RESUMO
ObjectiveTo analyse the impact on hospital admissions for COVID-19 of large-scale, voluntary, public open access rapid testing for SARS-CoV-2 antigen in Liverpool (UK) between 6th November 2020 and 2nd January 2021. DesignSynthetic control analysis comparing hospital admissions for small areas in the intervention population to a group of control areas weighted to be similar in terms of prior COVID-19 hospital admission rates and socio-demographic factors. InterventionCOVID-SMART (Systematic Meaningful Asymptomatic Repeated Testing), a national pilot of large-scale, voluntary rapid antigen testing for people without symptoms of COVID-19 living or working in the City of Liverpool, deployed with the assistance of the British Army from the 6th November 2020 in an unvaccinated population. This pilot informed the UK roll-out of SARS-CoV-2 antigen rapid testing, and similar policies internationally. Main outcome measureWeekly COVID-19 hospital admissions for neighbourhoods in England. ResultsThe intensive introduction of COVID-SMART community testing was associated with a 43% (95% confidence interval: 29% to 57%) reduction in COVID-19 hospital admissions in Liverpool compared to control areas for the initial period of intensive testing with military assistance in national lockdown from 6th November to 3rd December 2020. A 25% (11% to 35%) reduction was estimated across the overall intervention period (6th November 2020 to 2nd January 2021), involving fewer testing centres, before Englands national roll-out of community testing, after adjusting for regional differences in Tiers of COVID-19 restrictions from 3rd December 2020 to 2nd January 2021. ConclusionsThe worlds first voluntary, city-wide SARS-CoV-2 rapid antigen testing pilot in Liverpool substantially reduced COVID-19 hospital admissions. Large scale asymptomatic rapid testing for SARS-CoV-2 can help reduce transmission and prevent hospital admissions. Summary boxO_ST_ABSWhat is already known on this topicC_ST_ABS- Previous studies on managing the spread of SARS-CoV-2 have identified asymptomatic transmission as significant challenges for controlling the pandemic. - Along with non-pharmaceutical measures, many countries rolled out population-based asymptomatic testing programmes to further limit transmission. - Evidence is required on whether large scale voluntary testing of communities for COVID-19 reduces severe disease, by breaking chains of transmission. What this study adds- The findings of this study suggest that large scale rapid antigen testing of communities for SARS-CoV-2, within an agile local public health campaign, can reduce transmission and prevent hospital admissions. - The results indicate that policy makers should integrate such testing into comprehensive, local public health programmes targeting high risk groups, supporting those required to isolate and adapting promptly to prevailing biological, behavioural and environmental circumstances.
RESUMO
BackgroundIn 2020, a second wave of COVID-19 cases unevenly affected places in England leading to the introduction of a tiered system of controls with different geographical areas subject to different levels of restrictions. Whilst previous research has examined the impact of national lockdowns on transmission, there has been limited research examining the marginal effect of differences in localised restrictions or how these effects vary between socioeconomic contexts. We therefore examined how Tier 3 restrictions in England implemented between October-December 2020, which included additional restrictions on the hospitality sector and people meeting outdoors affected COVID-19 case rates, compared to Tier 2 restrictions, and how these effects varied by level of deprivation. MethodsWe used data on weekly reported COVID-19 cases for 7201 neighbourhoods in England and adjusted these for changing case-detection rates to provide an estimate of weekly SARS-CoV-2 infections in each neighbourhood. We identified those areas that entered Tier 3 restrictions at two time points in October and December, and constructed a synthetic control group of similar places that had entered Tier 2 restrictions, using calibration weights to match them on a wide range of covariates that may influence transmission. We then compared the change in weekly infections between those entering Tier 3 to the synthetic control group to estimate the proportional reduction of cases resulting from Tier 3 restrictions compared to Tier 2 restrictions, over a 4-week period. We further used interaction analysis to estimate whether this effect differed based on the level of socioeconomic deprivation in each neighbourhood and whether effects were modified by the prevalence of a new more infectious variant of SARS-CoV-2 (B.1.1.7) in each area. ResultsThe introduction of Tier 3 restrictions in October and December was associated with a 14% (95% CI 10% to 19%) and 20% (95% CI 13% to 29%) reduction in infections respectively, compared to the rates expected if only Tier 2 restrictions had been in place in those areas. We found that effects were similar across levels of deprivation and limited evidence that Tier 3 restrictions had a greater effect in areas where the new more infectious variant was more prevalent. InterpretationAdditional restrictions on hospitality and meeting outdoors introduced in Tier 3 areas in England had a moderate effect on transmission and these restrictions did not appear to increase inequalities, having a similar impact across areas with differing levels of socioeconomic deprivation. Where transmission risks vary between geographical areas a tiered approach of local restrictions on outdoor mixing and hospitality can contribute to control of SARS-CoV-2 and is unlikely to increases inequalities in transmission.
RESUMO
In this paper, we extend our previous work on deformable image registration to inhomogenous tissues. Inhomogenous tissues include the tissues with embedded tumors, which is common in clinical applications. It is a very challenging task since the registration method that works for homogenous tissues may not work well with inhomogenous tissues. The maximum error normally occurs in the regions with tumors and often exceeds the acceptable error threshold. In this paper, we propose a new error correction method with adaptive weighting to reduce the maximum registration error. Our previous fast deformable registration method is used in the inner loop. We have also proposed a new evaluation metric average error of deformation field (AEDF) to evaluate the registration accuracy in regions between vessels and bifurcation points. We have validated the proposed method using liver MR images from human subjects. AEDF results show that the proposed method can greatly reduce the maximum registration errors when compared with the previous method with no adaptive weighting. The proposed method has the potential to be used in clinical applications to reduce registration errors in regions with tumors.
