Daily use of lateral flow devices by contacts of confirmed COVID-19 cases to enable exemption from isolation compared with standard self-isolation to reduce onward transmission of SARS-CoV-2 in England: a randomised, controlled, non-inferiority trial

Non-pharmaceutical interventions to reduce COVID-19 transmission in the UK: a rapid mapping review and interactive evidence gap map

BACKGROUND

Non-pharmaceutical interventions (NPIs) were crucial in the response to the COVID-19 pandemic, although uncertainties about their effectiveness remain. This work aimed to better understand the evidence generated during the pandemic on the effectiveness of NPIs implemented in the UK.

METHODS

We conducted a rapid mapping review (search date: 1 March 2023) to identify primary studies reporting on the effectiveness of NPIs to reduce COVID-19 transmission. Included studies were displayed in an interactive evidence gap map.

RESULTS

After removal of duplicates, 11 752 records were screened. Of these, 151 were included, including 100 modelling studies but only 2 randomized controlled trials and 10 longitudinal observational studies.Most studies reported on NPIs to identify and isolate those who are or may become infectious, and on NPIs to reduce the number of contacts. There was an evidence gap for hand and respiratory hygiene, ventilation and cleaning.

CONCLUSIONS

Our findings show that despite the large number of studies published, there is still a lack of robust evaluations of the NPIs implemented in the UK. There is a need to build evaluation into the design and implementation of public health interventions and policies from the start of any future pandemic or other public health emergency.

The evaluation of a rapid microfluidic immunofluorescence antigen test in detecting the infectiousness of COVID-19 patients

BACKGROUND

A test-based strategy against coronavirus disease 2019 (COVID-19) is one of the measures to assess the need for isolation and prevention of infection. However, testing with high sensitivity methods, such as quantitative RT-PCR, leads to unnecessary isolation, whereas the lateral flow antigen test shows low sensitivity and false negative results. The purpose of this study was to evaluate the performance of the LumiraDx SARS-CoV-2 Ag test (Lumira Ag), a rapid microfluidic immunofluorescence method, in assessing infectivity.

METHODS

This study was performed from March 2022 to July 2022. A pair of nasopharyngeal swab samples were obtained from each patient with mild COVID-19. One swab was used for Lumira Ag testing, and the other for quantitative RT-PCR testing and virus culture.

RESULTS

A total of 84 patients were included in the study. Among them, PCR, Lumira Ag test, and virus culture indicated positivity for 82, 66, and 24 patients, respectively. When comparing the Lumira Ag test to virus culture, its sensitivity was 100.0% (24/24), specificity, 30.0% (18/60); positive predictive value, 36.3% (24/66); and negative predictive value (NPV), 100.0% (18/18). The positive sample for virus culture was observed until the ninth day from the onset of symptoms, while the Lumira Ag test was observed until day 11.

CONCLUSIONS

The Lumira Ag test showed high sensitivity and NPV (100% each) compared to virus culture. A test-based strategy using the Lumira Ag test can effectively exclude COVID-19 infectiousness.

Effectiveness of testing, contact tracing and isolation interventions among the general population on reducing transmission of SARS-CoV-2: a systematic review

