SARS-CoV-2 antibody responses associate with sex, age and disease severity in previously uninfected people admitted to hospital with COVID-19: An ISARIC4C prospective study.

The SARS-CoV-2 pandemic enables the analysis of immune responses induced against a novel coronavirus infecting immunologically naïve individuals. This provides an opportunity for analysis of immune responses and associations with age, sex and disease severity. Here we measured an array of solid-phase binding antibody and viral neutralising Ab (nAb) responses in participants (n=337) of the ISARIC4C cohort and characterised their correlation with peak disease severity during acute infection and early convalescence. Overall, the responses in a Double Antigen Binding Assay (DABA) for antibody to the receptor binding domain (anti-RBD) correlated well with IgM as well as IgG responses against viral spike, S1 and nucleocapsid protein (NP) antigens. DABA reactivity also correlated with nAb. As we and others reported previously, there is greater risk of severe disease and death in older men, whilst the sex ratio was found to be equal within each severity grouping in younger people. In older males with severe disease (mean age 68 years), peak antibody levels were found to be delayed by one to two weeks compared with women, and nAb responses were delayed further. Additionally, we demonstrated that solid-phase binding antibody responses reached higher levels in males as measured via DABA and IgM binding against Spike, NP and S1 antigens. In contrast, this was not observed for nAb responses. When measuring SARS-CoV-2 RNA transcripts (as a surrogate for viral shedding) in nasal swabs at recruitment, we saw no significant differences by sex or disease severity status. However, we have shown higher antibody levels associated with low nasal viral RNA indicating a role of antibody responses in controlling viral replication and shedding in the upper airway. In this study, we have shown discernible differences in the humoral immune responses between males and females and these differences associate with age as well as with resultant disease severity.

National and regional prevalence of SARS-CoV-2 antibodies in primary and secondary school children in England: the School Infection Survey, a national open cohort study, November 2021SARS-CoV-2 antibody prevalence in school children.

BACKGROUND: SARS-CoV-2 infection rates are likely to be underestimated in children because of asymptomatic or mild infections. We aim to estimate national and regional prevalence of SARS-CoV-2 antibodies in primary (4-11 years old) and secondary (11-18 years old) school children between 10 November and 10 December 2021. METHODS: Cross-sectional surveillance in England using two-stage sampling, firstly stratifying into regions and selecting local authorities, then selecting schools according to a stratified sample within selected local authorities. Participants were sampled using a novel oral fluid-validated assay for SARS-CoV-2 spike and nucleocapsid IgG antibodies. RESULTS: 4980 students from 117 state-funded schools (2706 from 83 primary schools, 2274 from 34 secondary schools) provided a valid sample. After weighting for age, sex, and ethnicity, and adjusting for assay accuracy, the national prevalence of SARS-CoV-2 antibodies in primary school students, who were all unvaccinated, was 40.1% (95% CI 37.3-43.0). Antibody prevalence increased with age (p < 0.001) and was higher in urban than rural schools (p = 0.01). In secondary school students, the adjusted, weighted national prevalence of SARS-CoV-2 antibodies was 82.4% (95% CI 79.5-85.1); including 71.5% (95% CI 65.7-76.8) in unvaccinated and 97.5% (95% CI 96.1-98.5) in vaccinated students. Antibody prevalence increased with age (p < 0.001), and was not significantly different in urban versus rural students (p = 0.1). CONCLUSIONS: In November 2021, using a validated oral fluid assay, national SARS-CoV-2 seroprevalence was estimated to be 40.1% in primary school students and 82.4% in secondary school students. In unvaccinated children, this was approximately threefold higher than confirmed infections highlighting the importance of seroprevalence studies to estimate prior exposure. DATA AVAILABILITY: Deidentified study data are available for access by accredited researchers in the ONS Secure Research Service (SRS) for accredited research purposes under part 5, chapter 5 of the Digital Economy Act 2017. For further information about accreditation, contact Research.support@ons.gov.uk or visit the SRS website.

Secondary attack rates in primary and secondary school bubbles following a confirmed case: Active, prospective national surveillance, November to December 2020, England.

