-2017 IBM Watson Health MarketScan database were used for this study. We used diagnostic, procedural, and drug codes to identify patients with ≥1 inpatient or outpatient medical claim of HIV diagnosis. Patients with prior HIV or hepatitis C diagnoses were excluded. We calculated hepatitis C testing rates among newly diagnosed HIV-infected persons within 12 months of the initial HIV diagnosis date (January 1, 2008-December 31, 2016). We used Poisson regression to identify the factors associated with hepatitis C testing. Lastly, we assessed hepatitis C testing trends using the Cochran-Armitage test. RESULTS: The prevalence of testing for hepatitis C in newly identified persons with HIV (n = 46 277) was 50% within 12 months of the index HIV diagnosis. From 2008 to 2017, the testing rate increased by 13%. Significant predictors of hepatitis C testing were age, sex, and urbanicity. Women with HIV were less likely to have been tested compared with men (relative risk, 0.79; 95% CI, 0.77-0.81). Only 40% of patients between 50 and 59 years of age were tested for hepatitis C within 12 months of the index HIV diagnosis, while 56% of persons with HIV aged 20-29 years were tested for hepatitis C. CONCLUSIONS: Overall, 50% of newly diagnosed HIV patients were tested for hepatitis C within 12 months of HIV diagnosis. Although there were increases in hepatitis C testing rates over the study period, there were missed opportunities to detect HCV infection among people newly diagnosed with HIV.

Human Immunodeficiency Virus and Hepatitis C Virus Infection Testing Among Commercially Insured Persons Who Inject Drugs, United States, 2010-2017.

BACKGROUND: We assessed prevalence of testing for human immunodeficiency virus (HIV) and hepatitis C virus (HCV) infection among persons who inject drugs (PWID). METHODS: Using a nationwide health insurance database for claims paid during 2010-2017, we identified PWID by using codes from the International Classification of Diseases, Current Procedural Terminology, and National Drug Codes directory. We then estimated the percentage of PWIDs tested for HIV or HCV within 1 year of an index encounter, and we used multivariate logistic regression models to assess demographic and clinical factors associated with testing. RESULTS: Of 844 242 PWIDs, 71 938 (8.5%) were tested for HIV and 65 188 (7.7%) were tested for HCV infections. Missed opportunities were independently associated with being male (odds ratios [ORs]: HIV, 0.50 [95% confidence interval {CI}, 0.49-0.50], P < .001; HCV, 0.66 [95% CI, 0.65-0.72], P < .001), rural residence (ORs: HIV, 0.67 [95% CI, 0.65-0.69], P < .001; HCV, 0.75 [95% CI, 0.73-0.77], P < .001), and receiving services for skin infections or endocarditis (adjusted ORs: HIV, 0.91 [95% CI, 0.87-0.95], P < .001; HCV, 0.90 [95% CI, 0.86-0.95], P < .001). CONCLUSIONS: Approximately 90% of presumed PWIDs missed opportunities for HIV or HCV testing, especially male rural residents with claims for skin infections or endocarditis, commonly associated with injection drug use.

Metagenomic analyses of alcohol induced pathogenic alterations in the intestinal microbiome and the effect of Lactobacillus rhamnosus GG treatment.

Enteric dysbiosis plays an essential role in the pathogenesis of alcoholic liver disease (ALD). Detailed characterization of the alterations in the gut microbiome is needed for understanding their pathogenic role in ALD and developing effective therapeutic approaches using probiotic supplementation. Mice were fed liquid Lieber-DeCarli diet without or with alcohol (5% v/v) for 6 weeks. A subset of mice were administered the probiotic Lactobacillus rhamnosus GG (LGG) from 6 to 8 weeks. Indicators of intestinal permeability, hepatic steatosis, inflammation and injury were evaluated. Metagenomic analysis of the gut microbiome was performed by analyzing the fecal DNA by amplification of the V3-V5 regions of the 16S rRNA gene and large-scale parallel pyrosequencing on the 454 FLX Titanium platform. Chronic ethanol feeding caused a decline in the abundance of both Bacteriodetes and Firmicutes phyla, with a proportional increase in the gram negative Proteobacteria and gram positive Actinobacteria phyla; the bacterial genera that showed the biggest expansion were the gram negative alkaline tolerant Alcaligenes and gram positive Corynebacterium. Commensurate with the qualitative and quantitative alterations in the microbiome, ethanol caused an increase in plasma endotoxin, fecal pH, hepatic inflammation and injury. Notably, the ethanol-induced pathogenic changes in the microbiome and the liver were prevented by LGG supplementation. Overall, significant alterations in the gut microbiome over time occur in response to chronic alcohol exposure and correspond to increases in intestinal barrier dysfunction and development of ALD. Moreover, the altered bacterial communities of the gut may serve as significant therapeutic target for the prevention/treatment of chronic alcohol intake induced intestinal barrier dysfunction and liver disease.

Deep resequencing reveals excess rare recent variants consistent with explosive population growth.

Accurately determining the distribution of rare variants is an important goal of human genetics, but resequencing of a sample large enough for this purpose has been unfeasible until now. Here, we applied Sanger sequencing of genomic PCR amplicons to resequence the diabetes-associated genes KCNJ11 and HHEX in 13,715 people (10,422 European Americans and 3,293 African Americans) and validated amplicons potentially harbouring rare variants using 454 pyrosequencing. We observed far more variation (expected variant-site count ∼578) than would have been predicted on the basis of earlier surveys, which could only capture the distribution of common variants. By comparison with earlier estimates based on common variants, our model shows a clear genetic signal of accelerating population growth, suggesting that humanity harbours a myriad of rare, deleterious variants, and that disease risk and the burden of disease in contemporary populations may be heavily influenced by the distribution of rare variants.