Postpandemic Sentinel Surveillance of Respiratory Diseases in the Context of the World Health Organization Mosaic Framework: Protocol for a Development and Evaluation Study Involving the English Primary Care Network 2023-2024

BACKGROUND

Prepandemic sentinel surveillance focused on improved management of winter pressures, with influenza-like illness (ILI) being the key clinical indicator. The World Health Organization (WHO) global standards for influenza surveillance include monitoring acute respiratory infection (ARI) and ILI. The WHO's mosaic framework recommends that the surveillance strategies of countries include the virological monitoring of respiratory viruses with pandemic potential such as influenza. The Oxford-Royal College of General Practitioner Research and Surveillance Centre (RSC) in collaboration with the UK Health Security Agency (UKHSA) has provided sentinel surveillance since 1967, including virology since 1993.

OBJECTIVE

We aim to describe the RSC's plans for sentinel surveillance in the 2023-2024 season and evaluate these plans against the WHO mosaic framework.

METHODS

Our approach, which includes patient and public involvement, contributes to surveillance objectives across all 3 domains of the mosaic framework. We will generate an ARI phenotype to enable reporting of this indicator in addition to ILI. These data will support UKHSA's sentinel surveillance, including vaccine effectiveness and burden of disease studies. The panel of virology tests analyzed in UKHSA's reference laboratory will remain unchanged, with additional plans for point-of-care testing, pneumococcus testing, and asymptomatic screening. Our sampling framework for serological surveillance will provide greater representativeness and more samples from younger people. We will create a biomedical resource that enables linkage between clinical data held in the RSC and virology data, including sequencing data, held by the UKHSA. We describe the governance framework for the RSC.

RESULTS

We are co-designing our communication about data sharing and sampling, contextualized by the mosaic framework, with national and general practice patient and public involvement groups. We present our ARI digital phenotype and the key data RSC network members are requested to include in computerized medical records. We will share data with the UKHSA to report vaccine effectiveness for COVID-19 and influenza, assess the disease burden of respiratory syncytial virus, and perform syndromic surveillance. Virological surveillance will include COVID-19, influenza, respiratory syncytial virus, and other common respiratory viruses. We plan to pilot point-of-care testing for group A streptococcus, urine tests for pneumococcus, and asymptomatic testing. We will integrate test requests and results with the laboratory-computerized medical record system. A biomedical resource will enable research linking clinical data to virology data. The legal basis for the RSC's pseudonymized data extract is The Health Service (Control of Patient Information) Regulations 2002, and all nonsurveillance uses require research ethics approval.

CONCLUSIONS

The RSC extended its surveillance activities to meet more but not all of the mosaic framework's objectives. We have introduced an ARI indicator. We seek to expand our surveillance scope and could do more around transmissibility and the benefits and risks of nonvaccine therapies.

Robust and sensitive amplicon-based whole-genome sequencing assay of respiratory syncytial virus subtype A and B

Prevention of respiratory syncytial virus (RSV) infection is now a global health priority, with a long-acting monoclonal antibody and two RSV vaccines recently licenced for clinical use. Most licenced and candidate interventions target the RSV fusion (RSV-F) protein. New interventions may be associated with the spread of mutations, reducing susceptibility to antibody neutralization in RSV-F. There is a need for ongoing longitudinal global surveillance of circulating RSV strains. To achieve this large-scale genomic surveillance, a reliable, high-throughput RSV sequencing assay is required. Here we report an improved high-throughput RSV whole-genome sequencing (WGS) assay performed directly on clinical samples without additional enrichment, using a 4-primer-pool, short-amplicon PCR-tiling approach that is suitable for short-read sequencing platforms. Using upper respiratory tract (URT) RSV-positive clinical samples obtained from a sentinel network of primary care providers and from hospital patients (29.7% and 70.2%, respectively; n = 1,037), collected over the period 2019 to 2023, this assay had a threshold of approximately 4 × 103 to 8 × 103 copies/mL (RSV-B and RSV-A sub-types, respectively) as the lowest amount of virus needed in the sample to achieve >96% of whole-genome coverage at a high-quality level. Using a Ct value of 31 as an empirical cut-off, the overall assay success rate of obtaining >90% genome coverage at a read depth minimum of 20 was 96.83% for clinical specimens successfully sequenced from a total of 1,071. The RSV WGS approach described in this study has increased sensitivity compared to previous approaches and can be applied to clinical specimens without the requirement for enrichment. The updated approach produces sequences of high quality consistently and cost-effectively, suitable for implementation to underpin national programs for the surveillance of RSV genomic variation.

IMPORTANCE

In this paper, we report an improved high-throughput respiratory syncytial virus (RSV) whole-genome sequencing (WGS) assay performed directly on clinical samples, using a 4-primer-pool, short-amplicon PCR-tiling approach that is suitable for short-read sequencing platforms. The RSV WGS approach described in this study has increased sensitivity compared to previous approaches and can be applied to clinical specimens without the requirement for enrichment. The updated approach produces sequences of high quality consistently and cost-effectively, suitable for implementation to underpin national and global programs for the surveillance of RSV genomic variation. The quality of sequence produced is essential for preparedness for new interventions in monitoring antigenic escape, where a single point mutation might lead to a reduction in antibody binding effectiveness and neutralizing activity, or indeed in the monitoring of retaining susceptibility to neutralization by existing and new interventions.

Influenza vaccination during the 2021/22 season: A data-linkage test-negative case-control study of effectiveness against influenza requiring emergency care in England and serological analysis of primary care patients

We present England 2021/22 end-of-season adjusted vaccine effectiveness (aVE) against laboratory confirmed influenza related emergency care use in children aged 1-17 and in adults aged 50+, and serological findings in vaccinated vs unvaccinated adults by hemagglutination inhibition assay. Influenza vaccination has been routinely offered to all children aged 2-10 years and adults aged 65 years + in England. In 2021/22, the offer was extended to children to age 15 years, and adults aged 50-64 years. Influenza activity rose during the latter half of the 2021/22 season, while remaining comparatively low due to COVID-19 pandemic control measures. Influenza A(H3N2) strains predominated. A test negative design was used to estimate aVE by vaccine type. Cases and controls were identified within a sentinel laboratory surveillance system. Vaccine histories were obtained from the National Immunisation Management Service (NIMS), an influenza and COVID-19 vaccine registry. These were linked to emergency department presentations (excluding accidents) with respiratory swabbing ≤ 14 days before or ≤ 7 days after presentation. Amongst adults, 423 positive and 32,917 negative samples were eligible for inclusion, and 145 positive and 6,438 negative samples among children. Those admitted to hospital were further identified. In serology against the circulating A(H3N2) A/Bangladesh/4005/2020-like strain, 61 % of current season adult vaccinees had titres ≥ 1:40 compared to 17 % of those unvaccinated in 2020/21 or 2021/22 (p < 0.001). We found good protection from influenza vaccination against influenza requiring emergency care in children (72.7 % [95 % CI 52.7, 84.3 %]) and modest effectiveness in adults (26.1 % [95 % CI 4.5, 42.8 %]). Adult VE was higher for A(H1N1) (81 % [95 % CI 50, 93 %]) than A(H3N2) (33 % [95 % CI 6, 53 %]). Consistent protection was observable across preschool, primary and secondary school aged children. Imperfect test specificity combined with very low prevalence may have biased estimates towards null. With limited influenza circulation, the study could not determine differences by vaccine types.

Optimizing mood prior to influenza vaccination in older adults: A three-arm randomized controlled trial

OBJECTIVE

This trial explored the psychological and immunological effects of two brief interventions, targeting improving positive mood, administered to older adults immediately prior to influenza vaccination. The primary aim was to examine whether the interventions resulted in greater positive mood compared to usual care, and if so, which was superior. Secondary outcomes included antibody responses to vaccination and feasibility of collecting clinical outcome data (e.g., respiratory infections).

METHOD

Six hundred and fifty-four older adults (65-85 years) participated in a three-arm, parallel, randomized controlled trial between September 2019 and May 2020. Immediately prior to receiving an adjuvanted trivalent influenza vaccine (Fluad, Seqirus UK Ltd), participants viewed one of two brief (15-min) video-based positive mood interventions (one fixed content, one allowing participant choice) or received usual care. State affect was measured immediately prior to, and following, intervention exposure or usual care. Antibody responses were measured prevaccination and 4 weeks postvaccination. Clinical outcomes were extracted from primary care records for 6 months following vaccination.

RESULTS

Both interventions were equally effective at improving mood prior to vaccination compared to usual care. Antibody responses were highly robust with postvaccination seroprotection rates of > 88% observed for all vaccine strains. Antibody responses did not significantly differ between groups. Clinical outcome data were feasible to collect.