BACKGROUND: Following the full re-opening of schools in England and emergence of the SARS-CoV-2 Alpha variant, we investigated the risk of SARS-CoV-2 infection in students and staff who were contacts of a confirmed case in a school bubble (school groupings with limited interactions), along with their household members. METHODS: Primary and secondary school bubbles were recruited into sKIDsBUBBLE after being sent home to self-isolate following a confirmed case of COVID-19 in the bubble. Bubble participants and their household members were sent home-testing kits comprising nasal swabs for RT-PCR testing and whole genome sequencing, and oral fluid swabs for SARS-CoV-2 antibodies. RESULTS: During November-December 2020, 14 bubbles were recruited from 7 schools, including 269 bubble contacts (248 students, 21 staff) and 823 household contacts (524 adults, 299 children). The secondary attack rate was 10.0% (6/60) in primary and 3.9% (4/102) in secondary school students, compared to 6.3% (1/16) and 0% (0/1) among staff, respectively. The incidence rate for household contacts of primary school students was 6.6% (12/183) and 3.7% (1/27) for household contacts of primary school staff. In secondary schools, this was 3.5% (11/317) and 0% (0/1), respectively. Household contacts were more likely to test positive if their bubble contact tested positive although there were new infections among household contacts of uninfected bubble contacts. INTERPRETATION: Compared to other institutional settings, the overall risk of secondary infection in school bubbles and their household contacts was low. Our findings are important for developing evidence-based infection prevention guidelines for educational settings.

Epidemiology of SARS-CoV-2 infection among staff and students in a cohort of English primary and secondary schools during 2020-2021.

Background: There remains uncertainty about the epidemiology of SARS-CoV-2 among school students and staff and the extent to which non-pharmaceutical-interventions reduce the risk of school settings. Methods: We conducted an open cohort study in a sample of 59 primary and 97 secondary schools in 15 English local authority areas that were implementing government guidance to schools open during the pandemic. We estimated SARS-CoV-2 infection prevalence among those attending school, antibody prevalence, and antibody negative to positive conversion rates in staff and students over the school year (November 2020-July 2021). Findings: 22,585 staff and students participated. SARS-CoV-2 infection prevalence among those attending school was highest during the first two rounds of testing in the autumn term, ranging from 0.7% (95% CI 0.2, 1.2) among primary staff in November 2020 to 1.6% (95% CI 0.9, 2.3) among secondary staff in December 2020. Antibody conversion rates were highest in the autumn term. Infection patterns were similar between staff and students, and between primary and secondary schools. The prevalence of nucleoprotein antibodies increased over the year and was lower among students than staff. SARS-CoV-2 infection prevalence in the North-West region was lower among secondary students attending school on normal school days than the regional estimate for secondary school-age children. Interpretation: SARS-CoV-2 infection prevalence in staff and students attending school varied with local community infection rates. Non-pharmaceutical interventions intended to prevent infected individuals attending school may have partially reduced the prevalence of infection among those on the school site. Funding: UK Department of Health and Social Care.

The COVID-19 Schools Infection Survey in England: Protocol and Participation Profile for a Prospective Observational Cohort Study.