We conducted a systematic literature review of general population testing, contact tracing, case isolation and contact quarantine interventions to assess their effectiveness in reducing SARS-CoV-2 transmission, as implemented in real-world settings. We designed a broad search strategy and aimed to identify peer-reviewed studies of any design provided there was a quantitative measure of effectiveness on a transmission outcome. Studies that assessed the effect of testing or diagnosis on disease outcomes via treatment, but did not assess a transmission outcome, were not included. We focused on interventions implemented among the general population rather than in specific settings; these were from anywhere in the world and published any time after 1 January 2020 until the end of 2022. From 26 720 titles and abstracts, 1181 were reviewed as full text, and 25 met our inclusion criteria. These 25 studies included one randomized control trial (RCT) and the remaining 24 analysed empirical data and made some attempt to control for confounding. Studies included were categorized by the type of intervention: contact tracing (seven studies); specific testing strategies (12 studies); strategies for isolating cases/contacts (four studies); and 'test, trace, isolate' (TTI) as a part of a package of interventions (two studies). None of the 25 studies were rated at low risk of bias and many were rated as serious risk of bias, particularly due to the likely presence of uncontrolled confounding factors, which was a major challenge in assessing the independent effects of TTI in observational studies. These confounding factors are to be expected from observational studies during an on-going pandemic, when the emphasis was on reducing the epidemic burden rather than trial design. Findings from these 25 studies suggested an important public health role for testing followed by isolation, especially where mass and serial testing was used to reduce transmission. Some of the most compelling analyses came from examining fine-grained within-country data on contact tracing; while broader studies which compared behaviour between countries also often found TTI led to reduced transmission and mortality, this was not universal. There was limited evidence for the benefit of isolation of cases/contacts away from the home environment. One study, an RCT, showed that daily testing of contacts could be a viable strategy to replace lengthy quarantine of contacts. Based on the scarcity of robust empirical evidence, we were not able to draw any firm quantitative conclusions about the quantitative impact of TTI interventions in different epidemic contexts. While the majority of studies found that testing, tracing and isolation reduced transmission, evidence for the scale of this impact is only available for specific scenarios and hence is not necessarily generalizable. Our review therefore emphasizes the need to conduct robust experimental studies that help inform the likely quantitative impact of different TTI interventions on transmission and their optimal design. Work is needed to support such studies in the context of future emerging epidemics, along with assessments of the cost-effectiveness of TTI interventions, which was beyond the scope of this review but will be critical to decision-making. This article is part of the theme issue 'The effectiveness of non-pharmaceutical interventions on the COVID-19 pandemic: the evidence'.

Comparing SARS-CoV-2 testing positivity rates and COVID-19 impact among different isolation strategies: a rapid systematic review and a modelling study

Background

The optimal isolation duration for patients with COVID-19 remains unclear. To support an update of World Health Organization (WHO)'s Living Clinical management guidelines for COVID-19 (https://www.who.int/publications/i/item/WHO-2019-nCoV-clinical-2022.2), this rapid systematic review and modelling study addresses the effects of different isolation periods for preventing onward transmission leading to hospitalisation and death among secondary cases.

Methods

We searched the WHO COVID-19 database for studies up to Feb 27, 2023. We included clinical studies of any design with COVID-19 patients confirmed by PCR test or rapid antigen test addressing the impact of any isolation strategy on preventing the spread of COVID-19. There were no restrictions on publication language, publication status, age of patients, severity of COVID-19, variants of SARS-COV-2, comorbidity of patients, isolation location, or co-interventions. We performed random-effects meta-analyses to summarise testing rates of persistent test positivity rates after COVID-19 infection. We performed pre-specified subgroup analyses by symptom status and meta-regression analyses for the proportion of fully vaccinated patients. We developed a model to compare the effects of three isolation strategies on onward transmission leading to hospitalisation and death. The three isolation strategies were (1) 5-day isolation, with no test to release; (2) removal of isolation based on a negative test; and (3) 10-day isolation, with no test to release. The model incorporates estimates of test positivity rates, effective reproduction number, isolation adherence, false negative rate, and hospitalisation rates or case fatality rates. To assess the impact of varying isolation adherence and false negative rates on rapid antigen testing, we conducted some sensitivity analyses. We used the Grading of Recommendations Assessment, Development and Evaluation approach to assess certainty of evidence. The protocol is registered with PROSPERO (CRD42022348626).

Findings

Fifteen studies addressing persistent test positivity rates including 4188 patients proved eligible. Asymptomatic patients (27.1%, 95% CI: 15.8%-40.0%) had a significantly lower rapid antigen test positive rate than symptomatic patients (68.1%, 95% CI: 40.6%-90.3%) on day 5. The rapid antigen test positive rate was 21.5% (95% CI: 0-64.1%; moderate certainty) on day 10. Our modelling study suggested that the risk difference (RD) for asymptomatic patients between 5-day isolation and 10-day isolation in hospitalisations (23 more hospitalisations of secondary cases per 10,000 patients isolated, 95% uncertainty interval (UI) 14 more to 33 more) and mortality (5 more per 10,000 patients, 95% UI 1 to 9 more) of secondary cases proved very small (very low certainty). For symptomatic patients, the potential impact of 5- versus 10-day isolation was much greater in hospitalisations (RD 186 more per 10,000 patients, 95% UI 113 more to 276 more; very low certainty) and mortality (RD 41 more per 10,000 patients, 95% UI 11 more to 73 more; very low certainty). There may be little or no difference between removing isolation based on a negative antigen test and 10-day isolation in the onward transmission leading to hospitalisation or death, but the average isolation period (mean difference -3 days) will be shorter for the removal of isolation based on a negative antigen test (moderate certainty).