CONCLUSIONS

Brief psychological interventions can improve mood prior to vaccination. However, altering antibody responses to highly immunogenic adjuvanted vaccines may require more targeted or prolonged interventions. The provision of choice did not notably enhance the interventions impact on mood or antibody outcomes. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

A case of swine influenza A(H1N2)v in England, November 2023

Under International Health Regulations from 2005, a human infection caused by a novel influenza A virus variant is considered an event that has potential for high public health impact and is immediately notifiable to the World Health Organisation. We here describe the clinical, epidemiological and virological features of a confirmed human case of swine influenza A(H1N2)v in England detected through community respiratory virus surveillance. Swabbing and contact tracing helped refine public health risk assessment, following this unusual and unexpected finding.

Serum HCoV-spike specific antibodies do not protect against subsequent SARS-CoV-2 infection in children and adolescents

SARS-CoV-2 infections in children are generally asymptomatic or mild and rarely progress to severe disease and hospitalization. Why this is so remains unclear. Here we explore the potential for protection due to pre-existing cross-reactive seasonal coronavirus antibodies and compare the rate of antibody decline for nucleocapsid and spike protein in serum and oral fluid against SARS-CoV-2 within the pediatric population. No differences in seasonal coronaviruses antibody concentrations were found at baseline between cases and controls, suggesting no protective effect from pre-existing immunity against seasonal coronaviruses. Antibodies against seasonal betacoronaviruses were boosted in response to SARS-CoV-2 infection. In serum, anti-nucleocapsid antibodies fell below the threshold of positivity more quickly than anti-spike protein antibodies. These findings add to our understanding of protection against infection with SARS-CoV-2 within the pediatric population, which is important when considering pediatric SARS-CoV-2 immunization policies.

Early mucosal events promote distinct mucosal and systemic antibody responses to live attenuated influenza vaccine

Compared to intramuscular vaccines, nasally administered vaccines have the advantage of inducing local mucosal immune responses that may block infection and interrupt transmission of respiratory pathogens. Live attenuated influenza vaccine (LAIV) is effective in preventing influenza in children, but a correlate of protection for LAIV remains unclear. Studying young adult volunteers, we observe that LAIV induces distinct, compartmentalized, antibody responses in the mucosa and blood. Seeking immunologic correlates of these distinct antibody responses we find associations with mucosal IL-33 release in the first 8 hours post-inoculation and divergent CD8+ and circulating T follicular helper (cTfh) T cell responses 7 days post-inoculation. Mucosal antibodies are induced separately from blood antibodies, are associated with distinct immune responses early post-inoculation, and may provide a correlate of protection for mucosal vaccination. This study was registered as NCT04110366 and reports primary (mucosal antibody) and secondary (blood antibody, and nasal viral load and cytokine) endpoint data.

Paediatric acute hepatitis of unknown aetiology: a national investigation and adenoviraemia case-control study in the UK

BACKGROUND

An increase in acute severe hepatitis of unknown aetiology in previously healthy children in the UK in March, 2022, triggered global case-finding. We aimed to describe UK epidemiological investigations of cases and their possible causes.

METHODS

We actively surveilled unexplained paediatric acute hepatitis (transaminase >500 international units per litre) in children younger than 16 years presenting since Jan 1, 2022, through notifications from paediatricians, microbiologists, and paediatric liver units; we collected demographic, clinical, and exposure information. Then, we did a case-control study to investigate the association between adenoviraemia and other viruses and case-status using multivariable Firth penalised logistic regression. Cases aged 1-10 years and tested for adenovirus were included and compared with controls (ie, children admitted to hospital with an acute non-hepatitis illness who had residual blood samples collected between Jan 1 and May 28, 2022, and without known laboratory-confirmed diagnosis or previous adenovirus testing). Controls were frequency-matched on sex, age band, sample months, and nation or supra-region with randomised selection. We explored temporal associations between frequency of circulating viruses identified through routine laboratory pathogen surveillance and occurrence of cases by linear regression. SARS-CoV-2 seropositivity of cases was examined against residual serum from age-matched clinical comparison groups.

FINDINGS

Between Jan 1 and July 4, 2022, 274 cases were identified (median age 3 years [IQR 2-5]). 131 (48%) participants were male, 142 (52%) were female, and one (<1%) participant had sex data unknown. Jaundice (195 [83%] of 235) and gastrointestinal symptoms (202 [91%] of 222) were common. 15 (5%) children required liver transplantation and none died. Adenovirus was detected in 172 (68%) of 252 participants tested, regardless of sample type; 137 (63%) of 218 samples were positive for adenovirus in the blood. For cases that were successfully genotyped, 58 (81%) of 72 had Ad41F, and 57 were identified as positive via blood samples (six of these were among participants who had undergone a transplant). In the case-control analysis, adenoviraemia was associated with hepatitis case-status (adjusted OR 37·4 [95% CI 15·5-90·3]). Increases in the detection of adenovirus from faecal samples, but not other infectious agents, in routine laboratory pathogen surveillance correlated with hepatitis cases 4 weeks later, which independently suggested an association (β 0·06 [95% CI 0·02-0·11]). No association was identified for SARS-CoV-2 antibody seropositivity.

INTERPRETATION

We observed an association between adenovirus 41F viraemia and paediatric acute hepatitis. These results can inform diagnostic testing recommendations, clinical management, and exploratory in vitro or clinical studies of paediatric acute hepatitis of unknown aetiology. The role of potential co-factors, including other viruses and host susceptibility, requires further investigation.

FUNDING

None.

High attack rate in a large care home outbreak of SARS-CoV-2 BA.2.86, East of England, August 2023

We investigated an outbreak of SARS-CoV-2 variant BA.2.86 in an East of England care home. We identified 45 infections (33 residents, 12 staff), among 38 residents and 66 staff. Twenty-nine of 43 PCR swabs were sequenced, all of which were variant BA.2.86. The attack rate among residents was 87%, 19 were symptomatic, and one was hospitalised. Twenty-four days after the outbreak started, no cases were still unwell. Among the 33 resident cases, 29 had been vaccinated 4 months earlier.

Genomic investigations of unexplained acute hepatitis in children

Since its first identification in Scotland, over 1,000 cases of unexplained paediatric hepatitis in children have been reported worldwide, including 278 cases in the UK1. Here we report an investigation of 38 cases, 66 age-matched immunocompetent controls and 21 immunocompromised comparator participants, using a combination of genomic, transcriptomic, proteomic and immunohistochemical methods. We detected high levels of adeno-associated virus 2 (AAV2) DNA in the liver, blood, plasma or stool from 27 of 28 cases. We found low levels of adenovirus (HAdV) and human herpesvirus 6B (HHV-6B) in 23 of 31 and 16 of 23, respectively, of the cases tested. By contrast, AAV2 was infrequently detected and at low titre in the blood or the liver from control children with HAdV, even when profoundly immunosuppressed. AAV2, HAdV and HHV-6 phylogeny excluded the emergence of novel strains in cases. Histological analyses of explanted livers showed enrichment for T cells and B lineage cells. Proteomic comparison of liver tissue from cases and healthy controls identified increased expression of HLA class 2, immunoglobulin variable regions and complement proteins. HAdV and AAV2 proteins were not detected in the livers. Instead, we identified AAV2 DNA complexes reflecting both HAdV-mediated and HHV-6B-mediated replication. We hypothesize that high levels of abnormal AAV2 replication products aided by HAdV and, in severe cases, HHV-6B may have triggered immune-mediated hepatic disease in genetically and immunologically predisposed children.

Haemagglutination inhibition and virus microneutralisation serology assays: use of harmonised protocols and biological standards in seasonal influenza serology testing and their impact on inter-laboratory variation and assay correlation: A FLUCOP collaborative study

Introduction

The haemagglutination inhibition assay (HAI) and the virus microneutralisation assay (MN) are long-established methods for quantifying antibodies against influenza viruses. Despite their widespread use, both assays require standardisation to improve inter-laboratory agreement in testing. The FLUCOP consortium aims to develop a toolbox of standardised serology assays for seasonal influenza. Building upon previous collaborative studies to harmonise the HAI, in this study the FLUCOP consortium carried out a head-to-head comparison of harmonised HAI and MN protocols to better understand the relationship between HAI and MN titres, and the impact of assay harmonisation and standardisation on inter-laboratory variability and agreement between these methods.

