Inadequate knowledge about the extent of the coronavirus disease 2019 (COVID-19) epidemic challenges public health response and planning. Most reports of confirmed cases rely on polymerase chain reaction–based testing of symptomatic patients.¹ These estimates of confirmed cases miss individuals who have recovered from infection, with mild or no symptoms, and individuals with symptoms who have not been tested due to limited availability of tests.

Background: Addressing COVID-19 is a pressing health and social concern. To date, many epidemic projections and policies addressing COVID-19 have been designed without seroprevalence data to inform epidemic parameters. We measured the seroprevalence of antibodies to SARS-CoV-2 in a community sample drawn from Santa Clara County. Methods: On April 3-4, 2020, we tested county residents for antibodies to SARS-CoV-2 using a lateral flow immunoassay. Participants were recruited using Facebook ads targeting a sample of individuals living within the county by demographic and geographic characteristics. We estimate weights to adjust our sample to match the zip code, sex, and race/ethnicity distribution within the county. We report both the weighted and unweighted prevalence of antibodies to SARS-CoV-2. We also adjust for test performance characteristics by combining data from 16 independent samples obtained from manufacturer’s data, regulatory submissions, and independent evaluations: 13 samples for specificity (3,324 specimens) and 3 samples for sensitivity (157 specimens). Results: The raw prevalence of antibodies to SARS-CoV-2 in our sample was 1.5% (exact binomial 95CI 1.1-2.0%). Test performance specificity in our data was 99.5% (95CI 99.2-99.7%) and sensitivity was 82.8% (95CI 76.0-88.4%). The unweighted prevalence adjusted for test performance characteristics was 1.2% (95CI 0.7-1.8%). After weighting for population demographics of Santa Clara County, the prevalence was 2.8% (95CI 1.3-4.7%), using bootstrap to estimate confidence bounds. These prevalence point estimates imply that 54,000 (95CI 25,000 to 91,000 using weighted prevalence; 23,000 with 95CI 14,000-35,000 using unweighted prevalence) people were infected in Santa Clara County by early April, many more than the approximately 1,000 confirmed cases at the time of the survey. Conclusions: The estimated population prevalence of SARS-CoV-2 antibodies in Santa Clara County implies that the infection may be much more widespread than indicated by the number of confirmed cases. More studies are needed to improve precision of prevalence estimates. Locally-derived population prevalence estimates should be used to calibrate epidemic and mortality projections.

Background: Elderly patients who leave an acute care hospital after a stroke or a hip fracture may be discharged home, or undergo postacute rehabilitative care in an inpatient rehabilitation facility (IRF) or skilled nursing facility (SNF). Because 15% of Medicare expenditures are for these types of postacute care, it is important to understand their relative costs and the health outcomes they produce. Objective: To assess Medicare payments for and outcomes of patients discharged from acute care to an IRF, a SNF, or home after an inpatient diagnosis of stroke or hip fracture between January 2002 and June 2003. Research Design: This is an observational study based on Medicare administrative data. We adjust for observable differences in patient severity across postacute care sites, and we use instrumental variables estimation to account for unobserved patient selection. Study Outcomes: Mortality, return to community residence, and total Medicare postacute payments by 120 days after acute care discharge. Results: Relative to discharge home, IRFs improve health outcomes for hip fracture patients. SNFs reduce mortality for hip fracture patients, but increase rates of institutionalization for stroke patients. Both sites of care are far more expensive than discharge to home. Conclusions: When there is a choice between IRF and SNF care for stroke and hip fracture patients, the marginal patient is better off going to an IRF for postacute care. However, given the marginal cost of an IRF stay compared with returning home, the gains to these patients should be considered in light of the additional costs.

In the National Pilot Program on Payment Bundling, a subset of Medicare providers will receive a single payment for an episode of acute care in a hospital, followed by postacute care in a skilled nursing or rehabilitation facility, the patient’s home, or other appropriate setting. This article examines the promises and pitfalls of bundled payments and addresses two important design decisions for the pilot: which conditions to include, and how long an episode should be. Our analysis of Medicare data found that hip fracture and joint replacement are good conditions to include in the pilot because they exhibit strong potential for cost savings. In addition, these conditions pose less financial risk for providers than other common ones do, so including them would make participation in the program more appealing to providers. We also found that longer episode lengths captured a higher percentage of costs and hospital readmissions while adding little financial risk. We recommend that the Medicare pilot program test alternative design features to help foster payment innovation throughout the health system.

Traditional fee-for-service (FFS) Medicare’s prospective payment systems for postacute care provide little incentive to coordinate care or control costs. In contrast, Medicare Advantage plans pay f...