Effectiveness of rapid antigen testing for screening of asymptomatic individuals to limit the transmission of SARS-CoV-2: A rapid review.

Rapid antigen detection tests (RADTs) offer advantages over gold-standard reverse transcription polymerase chain reaction (RT-PCR) tests in that they are cheaper and provide faster results, thus enabling prompt isolation of positive SARS-CoV-2 cases and quarantine of close contacts. The aim of this study was to collate and synthesise empirical evidence on the effectiveness of rapid antigen testing for the screening (including serial testing) and surveillance of asymptomatic individuals to limit the transmission of SARS-CoV-2. A rapid review was undertaken in MEDLINE (EBSCO), EMBASE (OVID), Cochrane Library, Europe PMC and Google Scholar up until 19 July 2021, supplemented by a grey literature search. Of the identified 1222 records, 19 reports referring to 16 studies were included. Eight included studies examined the effectiveness of RADTs for population-level screening, four for pre-event screening and four for serial testing (schools, a prison, a university sports programme and in care homes). Overall, there is uncertainty regarding the effectiveness of rapid antigen testing for the screening of asymptomatic individuals to limit the transmission of SARS-CoV-2. This uncertainty is due to the inconsistent results, the relatively low number of studies identified, the predominantly observational and/or uncontrolled nature of the study designs used, and concerns regarding methodological quality. Given this uncertainty, more real-world research evidence in relevant settings, which is of good quality and timely, as well as economic evaluation, is required to inform public policy on the widespread use of RADTs in asymptomatic individuals.

Transmission of SARS-CoV-2 by children: a rapid review, 30 December 2019 to 10 August 2020.

BackgroundThe role of children in the transmission of SARS-CoV-2 during the early pandemic was unclear.AimWe aimed to review studies on the transmission of SARS-CoV-2 by children during the early pandemic.MethodsWe searched MEDLINE, Embase, the Cochrane Library, Europe PubMed Central and the preprint servers medRxiv and bioRxiv from 30 December 2019 to 10 August 2020. We assessed the quality of included studies using a series of questions adapted from related tools. We provide a narrative synthesis of the results.ResultsWe identified 28 studies from 17 countries. Ten of 19 studies on household and close contact transmission reported low rates of child-to-adult or child-to-child transmission. Six studies investigated transmission of SARS-CoV-2 in educational settings, with three studies reporting 183 cases from 14,003 close contacts who may have contracted COVID-19 from children index cases at their schools. Three mathematical modelling studies estimated that children were less likely to infect others than adults. All studies were of low to moderate quality.ConclusionsDuring the early pandemic, it appeared that children were not substantially contributing to household transmission of SARS-CoV-2. School-based studies indicated that transmission rates in this setting were low. Large-scale studies of transmission chains using data collected from contact tracing and serological studies detecting past evidence of infection would be needed to verify our findings.

Pharmacological interventions to prevent Covid-19 disease: A rapid review.

The aim of this rapid review was to determine the effectiveness of pharmacological interventions (excluding vaccines) to prevent coronavirus disease 2019 (Covid-19) or reduce the severity of disease. A systematic search of published peer-reviewed articles and non-peer-reviewed pre-prints was undertaken from 1 January 2020 to 17 August 2021. Four randomised controlled trials (RCTs) and one non-RCT were included; three trials (two RCTs and one non-RCT) tested ivermectin with or without carrageenan. While all reported some potential protective effect of ivermectin, these trials had a high risk of bias and the certainty of evidence was deemed to be 'very low'. One RCT tested bamlanivimab compared to placebo and reported a significantly reduced incidence of Covid-19 in the intervention group; this trial had a low risk of bias however the certainty of evidence was deemed 'very low'. The fifth RCT tested casirivimab plus imdevimab versus placebo and reported that the combination of monoclonal antibodies significantly reduced the incidence of symptomatic and asymptomatic SARS-CoV-2 infection, viral load, duration of symptomatic disease and the duration of a high viral load; this trial was deemed to have a low risk of bias, and the certainty of evidence was 'low'. The designations 'low' and 'very low' regarding the certainty of evidence indicate that the estimate of effect is uncertain and therefore is unsuitable for informing decision-making. At the time of writing, there is insufficient high quality evidence to support the use of pharmacological interventions to prevent Covid-19.

Effectiveness of public health measures to prevent the transmission of SARS-CoV-2 at mass gatherings: A rapid review.