Methods

In this paper, we present two large international collaborative studies testing harmonised HAI and MN protocols across 10 participating laboratories. In the first, we expanded on previously published work, carrying out HAI testing using egg and cell isolated and propagated wild-type (WT) viruses in addition to high-growth reassortants typically used influenza vaccines strains using HAI. In the second we tested two MN protocols: an overnight ELISA-based format and a 3-5 day format, using reassortant viruses and a WT H3N2 cell isolated virus. As serum panels tested in both studies included many overlapping samples, we were able to look at the correlation of HAI and MN titres across different methods and for different influenza subtypes.

Results

We showed that the overnight ELISA and 3-5 day MN formats are not comparable, with titre ratios varying across the dynamic range of the assay. However, the ELISA MN and HAI are comparable, and a conversion factor could possibly be calculated. In both studies, the impact of normalising using a study standard was investigated, and we showed that for almost every strain and assay format tested, normalisation significantly reduced inter-laboratory variation, supporting the continued development of antibody standards for seasonal influenza viruses. Normalisation had no impact on the correlation between overnight ELISA and 3-5 day MN formats.

An external quality assessment feasibility study; cross laboratory comparison of haemagglutination inhibition assay and microneutralization assay performance for seasonal influenza serology testing: A FLUCOP study

Introduction

External Quality Assessment (EQA) schemes are designed to provide a snapshot of laboratory proficiency, identifying issues and providing feedback to improve laboratory performance and inter-laboratory agreement in testing. Currently there are no international EQA schemes for seasonal influenza serology testing. Here we present a feasibility study for conducting an EQA scheme for influenza serology methods.

Methods

We invited participant laboratories from industry, contract research organizations (CROs), academia and public health institutions who regularly conduct hemagglutination inhibition (HAI) and microneutralization (MN) assays and have an interest in serology standardization. In total 16 laboratories returned data including 19 data sets for HAI assays and 9 data sets for MN assays.

Results

Within run analysis demonstrated good laboratory performance for HAI, with intrinsically higher levels of intra-assay variation for MN assays. Between run analysis showed laboratory and strain specific issues, particularly with B strains for HAI, whilst MN testing was consistently good across labs and strains. Inter-laboratory variability was higher for MN assays than HAI, however both assays showed a significant reduction in inter-laboratory variation when a human sera pool is used as a standard for normalization.

Discussion

This study has received positive feedback from participants, highlighting the benefit such an EQA scheme would have on improving laboratory performance, reducing inter laboratory variation and raising awareness of both harmonized protocol use and the benefit of biological standards for seasonal influenza serology testing.

ADCC: An underappreciated correlate of cross-protection against influenza?

In this short review, we summarized the results obtained with an assay to detect influenza virus-specific antibodies that mediate ADCC, which was developed and evaluated within the framework of the IMI-funded project "FLUCOP". HA-specific ADCC mediating antibodies were detected in serum samples from children and adults pre- and post-vaccination with monovalent, trivalent, or quadrivalent seasonal influenza vaccines, or following infection with H1N1pdm09 virus. Additionally, using chimeric influenza HA proteins, the presence of HA-stalk-specific ADCC mediating antibodies after vaccination and natural infection with H1N1pdm09 virus was demonstrated. With serum samples obtained from children that experienced a primary infection with an influenza B virus, we showed that primary infection induces HA-specific ADCC-mediating antibodies that cross-reacted with HA from influenza B viruses from the heterologous lineage. These cross-reactive antibodies were found to be directed to the HA stalk region. Antibodies directed to the influenza B virus HA head mediated low levels of ADCC. Finally, vaccination with a recombinant modified vaccinia virus Ankara expressing the HA gene of a clade 1 A(H5N1) highly pathogenic avian influenza virus led to the induction of ADCC-mediating antibodies, which cross-reacted with H5 viruses of antigenically distinct clades. Taken together, it is clear that virus-specific antibodies induced by infection or vaccination have immunological functionalities in addition to neutralization. These functionalities could contribute to protective immunity. The functional profiling of vaccine-induced antibodies may provide further insight into the effector functions of virus-specific antibodies and their contribution to virus-specific immunity.

Validation of a Harmonized Enzyme-Linked-Lectin-Assay (ELLA-NI) Based Neuraminidase Inhibition Assay Standard Operating Procedure (SOP) for Quantification of N1 Influenza Antibodies and the Use of a Calibrator to Improve the Reproducibility of the ELLA-NI With Reverse Genetics Viral and Recombinant Neuraminidase Antigens: A FLUCOP Collaborative Study

Current vaccination strategies against influenza focus on generating an antibody response against the viral haemagglutination surface protein, however there is increasing interest in neuraminidase (NA) as a target for vaccine development. A critical tool for development of vaccines that target NA or include an NA component is available validated serology assays for quantifying anti-NA antibodies. Additionally serology assays have a critical role in defining correlates of protection in vaccine development and licensure. Standardisation of these assays is important for consistent and accurate results. In this study we first validated a harmonized enzyme-linked lectin assay (ELLA)- Neuraminidase Inhibition (NI) SOP for N1 influenza antigen and demonstrated the assay was precise, linear, specific and robust within classical acceptance criteria for neutralization assays for vaccine testing. Secondly we tested this SOP with NA from influenza B viruses and showed the assay performed consistently with both influenza A and B antigens. Third, we demonstrated that recombinant NA (rNA) could be used as a source of antigen in ELLA-NI. In addition to validating a harmonized SOP we finally demonstrated a clear improvement in inter-laboratory agreement across several studies by using a calibrator. Importantly we showed that the use of a calibrator significantly improved agreement when using different sources of antigen in ELLA-NI, namely reverse genetics viruses and recombinant NA. We provide a freely available and detailed harmonized SOP for ELLA-NI. Our results add to the growing body of evidence in support of developing biological standards for influenza serology.

Estimation of Seasonal Influenza Attack Rates and Antibody Dynamics in Children Using Cross-Sectional Serological Data

Directly measuring evidence of influenza infections is difficult, especially in low-surveillance settings such as sub-Saharan Africa. Using a Bayesian model, we estimated unobserved infection times and underlying antibody responses to influenza A/H3N2, using cross-sectional serum antibody responses to 4 strains in children aged 24-60 months. Among the 242 individuals, we estimated a variable seasonal attack rate and found that most children had ≥1 infection before 2 years of age. Our results are consistent with previously published high attack rates in children. The modeling approach highlights how cross-sectional serological data can be used to estimate epidemiological dynamics.

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.

Antibody persistence and neutralising activity in primary school students and staff: Prospective active surveillance, June to December 2020, England

BACKGROUND

Prospective, longitudinal SARS-CoV-2 sero-surveillance in schools across England was initiated after the first national lockdown, allowing comparison of child and adult antibody responses over time.

METHODS

Prospective active serological surveillance in 46 primary schools in England tested for SARS-CoV-2 antibodies during June, July and December 2020. Samples were tested for nucleocapsid (N) and receptor binding domain (RBD) antibodies, to estimate antibody persistence at least 6 months after infection, and for the correlation of N, RBD and live virus neutralising activity.

FINDINGS

In June 2020, 1,344 staff and 835 students were tested. Overall, 11.5% (95%CI: 9.4-13.9) and 11.3% (95%CI: 9.2-13.6; p = 0.88) of students had nucleoprotein and RBD antibodies, compared to 15.6% (95%CI: 13.7-17.6) and 15.3% (95%CI: 13.4-17.3; p = 0.83) of staff. Live virus neutralising activity was detected in 79.8% (n = 71/89) of nucleocapsid and 85.5% (71/83) of RBD antibody positive children. RBD antibodies correlated more strongly with neutralising antibodies (rs=0.7527; p<0.0001) than nucleocapsid antibodies (rs=0.3698; p<0.0001). A median of 24.4 weeks later, 58.2% (107/184) participants had nucleocapsid antibody seroreversion, compared to 20.9% (33/158) for RBD (p<0.001). Similar seroreversion rates were observed between staff and students for nucleocapsid (p = 0.26) and RBD-antibodies (p = 0.43). Nucleocapsid and RBD antibody quantitative results were significantly lower in staff compared to students (p = 0.028 and <0.0001 respectively) at baseline, but not at 24 weeks (p = 0.16 and p = 0.37, respectively).

INTERPRETATION

The immune response in children following SARS-CoV-2 infection was robust and sustained (>6 months) but further work is required to understand the extent to which this protects against reinfection.

Seasonal trivalent inactivated influenza vaccine with topical imiquimod in immunocompromised patients: A randomized controlled trial

BACKGROUND

The effect of the Toll-like receptor 7 agonist imiquimod before intradermal (ID) or intramuscular (IM) influenza vaccine in immunocompromised hosts is unknown.