BACKGROUND: One of the most debated questions in the COVID-19 pandemic has been the role of schools in SARS-CoV-2 transmission. The COVID-19 Schools Infection Survey (SIS) aims to provide much-needed evidence addressing this issue. OBJECTIVE: We present the study protocol and participation profile for the SIS study, aimed at assessing the role of schools in SARS-CoV-2 infection and transmission within school settings, and investigating how transmission within and from schools could be mitigated through the implementation of school COVID-19 control measures. METHODS: SIS was a multisite, prospective, observational cohort study conducted in a stratified random sample of primary and secondary schools in selected local authorities in England. A total of 6 biobehavioral surveys were planned among participating students and staff during the 2020-2021 academic year, between November 2020 and July 2021. Key measurements were SARS-CoV-2 virus prevalence, assessed by nasal swab polymerase chain reaction; anti-SARS-CoV-2 (nucleocapsid protein) antibody prevalence and conversion, assessed in finger-prick blood for staff and oral fluid for students; student and staff school attendance rates; feasibility and acceptability of school-level implementation of SARS-CoV-2 control measures; and investigation of selected school outbreaks. The study was approved by the United Kingdom Health Security Agency Research Support and Governance Office (NR0237) and London School of Hygiene & Tropical Medicine Ethics Review Committee (reference 22657). RESULTS: Data collection and laboratory analyses were completed by September 2021. A total of 22,585 individuals-1891 staff and 4654 students from 59 primary schools and 5852 staff and 10,188 students from 97 secondary schools-participated in at least one survey. Across all survey rounds, staff and student participation rates were 45.2% and 16.4%, respectively, in primary schools and 30% and 15.2%, respectively, in secondary schools. Although primary student participation increased over time, and secondary student participation remained reasonably consistent, staff participation declined across rounds, especially for secondary school staff (3165/7583, 41.7% in round 1 and 2290/10,374, 22.1% in round 6). Although staff participation overall was generally reflective of the eligible staff population, student participation was higher in schools with low absenteeism, a lower proportion of students eligible for free school meals, and from schools in the least deprived locations (in primary schools, 446/4654, 9.6% of participating students were from schools in the least deprived quintile compared with 1262/22,225, 5.7% of eligible students). CONCLUSIONS: We outline the study design, methods, and participation, and reflect on the strengths of the SIS study as well as the practical challenges encountered and the strategies implemented to address these challenges. The SIS study, by measuring current and incident infection over time, alongside the implementation of control measures in schools across a range of settings in England, aims to inform national guidance and public health policy for educational settings. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR1-10.2196/34075.

Prevalence of hepatitis B immunity and infection in home self-sampling HIV service users.

OBJECTIVES: Although hepatitis B virus (HBV) vaccination for high-risk groups including gay, bisexual and other men who have sex with men (MSM) is recommended in the UK, data on HBV immunisation coverage are limited. This study aimed to understand the prevalence of HBV infection, susceptibility and immunity due to immunisation among a high-risk population of MSM and heterosexuals who are less likely to attend sexual health services. METHODS: Residual HIV-negative serology samples archived from a national HIV self-sampling service in 2016 were tested for HBV markers using an unlinked anonymous approach. Prevalence of HBV infection, evidence of immunisation and susceptibility were calculated and stratified by individuals' characteristics. Multinomial logistic regression was used to estimate relative risk ratios (RRRs) associated with covariates. RESULTS: Of 2172 samples tested, 1497 (68.9%) were from MSM and 657 (30.2%) were from heterosexuals. Susceptibility to HBV infection was 66.1% among MSM and 77.0% among heterosexuals. Only 29.9% of MSM and 17.4% of heterosexuals had serological evidence of immunisation. Current infection was 1.1% in heterosexuals and 0.2% in MSM. Adjusted analysis showed evidence of immunisation was lower among heterosexuals (RRR 0.66, 95% CI 0.50 to 0.86) and those with no previous HIV test (RRR 0.41, 95% CI 0.31 to 0.54), and higher in those of other white or other ethnicity. CONCLUSIONS: Among MSM and heterosexual users of a self-sampling HIV service, evidence of immunisation to HBV infection was low and susceptibility to infection was comparatively high, suggesting suboptimal delivery of HBV immunisation in sexual health services.

Simple, sensitive, specific self-sampling assay secures SARS-CoV-2 antibody signals in sero-prevalence and post-vaccine studies.

At-home sampling is key to large scale seroprevalence studies. Dried blood spot (DBS) self-sampling removes the need for medical personnel for specimen collection but facilitates specimen referral to an appropriately accredited laboratory for accurate sample analysis. To establish a highly sensitive and specific antibody assay that would facilitate self-sampling for prevalence and vaccine-response studies. Paired sera and DBS eluates collected from 439 sero-positive, 382 sero-negative individuals and DBS from 34 vaccine recipients were assayed by capture ELISAs for IgG and IgM antibody to SARS-CoV-2. IgG and IgM combined on DBS eluates achieved a diagnostic sensitivity of 97.9% (95%CI 96.6 to 99.3) and a specificity of 99.2% (95% CI 98.4 to 100) compared to serum, displaying limits of detection equivalent to 23 and 10 WHO IU/ml, respectively. A strong correlation (r = 0.81) was observed between serum and DBS reactivities. Reactivity remained stable with samples deliberately rendered inadequate, (p = 0.234) and when samples were accidentally damaged or 'invalid'. All vaccine recipients were sero-positive. This assay provides a secure method for self-sampling by DBS with a sensitivity comparable to serum. The feasibility of DBS testing in sero-prevalence studies and in monitoring post-vaccine responses was confirmed, offering a robust and reliable tool for serological monitoring at a population level.

