RESUMEN
Population-based seroprevalence surveys can provide useful estimates of the number of individuals previously infected with SARS-CoV-2 and still susceptible as well as contribute to better estimates of the case fatality rate and other measures of COVID-19 severity. No serological test is 100% accurate, however, and the standard correction that epidemiologists use to adjust estimates relies on estimates of the test sensitivity and specificity often based on small validation studies. This paper develops a fully Bayesian approach to adjust observed prevalence estimates for sensitivity and specificity. Application to a seroprevalence survey conducted in New York State in 2020 demonstrates that this approach results in more realistic - and narrower - credible interval than the standard sensitivity analysis using confidence interval endpoints. In addition, the model permits incorporating data on the geographical distribution of reported case counts to create informative priors on the cumulative incidence to produce estimates and credible intervals for smaller geographic areas than often can be precisely estimated with seroprevalence surveys.
RESUMEN
ObjectivesPublic health interventions designed to interrupt COVID-19 transmission could have deleterious impacts on primary healthcare access. We sought to identify whether implementation of the nationwide lockdown (shelter-in-place) order in South Africa affected ambulatory clinic visitation in rural Kwa-Zulu Natal (KZN). DesignProspective, longitudinal cohort study SettingData were analyzed from the Africa Health Research Institute Health and Demographic Surveillance System, which includes prospective data capture of clinic visits at eleven primary healthcare clinics in northern KwaZulu-Natal ParticipantsA total of 36,291 individuals made 55,545 clinic visits during the observation period. Exposure of InterestWe conducted an interrupted time series analysis with regression discontinuity methods to estimate changes in outpatient clinic visitation from 60 days before through 35 days after the lockdown period. Outcome MeasuresDaily clinic visitation at ambulatory clinics. In stratified analyses we assessed visitation for the following sub-categories: child health, perinatal care and family planning, HIV services, noncommunicable diseases, and by age and sex strata. ResultsWe found no change in total clinic visits/clinic/day from prior to and during the lockdown (-6.9 visits/clinic/day, 95%CI -17.4, 3.7) or trends in clinic visitation over time during the lockdown period (-0.2, 95%CI -3.4, 3.1). We did detect a reduction in child healthcare visits at the lockdown (-7.2 visits/clinic/day, 95%CI -9.2, -5.3), which was seen in both children <1 and children 1-5. In contrast, we found a significant increase in HIV visits immediately after the lockdown (8.4 visits/clinic/day, 95%CI 2.4, 14.4). No other differences in clinic visitation were found for perinatal care and family planning, non-communicable diseases, or among adult men and women. ConclusionsIn rural KZN, the ambulatory healthcare system was largely resilient during the national-wide lockdown order. A major exception was child healthcare visitation, which declined immediately after the lockdown but began to normalize in the weeks thereafter. Future work should explore efforts to decentralize chronic care for high-risk populations and whether catch-up vaccination programs might be required in the wake of these findings. What is already known on this topic?O_LIPrior disease epidemics have created severe interruptions in access to primary care in sub-Saharan Africa, resulting in increased child and maternal mortality C_LIO_LIData from resource-rich settings and modelling studies have suggested the COVID-19 epidemic and non-pharmacologic measures implemented in response could similarly result in substantial barriers to primary health care access in the region C_LIO_LIWe leveraged a clinical information system in rural KwaZulu-Natal to empirically assess the effect of the COVID-19 epidemic and a nationwide lockdown in South Africa on access to primary care C_LI What this study adds?O_LIAccess to primary healthcare was largely maintained during the most stringent period of the COVID-19 lockdown in South Africa, with the exception of a temporary drop in child health visits C_LIO_LICreative solutions are needed for sustaining child vaccination programs, and protecting high-risk individuals from risk of nosocomial transmission in resource-limited settings C_LI