METHODS

In this open-label randomized controlled trial, kidney transplant recipients (KT) and people living with HIV (PLWH) were randomized to receive IM trivalent inactivated influenza vaccine alone (IM), IM vaccine after topical imiquimod (imi+IM) or ID vaccine after topical imiquimod (imi+ID). Immunogenicity was assessed by hemagglutination inhibition assay. The primary outcome was vaccine response, defined as seroconversion to at least one viral strain at day 21.

RESULTS

Seventy patients (35 KT and 35 PLWH) received IM (24), imi+IM (22), or imi+ID (24) vaccine. Vaccine response was 61% (14/23) with IM, 59% (13/22) with imi+IM, and 65% (15/23) with imi+ID vaccine (P = 0.909). Vaccine response was associated with HIV infection compared to kidney transplantation (adjusted-OR 3.74, 95% CI 1.25 - 11.23, P = 0.019), but not with imiquimod application nor ID injection. After vaccination, seroprotection to all viral strains was 79% (19/24) with IM, 68% (15/22) with imi+IM, and 70% (16/23) with imi+ID (P = 0.657). We did not observe any vaccine-related severe adverse event.

CONCLUSIONS

In our study, topical imiquimod did not improve the immunogenicity of influenza vaccine in KT and in PLWH.

Seroprevalence of SARS-CoV-2 among Blood Donors and Changes after Introduction of Public Health and Social Measures, London, UK

We describe results of testing blood donors in London, UK, for severe acute respiratory disease coronavirus 2 (SARS-CoV-2) IgG before and after lockdown measures. Anonymized samples from donors 17–69 years of age were tested using 3 assays: Euroimmun IgG, Abbott IgG, and an immunoglobulin receptor-binding domain assay developed by Public Health England. Seroprevalence increased from 3.0% prelockdown (week 13, beginning March 23, 2020) to 10.4% during lockdown (weeks 15–16) and 12.3% postlockdown (week 18) by the Abbott assay. Estimates were 2.9% prelockdown, 9.9% during lockdown, and 13.0% postlockdown by the Euroimmun assay and 3.5% prelockdown, 11.8% during lockdown, and 14.1% postlockdown by the receptor-binding domain assay. By early May 2020, nearly 1 in 7 donors had evidence of past SARS-CoV-2 infection. Combining results from the Abbott and Euroimmun assays increased seroprevalence by 1.6%, 2.3%, and 0.6% at the 3 timepoints compared with Euroimmun alone, demonstrating the value of using multiple assays.

Robust SARS-CoV-2-specific T cell immunity is maintained at 6 months following primary infection

The immune response to SARS-CoV-2 is critical in controlling disease, but there is concern that waning immunity may predispose to reinfection. We analyzed the magnitude and phenotype of the SARS-CoV-2-specific T cell response in 100 donors at 6 months following infection. T cell responses were present by ELISPOT and/or intracellular cytokine staining analysis in all donors and characterized by predominant CD4+ T cell responses with strong interleukin (IL)-2 cytokine expression. Median T cell responses were 50% higher in donors who had experienced a symptomatic infection, indicating that the severity of primary infection establishes a 'set point' for cellular immunity. T cell responses to spike and nucleoprotein/membrane proteins were correlated with peak antibody levels. Furthermore, higher levels of nucleoprotein-specific T cells were associated with preservation of nucleoprotein-specific antibody level although no such correlation was observed in relation to spike-specific responses. In conclusion, our data are reassuring that functional SARS-CoV-2-specific T cell responses are retained at 6 months following infection.

Seroprevalence of SARS-CoV-2 antibodies in university students: Cross-sectional study, December 2020, England

Background

In England, the reopening of universities in September 2020 coincided with a rapid increase in SARS-CoV-2 infection rates in university aged young adults. This study aimed to estimate SARS-CoV-2 antibody prevalence in students attending universities that had experienced a COVID-19 outbreak after reopening for the autumn term in September 2020.

Methods

A cross-sectional serosurvey was conducted during 02–11 December 2020 in students aged ≤ 25 years across five universities in England. Blood samples for SARS-CoV-2 antibody testing were obtained using a self-sampling kit and analysed using the Abbott SARS-CoV-2 N antibody and/or an in-house receptor binding domain (RBD) assay.

Findings

SARS-CoV-2 seroprevalence in 2,905 university students was 17.8% (95%CI, 16.5–19.3), ranging between 7.6%-29.7% across the five universities. Seropositivity was associated with being younger likely to represent first year undergraduates (aOR 3.2, 95% CI 2.0–4.9), living in halls of residence (aOR 2.1, 95% CI 1.7–2.7) and sharing a kitchen with an increasing number of students (shared with 4–7 individuals, aOR 1.43, 95%CI 1.12–1.82; shared with 8 or more individuals, aOR 1.53, 95% CI 1.04–2.24). Seropositivity was 49% in students living in halls of residence that reported high SARS-CoV-2 infection rates (>8%) during the autumn term.

Interpretation

Despite large numbers of cases and outbreaks in universities, less than one in five students (17.8%) overall had SARS-CoV-2 antibodies at the end of the autumn term in England. In university halls of residence affected by a COVID-19 outbreak, however, nearly half the resident students became infected and developed SARS-CoV-2 antibodies.

Pre-existing influenza-specific nasal IgA or nasal viral infection does not affect live attenuated influenza vaccine immunogenicity in children

The United Kingdom has a national immunization programme which includes annual influenza vaccination in school-aged children, using live attenuated influenza vaccine (LAIV). LAIV is given annually, and it is unclear whether repeat administration can affect immunogenicity. Because LAIV is delivered intranasally, pre-existing local antibody might be important. In this study, we analysed banked samples from a study performed during the 2017/18 influenza season to investigate the role of pre-existing influenza-specific nasal immunoglobulin (Ig)A in children aged 6-14 years. Nasopharyngeal swabs were collected prior to LAIV immunization to measure pre-existing IgA levels and test for concurrent upper respiratory tract viral infections (URTI). Oral fluid samples were taken at baseline and 21-28 days after LAIV to measure IgG as a surrogate of immunogenicity. Antibody levels at baseline were compared with a pre-existing data set of LAIV shedding from the same individuals, measured by reverse transcription-polymerase chain reaction. There was detectable nasal IgA specific to all four strains in the vaccine at baseline. However, baseline nasal IgA did not correlate with the fold change in IgG response to the vaccine. Baseline nasal IgA also did not have an impact upon whether vaccine virus RNA was detectable after immunization. There was no difference in fold change of antibody between individuals with and without an URTI at the time of immunization. Overall, we observed no effect of pre-existing influenza-specific nasal antibody levels on immunogenicity, supporting annual immunization with LAIV in children.

Robust antibody responses in 70-80-year-olds 3 weeks after the first or second doses of Pfizer/BioNTech COVID-19 vaccine, United Kingdom, January to February 2021

Sera were collected from 185 adults aged ≥ 70 years in London to evaluate the immune response to COVID-19 vaccines. A single dose of Pfizer/BioNtech vaccine resulted in > 94% seropositivity after 3 weeks in naïve individuals using the Roche Spike antibody assay, while two doses produced very high spike antibody levels, significantly higher than convalescent sera from mild-to-moderate PCR-confirmed adult cases. Our findings support the United Kingdom's approach of prioritising the first dose and delaying the second dose of COVID-19 vaccine.

Antibodies to SARS-CoV-2 protect against re-infection during outbreaks in care homes, September and October 2020

Two London care homes experienced a second COVID-19 outbreak, with 29/209 (13.9%) SARS-CoV-2 RT-PCR-positive cases (16/103 residents, 13/106 staff). In those with prior SARS-CoV-2 exposure, 1/88 (1.1%) individuals (antibody positive: 87; RT-PCR-positive: 1) became PCR-positive compared with 22/73 (30.1%) with confirmed seronegative status. After four months protection offered by prior infection against re-infection was 96.2% (95% confidence interval (CI): 72.7-99.5%) using risk ratios from comparison of proportions and 96.1% (95% CI: 78.8-99.3%) using a penalised logistic regression model.

Inactivated pandemic 2009 H1N1 influenza A virus human vaccines have different efficacy after homologous challenge in the ferret model

Background

The 2009 pandemic H1N1 (A(H1N1)pdm09) influenza A virus (IAV) has replaced the previous seasonal H1N1 strain in humans and continues to circulate worldwide. The comparative performance of inactivated A(H1N1)pdm09 influenza vaccines remains of considerable interest. The objective of this study was to evaluate the efficacy of two licensed A(H1N1)pdm09 inactivated vaccines (AS03B adjuvanted split virion Pandemrix from GlaxoSmithKline and referred here as (V1) and non‐adjuvanted whole virion Celvapan from Baxter and referred here as (V2)) in ferrets as a pre‐clinical model for human disease intervention.