Mass gatherings play an important role in society, but since the onset of the Covid-19 pandemic, they have generally been restricted in order to mitigate transmission of SARS-CoV-2. The aim of this study was to summarise the evidence regarding the effectiveness of public health measures at preventing the transmission of SARS-CoV-2 at mass gatherings, and hence inform guidance on the organisation of these events. A rapid review was undertaken in Cochrane, Embase (OVID), Medline (OVID), Google, Web of Science and Europe PMC from 1 January 2020 to 3 June 2021. Of the identified 1,624 citations, 14 articles referring to 11 unique studies were included. This rapid review found evidence from 11 studies (involving approximately 30,482 participants) that implementing a range of measures may reduce the risk of SARS-CoV-2 transmission at mass gatherings; however, it is unlikely that this risk can be eliminated entirely. All studies adopted a layered mitigation approach involving multiple measures, which may be more effective than relying on any single measure. The number and intensity of measures implemented varied across studies, with most implementing resource intense measures. Importantly, all included studies were only of 'fair' to 'poor' quality. In conclusion, there is currently limited evidence on the effectiveness of measures to prevent SARS-CoV-2 transmission at mass gatherings. As mass gatherings recommence, continued adoption of known mitigation measures is required to limit the risk of transmission, as well as ongoing research and surveillance to monitor the potential impact of these events on the wider population and healthcare system.

Airborne transmission of SARS-CoV-2 via aerosols.

A key consideration in the Covid-19 pandemic is the dominant modes of transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. The objective of this review was to synthesise the evidence for the potential airborne transmission of SARS-CoV-2 via aerosols. Systematic literature searches were conducted in PubMed, Embase, Europe PMC and National Health Service UK evidence up to 27 July 2020. A protocol was published and Cochrane guidance for rapid review methodology was adhered to throughout. Twenty-eight studies were identified. Seven out of eight epidemiological studies suggest aerosol transmission may occur, with enclosed environments and poor ventilation noted as possible contextual factors. Ten of the 16 air sampling studies detected SARS-CoV-2 ribonucleic acid; however, only three of these studies attempted to culture the virus with one being successful in a limited number of samples. Two of four virological studies using artificially generated aerosols indicated that SARS-CoV-2 is viable in aerosols. The results of this review indicate there is inconclusive evidence regarding the viability and infectivity of SARS-CoV-2 in aerosols. Epidemiological studies suggest possible transmission, with contextual factors noted. Viral particles have been detected in air sampling studies with some evidence of clinical infectivity, and virological studies indicate these particles may represent live virus, adding further plausibility. However, there is uncertainty as to the nature and impact of aerosol transmission of SARS-CoV-2, and its relative contribution to the Covid-19 pandemic compared with other modes of transmission.

Alternative clinical specimens for the detection of SARS-CoV-2: A rapid review.

The collection of nasopharyngeal swabs to test for the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an invasive technique with implications for patients and clinicians. Alternative clinical specimens from the upper respiratory tract may offer benefits in terms of collection, comfort and infection risk. The objective of this review was to synthesise the evidence for detection of SARS-CoV-2 ribonucleic acid (RNA) using reverse transcription polymerase chain reaction (RT-PCR) tested saliva or nasal specimens compared with RT-PCR tested nasopharyngeal specimens. Searches were conducted in PubMed, Embase, Europe PMC and NHS evidence from December 2019 to 20 July 2020. Eighteen studies were identified; 12 for saliva, four for nasal and two included both specimen types. For saliva-based studies, the proportion of saliva samples testing positive relative to all positive samples in each study ranged from 82.9% to 100%; detection in nasopharyngeal specimens ranged from 76.7% to 100%; positive agreement between specimens for overall detection ranged from 65.4% to 100%. For nasal-based studies, the proportion of nasal swabs testing positive relative to all positive samples in each study ranged from 81.9% to 100%; detection in nasopharyngeal specimens ranged from 70% to 100%; positive agreement between specimens for overall detection ranged from 62.3% to 100%. The results indicate an inconsistency in the detection of SARS-CoV-2 RNA in the specimen types included, often with neither the index nor the reference of interest detecting all known cases. Depending on the test environment, these clinical specimens may offer a viable alternative to standard. However, at present the evidence is limited, of variable quality, and relatively inconsistent.

The duration of infectiousness of individuals infected with SARS-CoV-2.

OBJECTIVES: To summarise the evidence on the duration of infectiousness of individuals in whom SARS-CoV-2 ribonucleic acid is detected. METHODS: A rapid review was undertaken in PubMed, Europe PubMed Central and EMBASE from 1 January 2020 to 26 August 2020. RESULTS: We identified 15 relevant studies, including 13 virus culture and 2 contact tracing studies. For 5 virus culture studies, the last day on which SARS-CoV-2 was isolated occurred within 10 days of symptom onset. For another 5 studies, SARS-CoV-2 was isolated beyond day 10 for approximately 3% of included patients. The remaining 3 virus culture studies included patients with severe or critical disease; SARS-CoV-2 was isolated up to day 32 in one study. Two studies identified immunocompromised patients from whom SARS-CoV-2 was isolated for up to 20 days. Both contact tracing studies, when close contacts were first exposed greater than 5 days after symptom onset in the index case, found no evidence of laboratory-confirmed onward transmission of SARS-CoV-2. CONCLUSION: COVID-19 patients with mild-to-moderate illness are highly unlikely to be infectious beyond 10 days of symptoms. However, evidence from a limited number of studies indicates that patients with severe-to-critical illness or who are immunocompromised, may shed infectious virus for longer.