Nosocomial transmission of hepatitis E virus and development of chronic infection: The wider impact of COVID-19.

BACKGROUND: Transmission of hepatitis E virus (HEV) within the healthcare setting is extremely rare. Additionally, the development of chronic HEV infection in association with severe acute respiratory syndrome coronavirus disease 2 (SARS-CoV-2) infection and/or its immunomodulatory therapy has not been reported previously. AIMS: To describe the investigation and management of a nosocomial HEV transmission incident during the coronavirus disease 2019 (COVID-19) pandemic. METHODS: Epidemiological and molecular investigation of two individuals hospitalised with COVID-19 who were both diagnosed with HEV infection. RESULTS: Findings from our investigation were consistent with transmission of HEV from one patient with a community-acquired HEV infection to another individual (identical HEV sequences were identified in the two patients), most likely due to a breach in infection control practices whilst both patients shared a bed space on the intensive care unit (ICU). Chronic HEV infection requiring treatment with ribavirin developed in one patient with prolonged lymphopaenia attributable to COVID-19 and/or the immunomodulators received for its treatment. Further investigation did not identify transmission of HEV to any other patients or to healthcare workers. CONCLUSIONS: The extraordinary demands that the COVID-19 pandemic has placed on all aspects of healthcare, particularly within ICU settings, has greatly challenged the ability to consistently maintain optimal infection prevention and control practices. Under the significant pressures of the COVID-19 pandemic a highly unusual nosocomial HEV transmission incident occurred complicated further by progression to a chronic HEV infection in one patient.

SARS Antibody Testing in Children: Development of Oral Fluid Assays for IgG Measurements.

Seroepidemiological studies to monitor antibody kinetics are important for assessing the extent and spread of SARS-CoV-2 in a population. Noninvasive sampling methods are advantageous for reducing the need for venipuncture, which may be a barrier to investigations, particularly in pediatric populations. Oral fluids are obtained by gingiva-crevicular sampling from children and adults and are very well accepted. Enzyme immunoassays (EIAs) based on these samples have acceptable sensitivity and specificity compared to conventional serum-based antibody EIAs and are suitable for population-based surveillance. We describe the development and evaluation of SARS-CoV-2 IgG EIAs using SARS-CoV-2 viral nucleoprotein (NP) and spike (S) proteins in IgG isotype capture format and an indirect receptor-binding-domain (RBD) IgG EIA, intended for use in children as a primary endpoint. All three assays were assessed using a panel of 1,999 paired serum and oral fluids from children and adults participating in school SARS-CoV-2 surveillance studies during and after the first and second pandemic wave in the United Kingdom. The anti-NP IgG capture assay was the best candidate, with an overall sensitivity of 75% (95% confidence interval [CI]: 71 to 79%) and specificity of 99% (95% CI: 78 to 99%) compared with paired serum antibodies. Sensitivity observed in children (80%, 95% CI: 71 to 88%) was higher than that in adults (67%, CI: 60% to 74%). Oral fluid assays (OF) using spike protein and RBD antigens were also 99% specific and achieved reasonable but lower sensitivity in the target population (78%, 95% CI [68% to 86%] and 53%, 95% CI [43% to 64%], respectively). IMPORTANCE We report on the first large-scale assessment of the suitability of oral fluids for detection of SARS-CoV-2 antibody obtained from healthy children attending school. The sample type (gingiva-crevicular fluid, which is a transudate of blood but is not saliva) can be self collected. Although detection of antibodies in oral fluids is less sensitive than that in blood, our study suggests an optimal format for operational use. The laboratory methods we have developed can reliably measure antibodies in children, who are able to take their own samples. Our findings are of immediate practical relevance for use in large-scale seroprevalence studies designed to measure exposure to infection, as they typically require venipuncture. Overall, our data indicate that OF assays based on the detection of SARS-CoV-2 antibodies are a tool suitable for population-based seroepidemiology studies in children and highly acceptable in children and adults, as venipuncture is no longer necessary.

