Shared neutrophil and T cell dysfunction is accompanied by a distinct interferon signature during severe febrile illnesses in children.

Severe febrile illnesses in children encompass life-threatening organ dysfunction caused by diverse pathogens and other severe inflammatory syndromes. A comparative approach to these illnesses may identify shared and distinct features of host immune dysfunction amenable to immunomodulation. Here, using immunophenotyping with mass cytometry and cell stimulation experiments, we illustrate trajectories of immune dysfunction in 74 children with multi-system inflammatory syndrome in children (MIS-C) associated with SARS-CoV-2, 30 with bacterial infection, 16 with viral infection, 8 with Kawasaki disease, and 42 controls. We explore these findings in a secondary cohort of 500 children with these illnesses and 134 controls. We show that neutrophil activation and apoptosis are prominent in multi-system inflammatory syndrome, and that this is partially shared with bacterial infection. We show that memory T cells from patients with multi-system inflammatory syndrome and bacterial infection are exhausted. In contrast, we show viral infection to be characterized by a distinct signature of decreased interferon signaling and lower interferon receptor gene expression. Improved understanding of immune dysfunction may improve approaches to immunomodulator therapy in severe febrile illnesses in children.

Clinical Management of Hospitalized Patients With High-Consequence Infectious Diseases in England.

Infectious disease physicians in England have been diagnosing and managing occasional cases of viral hemorrhagic fever since 1971, including the United Kingdom's first case of Ebola virus disease in 1976. Specialist isolation facilities to provide safe and effective care have been present since that time. Following the emergence of Middle East respiratory syndrome (MERS) in 2012, and the avian influenza A (H7N9) outbreak in 2013, and the 2014-2016 Ebola virus disease outbreak in West Africa, clinical and public health preparedness and response pathways in England have been strengthened for these types of diseases, now called high-consequence infectious diseases (HCIDs). The HCID program, led by NHS England and Public Health England between 2016 and 2018, helped to deliver these enhancements, which have since been used on multiple occasions for new UK cases and outbreaks of MERS, mpox, avian influenza, and Lassa fever. Additionally, HCID pathways were activated for COVID-19 during the first 3 months of 2020, before the pandemic had been declared and little was known about COVID-19 but HCID status had been assigned temporarily to COVID-19 as a precaution. The HCID program also led to the commissioning of a network of new airborne HCID treatment centers in England, to supplement the existing network of contact HCID treatment centers, which includes the United Kingdom's only 2 high-level isolation units. In this case study, the authors describe the airborne and contact HCID treatment center networks in England, including their formation and structures, their approach to safe and effective clinical management of patients with HCIDs in the United Kingdom, and challenges they may face going forward.

The impact of the COVID-19 pandemic on UK parents' attitudes towards routine childhood vaccines: A mixed-methods study.

BACKGROUND: COVID-19 vaccines were key to controlling the pandemic and vaccination has been discussed extensively by the media and the public since 2020. We aimed to explore parents' attitudes towards routine childhood vaccination since COVID-19 and how the pandemic impacted their experiences of getting their child vaccinated. METHODS: We used a mixed-methods approach-involving a questionnaire survey followed by focus groups. We partnered with The Mosaic Community Trust, an ethnic minority women's group based in a deprived area of North-West London, United Kingdom (UK) with historically low childhood vaccine uptake. Descriptive findings from the questionnaires were reported and chi-square analyses performed to examine differences by ethnicity. Thematic analysis of the free-text questionnaire responses and focus groups was undertaken, guided by the COM-B model of Capability, Opportunity, and Motivation. RESULTS: Between Jun-Oct 2022, 518 parents completed the questionnaire (25% from ethnic minorities). Between March-May 2023 we held four focus groups with 22 parents (45% from ethnic minorities). Most parents (>90%) thought routine childhood vaccines for children were important. Over a third (38%) of all parents reported having more questions about childhood vaccines since COVID-19, though among parents belonging to an ethnicity group other than white, 59% said they had more questions compared to those of any white ethnicity group (30%, (p = <0.0001)). Difficulties accessing vaccine appointments were commoner reasons for children's vaccinations being delayed than parents increased concerns about vaccines. Since COVID-19 some parents felt vaccinations were even more important, and a very small minority felt the pandemic had made them mistrust vaccinations. CONCLUSION: Following COVID-19, we found parents remain confident in childhood vaccines. However, some parents, particularly from ethnic minority groups may have more questions about childhood vaccines than pre-pandemic. Post COVID-19, to address declining vaccine uptake, parents need easy access to healthcare professionals to answer questions about childhood vaccinations.