Methods

Naïve ferrets were divided into two groups (V1 and V2) and immunised intramuscularly with two different A/California/07/2009‐derived inactivated vaccines, V1 administered in a single dose and V2 administered in 2 doses separated by 21 days. Six weeks after the first immunisation, vaccinated animals and a non‐vaccinated control (NVC) group were intra‐nasally challenged with 10^6.5 TCID₅₀ of the isolate A/England/195/2009 A(H1N1)pdm09 with 99.1% amino acid identity to the vaccine strain. Clinical signs, lung histopathology, viral quantification and antibody responses were evaluated.

Results and Conclusions

Results revealed important qualitative differences in the performance of both inactivated vaccines in relation to protection against challenge with a comparable virus in a naive animal (ferret) model of human disease. Vaccine V1 limited and controlled viral shedding and reduced lower respiratory tract infection. In contrast, vaccine V2 did not control infection and animals showed sustained viral shedding and delayed lower respiratory infection, resulting in pulmonary lesions, suggesting lower efficacy of V2 vaccine.

Cell-Mediated Immune Responses After Influenza Vaccination of Solid Organ Transplant Recipients: Secondary Outcomes Analyses of a Randomized Controlled Trial

BACKGROUND

Despite annual immunization, solid organ transplant (SOT) patients remain at increased risk for severe influenza infection because of suboptimal vaccine immunogenicity. We aimed to compare the CD4+ and CD8+ T-cell responses of the high-dose (HD) and the standard-dose (SD) trivalent inactivated vaccine.

METHODS

We collected peripheral blood mononuclear cells pre- and postimmunization from 60 patients enrolled in a randomized trial of HD versus SD vaccine (30 HD; 30 SD) during the 2016-2017 influenza season.

RESULTS

The HD vaccine elicited significantly greater monofunctional and polyfunctional CD4+ and CD8+ T-cell responses against influenza A/H1N1, A/H3N2, and B. For example, median vaccine-elicited influenza-specific polyfunctional CD4+ T cells were higher in recipients of the HD than SD vaccine after stimulation with influenza A/H1N1 (1193 vs 0 per 106 CD4+ T cells; P = .003), A/H3N2 (1154 vs 51; P = .008), and B (1102 vs 0; P = .001). Likewise, vaccine-elicited influenza-specific polyfunctional CD8+ T cells were higher in recipients of the HD than SD vaccine after stimulation with influenza B (367 vs 0; P = .002).

CONCLUSIONS

Our study provides novel evidence that HD vaccine elicits greater cellular responses compared with the SD vaccine in SOT recipients, which provides support to preferentially consider use of HD vaccination in the SOT setting.

End of season influenza vaccine effectiveness in adults and children in the United Kingdom in 2017/18

Background

In the United Kingdom (UK), in recent influenza seasons, children are offered a quadrivalent live attenuated influenza vaccine (LAIV4), and eligible adults mainly trivalent inactivated vaccine (TIV).

Aim

To estimate the UK end-of-season 2017/18 adjusted vaccine effectiveness (aVE) and the seroprevalence in England of antibodies against influenza viruses cultured in eggs or tissue.

Methods

This observational study employed the test-negative case–control approach to estimate aVE in primary care. The population-based seroprevalence survey used residual age-stratified samples.

Results

Influenza viruses A(H3N2) (particularly subgroup 3C.2a2) and B (mainly B/Yamagata/16/88-lineage, similar to the quadrivalent vaccine B-virus component but mismatched to TIV) dominated. All-age aVE was 15% (95% confidence interval (CI): −6.3 to 32) against all influenza; −16.4% (95% CI: −59.3 to 14.9) against A(H3N2); 24.7% (95% CI: 1.1 to 42.7) against B and 66.3% (95% CI: 33.4 to 82.9) against A(H1N1)pdm09. For 2–17 year olds, LAIV4 aVE was 26.9% (95% CI: −32.6 to 59.7) against all influenza; −75.5% (95% CI: −289.6 to 21) against A(H3N2); 60.8% (95% CI: 8.2 to 83.3) against B and 90.3% (95% CI: 16.4 to 98.9) against A(H1N1)pdm09. For ≥ 18 year olds, TIV aVE against influenza B was 1.9% (95% CI: −63.6 to 41.2). The 2017 seroprevalence of antibody recognising tissue-grown A(H3N2) virus was significantly lower than that recognising egg-grown virus in all groups except 15–24 year olds.

Conclusions

Overall aVE was low driven by no effectiveness against A(H3N2) possibly related to vaccine virus egg-adaption and a new A(H3N2) subgroup emergence. The TIV was not effective against influenza B. LAIV4 against influenza B and A(H1N1)pdm09 was effective.

Use of traditional serological methods and oral fluids to assess immunogenicity in children aged 2-16 years after successive annual vaccinations with LAIV

Background

The UK introduced quadrivalent live attenuated influenza vaccine (qLAIV) for children in 2013/2014. The impact of annual vaccination on effectiveness and immunogenicity is being assessed.

Method

A phase III/IV open-label study of the immunogenicity of annual vaccination with qLAIV (Fluenz™) was conducted over three consecutive years (2014/15–2016/17) in 254, 249 and 162 children respectively. Serum responses to vaccine components were measured by Haemagglutination Inhibition (HAI) and anti-A(H1N1)pdm09 Neuraminidase (NAI) assays, stratified according to previous receipt of AS03_B-adjuvanted A(H1N1)pdm09 pandemic vaccine in 2009/10. Antibody levels to the A(H1N1)pdm09 and H3N2 vaccine components in oral fluids (OF) were explored using an ELISA.

Findings

More paired pre- and post-vaccination oral fluids (96%) than paired sera (87%) were obtained. Geometric mean titre rises using HAI assays were limited, with maximum rises seen in year one for both influenza B strains when 39% and 43% of subjects seroconverted (95% confidence interval 33–46% and 36–50%, respectively) and year two for influenza H3N2, when 40% (33–46%) individuals seroconverted. Prior pandemic vaccine receipt resulted in higher pre- and post-vaccination A(H1N1)pdm09 HAI titres and lower pre-and post-vaccination NAI (N1 neuraminidase) titres in all three years. OF results were congruent with HAI results; assay specificity compared to HAI was 88.1 and 71.6 percent, and sensitivity was 86.4 and 74.8 percent respectively for A(H1N1)pdm09 and H3N2.

Conclusion

In all three study years, vaccination with qLAIV resulted in poor antibody responses. However, OFs are an alternative specimen type that allows self sampling, can easily be obtained from children, and their analysis leads to similar conclusions as classic serology by HAI. Their suitability for seroprevalence studies should be investigated. We demonstrated a sustained effect from prior receipt of the AS03_B-adjuvanted A(H1N1)pdm09 vaccine, even after repeat vaccination with qLAIV indicating that early exposure to influenza antigens has a significant long lasting effect.

A Double-Blind, Randomized Trial of High-Dose vs Standard-Dose Influenza Vaccine in Adult Solid-Organ Transplant Recipients

Background

The annual standard-dose (SD) influenza vaccine has suboptimal immunogenicity in solid organ transplant recipients (SOTRs). Influenza vaccine that contains higher doses of antigens may lead to greater immunogenicity in this population.

Methods

We conducted a randomized, double-blind trial to compare the safety and immunogenicity of the 2016-2017 high-dose (HD; FluzoneHD, Sanofi) vs SD (Fluviral, GSK) influenza vaccine in adult SOTRs. Preimmunization and 4-week postimmunization sera underwent strain-specific hemagglutination inhibition assay.

Results

We enrolled 172 patients who received study vaccine, and 161 (84 HD; 77 SD) were eligible for analysis. Seroconversion to at least 1 of 3 vaccine antigens was present in 78.6% vs 55.8% in HD vs SD vaccine groups (P < .001), respectively. Seroconversions to A/ H1N1, A/H3N2, and B strains were 40.5% vs 20.5%, 57.1% vs 32.5%, and 58.3% vs 41.6% in HD vs SD vaccine groups (P = .006, P = .002, P = .028, respectively). Post-immunization geometric mean titers of A/H1N1, A/H3N2, and B strains were significantly higher in the HD group (P = .007, P = .002, P = .033). Independent factors associated with seroconversion to at least 1 vaccine strain were the use of HD vaccine (odds ratio [OR], 3.23; 95% confidence interval [CI], 1.56-6.67) and use of mycophenolate doses <2 g daily (OR, 2.76; 95% CI, 1.12-6.76).

Conclusions

HD vaccine demonstrated significantly better immunogenicity than SD vaccine in adult transplant recipients and may be the preferred influenza vaccine for this population.

Clinical Trials Registration

NCT03139565.