Immune response following infection with SARS-CoV-2 and other coronaviruses: A rapid review.

In this review, we systematically searched and summarized the evidence on the immune response and reinfection rate following SARS-CoV-2 infection. We also retrieved studies on SARS-CoV and MERS-CoV to assess the long-term duration of antibody responses. A protocol based on Cochrane rapid review methodology was adhered to and databases were searched from 1/1/2000 until 26/5/2020. Of 4744 citations retrieved, 102 studies met our inclusion criteria. Seventy-four studies were retrieved on SARS-CoV-2. While the rate and timing of IgM and IgG seroconversion were inconsistent across studies, most seroconverted for IgG within 2 weeks and 100% (N = 62) within 4 weeks. IgG was still detected at the end of follow-up (49-65 days) in all patients (N = 24). Neutralizing antibodies were detected in 92%-100% of patients (up to 53 days). It is not clear if reinfection with SARS-CoV-2 is possible, with studies more suggestive of intermittent detection of residual RNA. Twenty-five studies were retrieved on SARS-CoV. In general, SARS-CoV-specific IgG was maintained for 1-2 years post-infection and declined thereafter, although one study detected IgG up to 12 years post-infection. Neutralizing antibodies were detected up to 17 years in another study. Three studies on MERS-CoV reported that IgG may be detected up to 2 years. In conclusion, limited early data suggest that most patients seroconvert for SARS-CoV-2-specific IgG within 2 weeks. While the long-term duration of antibody responses is unknown, evidence from SARS-CoV studies suggest SARS-CoV-specific IgG is sustained for 1-2 years and declines thereafter.

Inferred duration of infectious period of SARS-CoV-2: rapid scoping review and analysis of available evidence for asymptomatic and symptomatic COVID-19 cases.

OBJECTIVES: Our objective was to review the literature on the inferred duration of the infectious period of COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, and provide an overview of the variation depending on the methodological approach. DESIGN: Rapid scoping review. Literature review with fixed search terms, up to 1 April 2020. Central tendency and variation of the parameter estimates for infectious period in (A) asymptomatic and (B) symptomatic cases from (1) virological studies (repeated testing), (2) tracing studies and (3) modelling studies were gathered. Narrative review of viral dynamics. INFORMATION SOURCES: Search strategies developed and the following searched: PubMed, Google Scholar, MedRxiv and BioRxiv. Additionally, the Health Information Quality Authority (Ireland) viral load synthesis was used, which screened literature from PubMed, Embase, ScienceDirect, NHS evidence, Cochrane, medRxiv and bioRxiv, and HRB open databases. RESULTS: There was substantial variation in the estimates, and how infectious period was inferred. One study provided approximate median infectious period for asymptomatic cases of 6.5-9.5 days. Median presymptomatic infectious period across studies varied over <1-4 days. Estimated mean time from symptom onset to two negative RT-PCR tests was 13.4 days (95% CI 10.9 to 15.8) but was shorter when studies included children or less severe cases. Estimated mean duration from symptom onset to hospital discharge or death (potential maximal infectious period) was 18.1 days (95% CI 15.1 to 21.0); time to discharge was on average 4 days shorter than time to death. Viral dynamic data and model infectious parameters were often shorter than repeated diagnostic data. CONCLUSIONS: There are limitations of inferring infectiousness from repeated diagnosis, viral loads and viral replication data alone and also potential patient recall bias relevant to estimating exposure and symptom onset times. Despite this, available data provide a preliminary evidence base to inform models of central tendency for key parameters and variation for exploring parameter space and sensitivity analysis.

SARS-CoV-2 detection, viral load and infectivity over the course of an infection.

OBJECTIVES: To summarise the evidence on the detection pattern and viral load of SARS-CoV-2 over the course of an infection (including any asymptomatic or pre-symptomatic phase), and the duration of infectivity. METHODS: A systematic literature search was undertaken in PubMed, Europe PubMed Central and EMBASE from 30 December 2019 to 12 May 2020. RESULTS: We identified 113 studies conducted in 17 countries. The evidence from upper respiratory tract samples suggests that the viral load of SARS-CoV-2 peaks around symptom onset or a few days thereafter, and becomes undetectable about two weeks after symptom onset; however, viral loads from sputum samples may be higher, peak later and persist for longer. There is evidence of prolonged virus detection in stool samples, with unclear clinical significance. No study was found that definitively measured the duration of infectivity; however, patients may not be infectious for the entire duration of virus detection, as the presence of viral ribonucleic acid may not represent transmissible live virus. CONCLUSION: There is a relatively consistent trajectory of SARS-CoV-2 viral load over the course of COVID-19 from respiratory tract samples, however the duration of infectivity remains uncertain.