Interpretation

5 days versus 10 days of isolation in asymptomatic patients may result in a small amount of onward transmission and negligible hospitalisation and mortality; however, in symptomatic patients, the level of onward transmission is concerning and may lead to high hospitalisation and death rates. The evidence is, however, very uncertain.

Funding

This work was done in collaboration with WHO.

SARS-CoV-2 Testing Strategies in the Diagnosis and Management of COVID-19 Patients in Low-Income Countries: A Scoping Review

The accuracy of diagnostic laboratory tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can impact downstream clinical procedures in managing and controlling the outbreak of coronavirus disease 2019 (COVID-19). To assess the effectiveness of laboratory tools for managing COVID-19 patients in low-income countries (LICs), we systematically searched the PubMed, Embase, Scopus and CINHAL databases for reports published between January 2020 and June 2022. We found that 22 of 1303 articles reported the performance of various SARS-CoV-2 detection tools across 10 LICs. These tools were (1) real-time reverse transcriptase polymerase chain reaction (RT-PCR); (2) reverse transcription loop-mediated isothermal amplification (RT-LAMP); (3) rapid diagnostic tests (RDTs); (4) enzyme-linked immunosorbent assay (ELISA); and (5) dot-blot immunoassay. The detection of COVID-19 is largely divided into two main streams-direct virus (antigen) detection and serology (immunoglobulin)-based detection. Point-of-care testing using antigen-based RDTs is preferred in LICs because of cost effectiveness and simplicity in the test procedures. The nucleic acid amplification technology (RT-PCR and RT-LAMP) has the highest diagnostic performance among the available tests, but it is not broadly used in this context due to costs and shortage of facilities/trained staff. The serology-based test method is affected by antibody interferences and varying amounts of SARS-CoV-2 immunoglobulins expressed at different stages of disease onset. We further discuss the effectiveness and shortcomings of each of these tools in the diagnosis and management of COVID-19. Using the LICs as the study model, our findings highlight ways to improve the quality and turnaround time of COVID-19 testing in resource-constrained settings, notably through local/international collaborative efforts to refine the molecular-based or immunoassay-based testing technologies.

Nonpharmaceutical interventions for managing SARS-CoV-2

PURPOSE OF REVIEW

Initial response strategies to the COVID-19 pandemic were heavily reliant on nonpharmaceutical interventions (NPIs), a set of measures implemented to slow or even stop the spread of infection. Here, we reviewed key measures used during the COVID-19 pandemic.

RECENT FINDINGS

Some NPIs were successful in reducing the transmission of SARS-CoV-2. Personal protective measures such as face masks were widely used, and likely had some effect on transmission. The development and production of rapid antigen tests allowed self-diagnosis in the community, informing isolation and quarantine measures. Community-wide measures such as school closures, workplace closures and complete stay-at-home orders were able to reduce contacts and prevent transmission. They were widely used in the pandemic and contributed to reduce transmission in the community; however, there were also negative unintended consequences in the society and economy.

SUMMARY

NPIs slowed the spread of SARS-CoV-2 and are essential for pandemic preparedness and response. Understanding which measures are more effective at reducing transmission with lower costs is imperative.

An overview of the most important preanalytical factors influencing the clinical performance of SARS-CoV-2 antigen rapid diagnostic tests (Ag-RDTs)

Due to the many technical limitations of molecular biology, the possibility to sustain enormous volumes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnostic testing relies strongly on the use of antigen rapid diagnostic tests (Ag-RDTs). Besides a limited analytical sensitivity, the manually intensive test procedures needed for performing these tests, very often performed by unskilled personnel or by the patients themselves, may contribute to considerably impair their diagnostic accuracy. We provide here an updated overview on the leading preanalytical drawbacks that may impair SARS-CoV-2 Ag-RDT accuracy, and which encompass lower diagnostic sensitivity in certain age groups, in asymptomatic subjects and those with a longer time from symptoms onset, in vaccine recipients, in individuals not appropriately trained to their usage, in those recently using oral or nasal virucidal agents, in oropharyngeal swabs and saliva, as well as in circumstances when instructions provided by the manufacturers are unclear, incomplete or scarcely readable and intelligible. Acknowledging these important preanalytical limitations will lead the way to a better, more clinically efficient and even safer use of this important technology, which represents an extremely valuable resource for management of the ongoing pandemic.