Humoral response to natural influenza infection in solid organ transplant recipients

The humoral immune response of transplant recipients to influenza vaccination has been studied in detail. In contrast, the hemagglutinin inhibiting (HI) antibody response evoked by natural influenza infection and its impact on viral kinetics is unknown. In this prospective, multicenter, cohort study of natural influenza infection in transplant recipients, we measured HI antibody titers at presentation and 4 weeks later. Serial nasopharyngeal viral loads were determined using a quantitative influenza A polymerase chain reaction (PCR). We analyzed 196 transplant recipients with influenza infection. In the cohort of organ transplant patients with influenza A (n = 116), seropositivity rates for strain-specific antibodies were 44.0% (95% confidence interval [CI] 31.5-53.2%) at diagnosis and 64.7% (95% CI 55.4-72.9%) 4 weeks postinfection. Seroconversion was observed in 32.8% (95% CI 24.7-41.9%) of the cases. Lung transplant recipients were more likely to seroconvert (P = .002) and vaccine recipients were less likely to seroconvert (P = .024). A subset of patients (n = 30) who were unresponsive to prior vaccination were also unresponsive to natural infection. There was no correlation between viral kinetics and antibody response. This study provides novel data on the seroresponse to influenza infection in transplant patients and its relationship to a number of parameters including a prior vaccination status, virologic measures, and clinical variables.

Serological surveillance of influenza in an English sentinel network: pilot study protocol

BACKGROUND

Rapidly undertaken age-stratified serology studies can produce valuable data about a new emerging infection including background population immunity and seroincidence during an influenza pandemic. Traditionally seroepidemiology studies have used surplus laboratory sera with little or no clinical information or have been expensive detailed population based studies. We propose collecting population based sera from the Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC), a sentinel network with extensive clinical data.

AIM

To pilot a mechanism to undertake population based surveys that collect serological specimens and associated patient data to measure seropositivity and seroincidence due to seasonal influenza, and create a population based serology bank. METHODS AND ANALYSIS: Setting and Participants: We will recruit 6 RCGP RSC practices already taking nasopharyngeal virology swabs. Patients who attend a scheduled blood test will be consented to donate additional blood samples. Approximately 100-150 blood samples will be collected from each of the following age bands - 18- 29, 30- 39, 40- 49, 50- 59, 60- 69 and 70+ years.

METHODS

We will send the samples to the Public Health England (PHE) Seroepidemiology Unit for processing and storage. These samples will be tested for influenza antibodies, using haemagglutination inhibition assays. Serology results will be pseudonymised, sent to the RCGP RSC and combined using existing processes at the RCGP RSC secure hub. The influenza seroprevalence results from the RCGP cohort will be compared against those from the annual PHE influenza residual serosurvey.

ETHICS AND DISSEMINATION

Ethical approval was granted by the Proportionate Review Sub- Committee of the London - Camden & Kings Cross on 6 February 2018. This study received approval from Health Research Authority on 7 February 2018. On completion the results will be made available via peer-reviewed journals.

A Haemophilus sp. dominates the microbiota of sputum from UK adults with non-severe community acquired pneumonia and chronic lung disease

The demographics and comorbidities of patients with community acquired pneumonia (CAP) vary enormously but stratified treatment is difficult because aetiological studies have failed to comprehensively identify the pathogens. Our aim was to describe the bacterial microbiota of CAP and relate these to clinical characteristics in order to inform future trials of treatment stratified by co-morbidity. CAP patients were prospectively recruited at two UK hospitals. We used 16S rRNA gene sequencing to identify the dominant bacteria in sputum and compositional data analysis to determine associations with patient characteristics. We analysed sputum samples from 77 patients and found a Streptococcus sp. and a Haemophilus sp. were the most relatively abundant pathogens. The Haemophilus sp. was more likely to be dominant in patients with pre-existing lung disease, and its relative abundance was associated with qPCR levels of Haemophilus influenzae. The most abundant Streptococcus sp. was associated with qPCR levels of Streptococcus pneumoniae but dominance could not be predicted from clinical characteristics. These data suggest chronic lung disease influences the microbiota of sputum in patients with CAP. This finding could inform a trial of stratifying empirical CAP antibiotics to target Haemophilus spp. in addition to Streptococcus spp. in those with chronic lung disease.

A comparison of viral microneutralization and haemagglutination inhibition assays as measures of seasonal inactivated influenza vaccine immunogenicity in the first year after reduced intensity conditioning, lymphocyte depleted allogeneic haematopoietic stem cell transplant

Traditionally, immune response to influenza vaccines has been measured using the haemagglutination inhibition (HAI) assay. A broader repertoire of techniques including the sensitive viral microneutralization (VMN) assay is now recommended by the European Medicines Agency (EMA). Comparing HAI and VMN, we determined immune response to a trivalent 2015-2016 seasonal inactivated influenza vaccine (SIIV) administered to 28 recipients of allogeneic haematopoietic stem cell transplant (HSCT). Vaccination was within the first-year post-transplant at a median of 78.5 (24-363) days. The proportion of patients with baseline and post-vaccination HAI titres ≥ 1:40 were 28.6% and 25% for A(H1N1)pdm09, 14.3% at both timepoints for A(H3N2), and 32.1% and 25% for B(Phuket). Pre and Post-vaccination geometric mean titres(GMT) were higher by VMN than HAI for A(H1N1)pdm09 and A(H3N2), but lower for B(Phuket)(p=<0.05). Geometric mean ratios(GMR) of baseline and post-vaccination titres were similar by HAI and VMN(p > 0.05) for all components. A single seroconversion to A(H1N1) was detected by ELISA-VMN. None of patient age, lymphocyte count, days from transplant to vaccination, donor type, or graft-versus-host disease (GVHD) or immunosuppressive therapy (IST) at vaccination correlated with baseline or post-vaccination titres by either assay. This absence of seroresponse to SIIV in the first-year post HSCT highlights the need for novel immunogenic vaccination formulations and schedules in this high-risk population.

1663. Marked Improvement in Pandemic H1N1 Component Shedding and Immunogenicity in 2017–2018 Russian-Backbone Live Attenuated Influenza Vaccine (LAIV) in Gambian Children

Background

Recent observational studies in the United States have reported reduced effectiveness of the Ann Arbor-backbone live attenuated influenza vaccine (LAIV), coinciding with emergence of 2009 pandemic H1N1 (pH1N1). A recent RCT in Senegal of the Russian-backbone LAIV also showed no efficacy, with pH1N1 the predominant vaccine-matched strain circulating during the study. The reasons for this reduced effectiveness and efficacy are unclear but may involve pre-existing immunity or pH1N1 virus-specific factors. We explore these underlying reasons through an LAIV immunogenicity study in Gambian children across 2 influenza seasons.

Methods

Gambian children aged 24–59 months (n = 118) were given 2016–17 northern hemisphere Russian-backbone trivalent LAIV. Vaccine shedding, haemagglutinin inhibition (HAI) titre, influenza-specific T-cell responses, and mucosal IgA were measured using RT-PCR, HAI assay, flow cytometry, and ELISA, respectively. The following year, a further 127 children were given 2017–2018 formulation LAIV, where the pH1N1 strain was updated.

Results

In 2016–2017, significantly less pH1N1 shedding (13.6% children) was seen compared with H3N2 (45.8%) and B/Victoria (80.5%). Similarly, poor pH1N1-specific HAI (5.1% seroconversion), mucosal IgA (18.6% responders) and T-cell responses (&lt;10% responses to pH1N1 HA) were seen, whereas significantly greater responses in ≥1 immune compartments were seen to H3N2 and B/Victoria. pH1N1 shedding was not related to pre-existing immunity in 2016–2017. Vaccination with 2017–2018 LAIV showed improvement in pH1N1 shedding with no significant difference between strains: 67.7%, 63.2%, and 68.4% children shedding pH1N1, H3N2, and B/Victoria at day 2 post-LAIV (see Figure 1). This was matched by enhanced pH1N1 HA-specific T-cell responses, with 47.1% children showing a CD4+IFNg+ and 54.4% a CD4+IL2+ response (see Figure 2). HAI and mucosal IgA data for 2017–2018 are currently being generated and will be presented, as well as key interactions between the parameters measured.

Conclusion

Our data suggest that poor pH1N1 A/California strain replication in vivo may explain recent suboptimal LAIV performance and suggest that an improvement can be expected with new pH1N1 strains included in current LAIV formulations.

Disclosures

All authors: No reported disclosures.

A Randomized Trial of High-dose Influenza Vaccine in Adult Solid-Organ Transplant Recipients

Background

The annual influenza vaccine is recommended for solid-organ transplant recipients (SOTR) although studies have shown suboptimal immunogenicity. Influenza vaccine containing higher dose antigen may lead to greater immunogenicity in this population.

