RESUMEN
For COVID-19, it is vital to understand if quarantines shorter than 14 days can be equally effective with judiciously deployed testing. Here, we develop a mathematical model that quantifies the probability of post-quarantine transmission incorporating testing into travel quarantine, quarantine of traced contacts with an unknown time of infection, and quarantine of cases with a known time of exposure. We find that testing on exit (or entry and exit) can reduce the duration of a 14-day quarantine by 50%, while testing on entry shortens quarantine by at most one day. In a real-world test of our theory applied to offshore oil rig employees, 47 positives were obtained with testing on entry and exit to quarantine, of which 16 had tested negative at entry; preventing an expected nine offshore transmission events that each could have led to outbreaks. We show that appropriately timed testing can make shorter quarantines effective.
Asunto(s)
COVID-19/diagnóstico , Cuarentena , SARS-CoV-2/aislamiento & purificación , COVID-19/epidemiología , COVID-19/transmisión , COVID-19/virología , Trazado de Contacto , Humanos , Modelos Teóricos , Probabilidad , SARS-CoV-2/genética , SARS-CoV-2/fisiología , Factores de TiempoRESUMEN
As economic woes of the COVID-19 pandemic deepen, strategies are being formulated to avoid the need for prolonged stay-at-home orders, while implementing risk-based quarantine, testing, contact tracing and surveillance protocols. Given limited resources and the significant economic, public health, and operational challenges of the current 14-day quarantine recommendation, it is vital to understand if shorter but equally effective quarantine and testing strategies can be deployed. To quantify the probability of post-quarantine transmission upon isolation of a positive test, we developed a mathematical model in which we varied quarantine duration and the timing of molecular tests for three scenarios of entry into quarantine. Specifically, we consider travel quarantine, quarantine of traced contacts with an unknown time if infection, and quarantine of cases with a known time of exposure. With a one-day delay between test and result, we found that testing on exit (or entry and exit) can reduce the duration of a 14-day quarantine by 50%, while testing on entry shortened quarantine by at most one day. Testing on exit more effectively reduces post-quarantine transmission than testing upon entry. Furthermore, we identified the optimal testing date within quarantines of varying duration, finding that testing on exit was most effective for quarantines lasting up to seven days. As a real-world validation of these principles, we analyzed the results of 4,040 SARS CoV-2 RT-PCR tests administered to offshore oil rig employees. Among the 47 positives obtained with a testing on entry and exit strategy, 16 cases that previously tested negative at entry were identified, with no further cases detected among employees following quarantine exit. Moreover, this strategy successfully prevented an expected nine offshore transmission events stemming from cases who had tested negative on the entry test, each one a serious concern for initiating rapid spread and a disabling outbreak in the close quarters of an offshore rig. This successful outcome highlights that appropriately timed testing can make shorter quarantines more effective, thereby minimizing economic impacts, disruptions to operational integrity, and COVID-related public health risks.
RESUMEN
Adherence to oral daily bisphosphonate regimens in postmenopausal osteoporosis is currently suboptimal. Less frequent dosing regimens are likely to improve patient adherence and thus, potentially, patient outcomes. A multicenter, randomized, double-blind, noninferiority study was conducted in 235 women (53-80 yr old; time since menopause >/==" BORDER="0"> 3 yr) with postmenopausal osteoporosis [lumbar spine (L1-L4) bone mineral density (BMD) T-score = -2] to demonstrate the noninferiority of an oral weekly (20 mg) ibandronate regimen compared with an oral daily (2.5 mg) ibandronate regimen. All patients received daily calcium (500 mg) and vitamin D (400 IU). The primary analysis was the relative change in lumbar spine (L1-L4) BMD from baseline after 48 wk in the per- protocol population. Daily and weekly ibandronate significantly increased spinal BMD by 3.47 and 3.53%, respectively, and provided substantial and similar decreases in biochemical markers of bone turnover. In the primary analysis, noninferiority of the weekly regimen to the daily regimen was demonstrated, with the boundary of the one-sided confidence interval, -0.96%, within both the -1.65% prespecified margin and a more stringent margin of -1.10%. These results demonstrate that oral weekly ibandronate provides the same efficacy and safety as oral daily ibandronate in women with postmenopausal osteoporosis.