Transmission of SARS-CoV-2 in the household setting: A prospective cohort study in children and adults in England.

OBJECTIVES: To measure secondary attack rates (SARs) in prospectively followed household contacts of paediatric and adult cases of SARS-CoV-2 infection in England. METHODS: Self-taken nasal swabs from household contacts of PCR confirmed cases of COVID-19  and blood samples  on day 35 were tested for evidence of infection with SARS-CoV-2 virus. RESULTS: The secondary attack rate (SAR) among 431 contacts of 172 symptomatic index cases  was 33% (95% confidence intervals [CI] 25-40) and was lower from primary cases without respiratory symptoms, 6% (CI 0-14) vs 37% (CI 29-45), p = 0.030. The SAR from index cases <11 years  was  25% (CI 12-38). SARs ranged from 16% (4-28) in contacts <11 years old to 36% (CI 28-45) in contacts aged 19-54 years (p = 0.119). The proportion infected who developed symptoms (78%) was similar by age (p = 0.44) though <19 year olds had fewer mean number of symptoms than adults (p = 0.001) and fewer reported loss of sense of taste or smell (p = 0.0001). CONCLUSIONS: There are high risks of  transmission of SARS-CoV-2 virus in the home, including those where infection is introduced by a child. The risk of children acquiring infection was lower than that in adults and fewer developed typical symptoms of Covid-19 infection.

Severe Acute Respiratory Syndrome Coronavirus-2 Infections in Critical Care Staff: Beware the Risks Beyond the Bedside.

OBJECTIVES: Critical care workers were considered to be at high risk of severe acute respiratory syndrome coronavirus-2 infection from patients during the first wave of the pandemic. Staff symptoms, previous swab testing, and antibody prevalence were correlated with patient admissions to investigate this assumption. DESIGN: Cross-sectional study. SETTING: A large critical care department in a tertiary-care teaching hospital in London, United Kingdom. SUBJECTS: Staff working in critical care. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Participants completed a questionnaire and provided a serum sample for severe acute respiratory syndrome coronavirus-2 antibody testing over a 3-day period in April 2020. We compared the timing of symptoms in staff to the coronavirus disease 2019 patient admissions to critical care. We also identified factors associated with antibody detection. Of 625 staff 384 (61.4%) reported previous symptoms and 124 (19.8%) had sent a swab for testing. Severe acute respiratory syndrome coronavirus-2 infection had been confirmed in 37 of those swabbed (29.8%). Overall, 21% (131/625) had detectable severe acute respiratory syndrome coronavirus-2 antibody, of whom 9.9% (13/131) had been asymptomatic. The peak onset of symptoms among staff occurred 2 weeks before the peak in coronavirus disease 2019 patient admissions. Staff who worked in multiple departments across the hospital were more likely to be seropositive. Staff with a symptomatic household contact were also more likely to be seropositive at 31.3%, compared with 16.2% in those without (p < 0.0001). CONCLUSIONS: Staff who developed coronavirus disease 2019 were less likely to have caught it from their patients in critical care. Other staff, other areas of the hospital, and the wider community are more likely sources of infection. These findings indicate that personal protective equipment was effective at preventing transmission from patients. However, staff also need to maintain protective measures away from the bedside.

SARS-CoV-2 RNA detected in blood products from patients with COVID-19 is not associated with infectious virus.