Method

We conducted a randomized, observer-blind trial comparing the safety and immunogenicity of high dose (HD; FluzoneHD, Sanofi) vs. standard dose (SD; Fluviral, GSK) influenza vaccine in adult SOTR. Patients were randomized 1:1 to receive the 2016–2017 influenza vaccine. Preimmunization and 4-week postimmunization sera underwent strain-specific hemagglutination inhibition assay for the three vaccine strains and an additional B strain not included in the vaccine.

Result

We randomized 172 patients and 161 (84 HD; 77 SD) were eligible for analysis. Median age was 57 years (range 18–86) and time from transplant was 38 (range 3–1402) months. Types of transplant were kidney 67 (39.0%), liver 38 (22.1%), lung 25 (14.5%), heart 23 (13.3%), and combined 19 (11.0%). Seroconversion to at least one of the three vaccine antigens (primary outcome) was present in 78.6% vs. 55.8% in HD vs. SD vaccine, respectively (P < 0.001). Seroconversion to A/H1N1, A/H3N2, and B strains were 40.5% vs. 20.5%, 57.1% vs. 32.5%, and 58.3% vs. 41.6% in HD vs. SD vaccine (P = 0.006, 0.002, 0.028, respectively). Postimmunization geometric mean titers of A/H1N1, A/H3N2, and B strains were significantly higher in the HD group 
(P = 0.007, 0.002, 0.033). Independent factors associated with seroconversion to at least one vaccine strain were the use of HD vaccine and being on mycophenolate doses less than 2 g daily (P = 0.003, 0.013, respectively). Seroconversion rate to the B strain not included in the trivalent study vaccine was also higher in the HD vaccine group (33.3% vs. 14.1%, P = 0.004). Local and systemic adverse events were similar for the two vaccines. Biopsy-proven rejection was seen in 3.4% vs. 1.2% in HD vs. SD groups, respectively (P = 0.62). Two patients in the SD vaccine group and one in the HD group developed influenza infection during the follow-up.

Conclusion

High-dose vaccine demonstrated significantly better immunogenicity than SD vaccine in adult transplant recipients and may be the preferred influenza vaccine for this population.

Disclosures

D. Kumar, Sanofi: Speaker’s Bureau, Speaker honorarium. Pfizer: Speaker’s Bureau, Speaker honorarium. GSK: Grant Investigator, Grant recipient.

Comparison of mucosal lining fluid sampling methods and influenza-specific IgA detection assays for use in human studies of influenza immunity

We need greater understanding of the mechanisms underlying protection against influenza virus to develop more effective vaccines. To do this, we need better, more reproducible methods of sampling the nasal mucosa. The aim of the current study was to compare levels of influenza virus A subtype-specific IgA collected using three different methods of nasal sampling. Samples were collected from healthy adult volunteers before and after LAIV immunization by nasal wash, flocked swabs and Synthetic Absorptive Matrix (SAM) strips. Influenza A virus subtype-specific IgA levels were measured by haemagglutinin binding ELISA or haemagglutinin binding microarray and the functional response was assessed by microneutralization. Nasosorption using SAM strips lead to the recovery of a more concentrated sample of material, with a significantly higher level of total and influenza H1-specific IgA. However, an equivalent percentage of specific IgA was observed with all sampling methods when normalized to the total IgA. Responses measured using a recently developed antibody microarray platform, which allows evaluation of binding to multiple influenza strains simultaneously with small sample volumes, were compared to ELISA. There was a good correlation between ELISA and microarray values. Material recovered from SAM strips was weakly neutralizing when used in an in vitro assay, with a modest correlation between the level of IgA measured by ELISA and neutralization, but a greater correlation between microarray-measured IgA and neutralizing activity. In conclusion we have tested three different methods of nasal sampling and show that flocked swabs and novel SAM strips are appropriate alternatives to traditional nasal washes for assessment of mucosal influenza humoral immunity.

Heterologous Immune Responses to Influenza Vaccine in Kidney Transplant Recipients

Influenza vaccine is known to have suboptimal immunogenicity in transplant recipients. Despite this, influenza vaccine may have the added benefit of inducing a cross-reactive immune response to viral strains not found in the vaccine. This is termed "heterologous immunity" and has not been assessed previously in transplant patients. Pre- and postvaccination sera from kidney transplant recipients (n = 60) immunized with the 2012-2013 adjuvanted or nonadjuvanted influenza vaccine underwent testing by hemagglutination inhibition assay for strains not present in vaccine: A/New Caledonia/20/99 (H1N1), A/Texas/50/2012 (H3N2) and B/Brisbane/60/2008. The geometric mean titer of antibody to heterologous strains increased after vaccine (H1N1: 80.0 to 136.1, p < 0.001; H3N2: 23.3 to 77.3, p < 0.001; B: 13.3 to 19.5, p < 0.001). Seroconversion rates were 16.7%, 41.7%, and 13.3%, respectively. No differences in heterologous response were seen in the adjuvanted versus nonadjuvanted groups. Patients were more likely to seroconvert for a cross-reactive antigen if they seroconverted for the specific vaccine antigen. Seroconversion to heterologous A/H3N2, for example, was 84.0% for homologous H3N2 seroconverters versus 11.4% for nonseroconverters (p < 0.001). This study provides novel evidence that transplant recipients are able to mount significant cross-protective responses to influenza vaccine that may be an additional, previously unknown benefit of immunization.

Humoral, T-cell and B-cell immune responses to seasonal influenza vaccine in solid organ transplant recipients receiving anti-T cell therapies

BACKGROUND

We analyzed the impact of the anti-T-cell agents basiliximab and antithymocyte globulins (ATG) on antibody and cell-mediated immune responses after influenza vaccination in solid-organ transplant recipients.

METHODS

71 kidney and heart transplant recipients (basiliximab [n=43] and ATG [n=28]) received the trivalent influenza vaccine. Antibody responses were measured at baseline and 6 weeks post-vaccination by hemagglutination inhibition assay; T-cell responses were measured by IFN-γ ELISpot assays and intracellular cytokine staining (ICS); and influenza-specific memory B-cell (MBC) responses were evaluated using ELISpot.

RESULTS

Median time of vaccination from transplantation was 29 months (IQR 8-73). Post-vaccination seroconversion rates were 26.8% for H1N1, 34.1% for H3N2 and 4.9% for influenza B in the basiliximab group and 35.7% for H1N1, 42.9% for H3N2 and 14.3% for influenza B in the ATG group (p=0.44, p=0.61, and p=0.21, respectively). The number of influenza-specific IFN-γ-producing cells increased significantly after vaccination (from 35 to 67.5 SFC/10(6) PBMC, p=0.0007), but no differences between treatment groups were observed (p=0.88). Median number of IgG-MBC did not increase after vaccination (H1N1, p=0.94; H3N2 p=0.34; B, p=0.79), irrespective of the type of anti-T-cell therapy.

CONCLUSIONS

After influenza vaccination, a significant increase in antibody and T-cell immune responses but not in MBC responses was observed in transplant recipients. Immune responses were not significantly different between groups that received basiliximab or ATG.

Matrix M(TM) adjuvanted virosomal H5N1 vaccine induces balanced Th1/Th2 CD4(+) T cell responses in man

T cellular responses play a significant role in mediating protective immune responses against influenza in humans. In the current study, we evaluated the ability of a candidate virosomal H5N1 vaccine adjuvanted with Matrix M(TM) to induce CD4(+) and CD8(+) T cell responses in a phase 1 clinical trial. We vaccinated 60 healthy adult volunteers (at days 0 and 21) with 30 μg haemagglutinin (HA) alone or 1.5, 7.5, or 30 μg HA formulated with Matrix M(TM). To evaluate the T cellular responses, lymphocytes were stimulated in vitro with homologous (A/Vietnam/1194/2004 [H5N1]) and heterologous H5N1 (A/Anhui/1/05 or A/Bar-headed Goose/Qinghai/1A/05) antigens. The antigen-specific cytokine responses were measured by intracellular cytokine staining and by multiplex (Luminex) assays. An increase in CD4(+) Th1 and Th2 cytokines was detected 21 days after the first vaccine dose. No increase in Th cytokine responses was observed after the second dose, although it is possible that the cytokine levels peaked earlier than sampling point at day 42. Formulation with the Matrix M(TM) adjuvant augmented both the homologous and cross-reactive cytokine response. Antigen-specific CD8(+) T cell responses were detected only in a few vaccinated individuals. The concentrations of Th1 and to a lesser extent, Th2 cytokines at 21 days post-vaccination correlated moderately with subsequent days 35 and 180 serological responses as measured by the microneutralisation, haemagglutination inhibition, and single radial hemolysis assays. Results presented here show that the virosomal H5N1 vaccine induced balanced Th1/Th2 cytokine responses and that Matrix M(TM) is a promising adjuvant for future development of candidate pandemic influenza vaccines.

Matrix M H5N1 Vaccine Induces Cross-H5 Clade Humoral Immune Responses in a Randomized Clinical Trial and Provides Protection from Highly Pathogenic Influenza Challenge in Ferrets

BACKGROUND AND METHODS

Highly pathogenic avian influenza (HPAI) viruses constitute a pandemic threat and the development of effective vaccines is a global priority. Sixty adults were recruited into a randomized clinical trial and were intramuscularly immunized with two virosomal vaccine H5N1 (NIBRG-14) doses (21 days apart) of 30 μg HA alone or 1.5, 7.5 or 30 μg HA adjuvanted with Matrix M. The kinetics and longevity of the serological responses against NIBRG-14 were determined by haemagglutination inhibition (HI), single radial haemolysis (SRH), microneutralization (MN) and ELISA assays. The cross-H5 clade responses in sera were determined by HI and the antibody-secreting (ASC) cell ELISPOT assays. The protective efficacy of the vaccine against homologous HPAI challenge was evaluated in ferrets.

RESULTS

The serological responses against the homologous and cross-reactive strains generally peaked one week after the second dose, and formulation with Matrix M augmented the responses. The NIBRG-14-specific seroprotection rates fell significantly by six months and were low against cross-reactive strains although the adjuvant appeared to prolong the longevity of the protective responses in some subjects. By 12 months post-vaccination, nearly all vaccinees had NIBRG-14-specific antibody titres below the protective thresholds. The Matrix M adjuvant was shown to greatly improve ASC and serum IgG responses following vaccination. In a HPAI ferret challenge model, the vaccine protected the animals from febrile responses, severe weight loss and local and systemic spread of the virus.

CONCLUSION

Our findings show that the Matrix M-adjuvanted virosomal H5N1 vaccine is a promising pre-pandemic vaccine candidate.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00868218.

Longevity and determinants of protective humoral immunity after pandemic influenza infection

RATIONALE

Antibodies to influenza hemagglutinin are the primary correlate of protection against infection. The strength and persistence of this immune response influences viral evolution and consequently the nature of influenza epidemics. However, the durability and immune determinants of induction of humoral immunity after primary influenza infection remain unclear.

OBJECTIVES

The spread of a novel H1N1 (A[H1N1]pdm09) virus in 2009 through an unexposed population offered a natural experiment to assess the nature and longevity of humoral immunity after a single primary influenza infection.

METHODS

We followed A(H1N1)pdm09-seronegative adults through two influenza seasons (2009-2011) as they developed A(H1N1)pdm09 influenza infection or were vaccinated. Antibodies to A(H1N1)pdm09 virus were measured by hemagglutination-inhibition assay in individuals with paired serum samples collected preinfection and postinfection or vaccination to assess durability of humoral immunity. Preexisting A(H1N1)pdm09-specific multicytokine-secreting CD4 and CD8 T cells were quantified by multiparameter flow cytometry to test the hypothesis that higher frequencies of CD4(+) T-cell responses predict stronger antibody induction after infection or vaccination.

MEASUREMENTS AND MAIN RESULTS

Antibodies induced by natural infection persisted at constant high titer for a minimum of approximately 15 months. Contrary to our initial hypothesis, the fold increase in A(H1N1)pdm09-specific antibody titer after infection was inversely correlated to the frequency of preexisting circulating A(H1N1)pdm09-specific CD4(+)IL-2(+)IFN-γ(-)TNF-α(-) T cells (r = -0.4122; P = 0.03).

CONCLUSIONS

The longevity of protective humoral immunity after influenza infection has important implications for influenza transmission dynamics and vaccination policy, and identification of its predictive cellular immune correlate could guide vaccine development and evaluation.

Incidence of influenza A(H1N1)pdm09 infection, United Kingdom, 2009-2011

We conducted a longitudinal community cohort study of healthy adults in the UK. We found significantly higher incidence of influenza A(H1N1)pdm09 infection in 2010-11 than in 2009-10, a substantial proportion of subclinical infection, and higher risk for infection during 2010-11 among persons with lower preinfection antibody titers.

International flight-related transmission of pandemic influenza A(H1N1)pdm09: an historical cohort study of the first identified cases in the United Kingdom

Background

Transporting over two billion passengers per year, global airline travel has the potential to spread emerging infectious diseases, both via transportation of infectious cases and through in-flight transmission. Current World Health Organization (WHO) guidance recommends contact tracing of passengers seated within two rows of a case of influenza during air travel.

Objectives

The objectives of this study were to describe flight-related transmission of influenza A(H1N1)pdm09 during a commercial flight carrying the first cases reported in the United Kingdom and to test the specific hypothesis that passengers seated within two rows of an infectious case are at greater risk of infection.

Methods

An historical cohort study, supplemented by contact tracing, enhanced surveillance data and laboratory testing, was used to establish a case status for passengers on board the flight.

Results

Data were available for 239 of 278 (86·0%) of passengers on the flight, of whom six were considered infectious in-flight and one immune. The attack rate (AR) was 10 of 232 (4·3%; 95% CI 1·7–6·9%). There was no evidence that the AR for those seated within two rows of an infectious case was different from those who were not (relative risk 0·9; 95% CI 0·2–3·1; P = 1·00). Laboratory testing using PCR and/or serology, available for 118 of 239 (49·4%) of the passengers, was largely consistent with clinically defined case status.

Conclusions

This study of A(H1N1)pdm09 does not support current WHO guidance regarding the contact tracing of passengers seated within two rows of an infectious case of influenza during air travel.

Administration of AS03B-adjuvanted A(H1N1)pdm09 vaccine in children aged <3 years enhances antibody response to H3 and B viruses following a single dose of trivalent vaccine one year later

BACKGROUND

We report on a follow-up clinical and serological investigation of 274 children who received seasonal influenza vaccine (trivalent inactivated vaccine [TIV]) 1 year after receipt of either AS03(B)-adjuvanted subunit or whole virus monovalent A(H1N1)pdm09 vaccine and describe the antibody responses to the H3N2 A/Perth/16/2009 and B/Brisbane/60/2008 components of TIV.

METHODS

Vaccine responses were analyzed using hemagglutination inhibition (HAI) assays. In children aged <3 years, previous receipt of adjuvanted vaccine resulted in higher HAI antibody responses to H3N2 and B strains compared with nonadjuvanted vaccine (fold change 16.8 vs 4.3 for H3N2 and 7.0 vs 1.6 for B). In children aged >3 years, responses to the H3 and B components of TIV were similar between vaccine groups. Sera taken before and after the pandemic vaccine were also analyzed by HAI using A/Perth/16/2009 virus. This analysis showed that 11.1% of children receiving the AS03(B)-adjuvanted vaccine but only 1.4% in the nonadjuvanted group had a 4-fold rise to A/Perth/16/2009.

CONCLUSION

AS03B-adjuvanted A(H1N1)pdm09 influenza vaccine generates a cross-reactive antibody response to H3N2 in children and enhances responses to heterologous subtypes in children aged <3 years 1 year later.

Population susceptibility to North American and Eurasian swine influenza viruses in England, at three time points between 2004 and 2011

Age-stratified sera collected in 2004, 2008 and 2010 in England were evaluated for antibody to swine influenza A(H3N2) and A(H1N1) viruses from the United States or Europe as a measure of population susceptibility to the emergence of novel viruses. Children under 11 years of age had little or no measurable antibody to recent swine H3N2 viruses despite their high levels of antibody to recent H3N2 seasonal human strains. Adolescents and young adults (born 1968–1999) had higher antibody levels to swine H3N2 viruses. Antibody levels to swine H3N2 influenza show little correlation with exposure to recent seasonal H3N2 (A/Perth/16/2009) strains, but with antibody to older H3N2 strains represented by A/Wuhan/359/1995. Children had the highest seropositivity to influenza A(H1N1)pdm09 virus, and young adults had the lowest antibody levels to A/Perth/16/2009. No age group showed substantial antibody levels to A/Aragon/RR3218/2008, a European swine H1N1 virus belonging to the Eurasian lineage. After vaccination with contemporary trivalent vaccine we observed evidence of boosted reactivity to swine H3N2 viruses in children and adults, while only a limited boosting effect on antibody levels to A/Aragon/RR3218/2008 was observed in both groups. Overall, our results suggest that different vaccination strategies may be necessary according to age if swine viruses emerge as a significant pandemic threat.