Background: Laboratory diagnosis of SARS-CoV-2 infection (the cause of COVID-19) uses PCR to detect viral RNA (vRNA) in respiratory samples. SARS-CoV-2 RNA has also been detected in other sample types, but there is limited understanding of the clinical or laboratory significance of its detection in blood. Methods: We undertook a systematic literature review to assimilate the evidence for the frequency of vRNA in blood, and to identify associated clinical characteristics. We performed RT-PCR in serum samples from a UK clinical cohort of acute and convalescent COVID-19 cases (n=212), together with convalescent plasma samples collected by NHS Blood and Transplant (NHSBT) (n=462 additional samples). To determine whether PCR-positive blood samples could pose an infection risk, we attempted virus isolation from a subset of RNA-positive samples. Results: We identified 28 relevant studies, reporting SARS-CoV-2 RNA in 0-76% of blood samples; pooled estimate 10% (95%CI 5-18%). Among serum samples from our clinical cohort, 27/212 (12.7%) had SARS-CoV-2 RNA detected by RT-PCR. RNA detection occurred in samples up to day 20 post symptom onset, and was associated with more severe disease (multivariable odds ratio 7.5). Across all samples collected ≥28 days post symptom onset, 0/494 (0%, 95%CI 0-0.7%) had vRNA detected. Among our PCR-positive samples, cycle threshold (ct) values were high (range 33.5-44.8), suggesting low vRNA copy numbers. PCR-positive sera inoculated into cell culture did not produce any cytopathic effect or yield an increase in detectable SARS-CoV-2 RNA. Conclusions: vRNA was detectable at low viral loads in a minority of serum samples collected in acute infection, but was not associated with infectious SARS-CoV-2 (within the limitations of the assays used). This work helps to inform biosafety precautions for handling blood products from patients with current or previous COVID-19.

Convalescent plasma therapy for the treatment of patients with COVID-19: Assessment of methods available for antibody detection and their correlation with neutralising antibody levels.

INTRODUCTION: The lack of approved specific therapeutic agents to treat coronavirus disease (COVID-19) associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has led to the rapid implementation of convalescent plasma therapy (CPT) trials in many countries, including the United Kingdom. Effective CPT is likely to require high titres of neutralising antibody (nAb) in convalescent donations. Understanding the relationship between functional neutralising antibodies and antibody levels to specific SARS-CoV-2 proteins in scalable assays will be crucial for the success of a large-scale collection. We assessed whether neutralising antibody titres correlated with reactivity in a range of enzyme-linked immunosorbent assays (ELISA) targeting the spike (S) protein, the main target for human immune response. METHODS: Blood samples were collected from 52 individuals with a previous laboratory-confirmed SARS-CoV-2 infection. These were assayed for SARS-CoV-2 nAbs by microneutralisation and pseudo-type assays and for antibodies by four different ELISAs. Receiver operating characteristic (ROC) analysis was used to further identify sensitivity and specificity of selected assays to identify samples containing high nAb levels. RESULTS: All samples contained SARS-CoV-2 antibodies, whereas neutralising antibody titres of greater than 1:20 were detected in 43 samples (83% of those tested) and >1:100 in 22 samples (42%). The best correlations were observed with EUROimmun immunoglobulin G (IgG) reactivity (Spearman Rho correlation coefficient 0.88; p < 0.001). Based on ROC analysis, EUROimmun would detect 60% of samples with titres of >1:100 with 100% specificity using a reactivity index of 9.1 (13/22). DISCUSSION: Robust associations between nAb titres and reactivity in several ELISA-based antibody tests demonstrate their possible utility for scaled-up production of convalescent plasma containing potentially therapeutic levels of anti-SARS-CoV-2 nAbs.

Convalescent plasma treatment for SARS-CoV-2 infection: analysis of the first 436 donors in England, 22 April to 12 May 2020.

Serological reactivity was analysed in plasma from 436 individuals with a history of disease compatible with COVID-19, including 256 who had been laboratory-confirmed with SARS-CoV-2 infection. Over 99% of laboratory-confirmed cases developed a measurable antibody response (254/256) and 88% harboured neutralising antibodies (226/256). Antibody levels declined over 3 months following diagnosis, emphasising the importance of the timing of convalescent plasma collections. Binding antibody measurements can inform selection of convalescent plasma donors with high neutralising antibody levels.