Using a novel methodology to map Post-COVID services for children and young people in England: a web-based systematic search.

BACKGROUND: Post-COVID Condition (PCC), also known as 'Long COVID,' refers to persistent symptoms following a coronavirus 2 (SARS-CoV-2) infection. The prevalence of PCC in children and adolescents varies, impacting multiple body systems and affecting daily functioning. Specialised paediatric hubs were established in England to address the needs of young individuals with PCC. Additional local services also emerged, yet patients report challenges accessing services. To better understand the landscape of paediatric PCC services, we used a novel methodology using a web-based systematic search. METHODS: A web-based search was conducted in July 2023 using DEVONagent Pro. Search terms related to Long COVID and Pediatrics in England. Eligible sources providing information on PCC services for children and young people were included. A supplementary manual search and NHS England Post-COVID Network were also consulted. Data extraction included service location, characteristics, and referral pathways. Population estimates were derived from UK Census data. RESULTS: Among 342 identified records, 27 services met eligibility criteria, distributed unevenly across regions. Specialised hubs covered 13 locations, while additional services were concentrated in the South of England and London. Services varied in team composition, age range treated, and support offered. A lack of standardised approaches for paediatric PCC was evident. DISCUSSION: We used a novel methodology for systematically mapping online resources, providing valuable insights into service accessibility and aiding the identification of potential gaps. We observed geographical disparities in access to paediatric PCC services and the absence of standardised approaches in managing symptoms. Given the challenges faced by young individuals seeking support for their PCC the need for equitable and standardised care became apparent. The study contributes to closing the research-practice gap and calls for further research to identify effective treatments for paediatric PCC, acknowledging the diversity of reported symptoms and the importance of tailored approaches.

Epidemiology and Management of Pediatric Group A Streptococcal Pneumonia With Parapneumonic Effusion: An Observational Study.

BACKGROUND: During autumn/winter 2022, UK pediatricians reported an unseasonal increase in invasive group A streptococcal infections; a striking proportion presenting with pneumonia with parapneumonic effusion. METHODS: Clinicians across the United Kingdom were requested to submit pseudonymized clinical data using a standardized report form for children (<16 years) admitted between September 30, 2022 and February 17, 2023, with microbiologically confirmed group A streptococcal pneumonia with parapneumonic effusion. RESULTS: From 185 cases submitted, the median patient age was 4.4 years, and 163 (88.1%) were previously healthy. Respiratory viral coinfection was detected on admission for 101/153 (66.0%) children using extended respiratory pathogen polymerase chain reaction panel. Molecular testing was the primary method of detecting group A streptococcus on pleural fluid (86/171; 50.3% samples). Primary surgical management was undertaken in 171 (92.4%) children; 153/171 (89.4%) had pleural drain inserted (96 with fibrinolytic agent), 14/171 (8.2%) had video-assisted thoracoscopic surgery. Fever duration after admission was prolonged (median, 12 days; interquartile range, 9-16). Intravenous antibiotic courses varied in length (median, 14 days; interquartile range, 12-21), with many children receiving multiple broad-spectrum antibiotics, although evidence for additional bacterial infection was limited. CONCLUSIONS: Most cases occurred with viral coinfection, a previously well-recognized risk with influenza and varicella zoster, highlighting the need to ensure routine vaccination coverage and progress on vaccines for other common viruses (eg, respiratory syncytial virus, human metapneumovirus) and for group A streptococcus. Molecular testing is valuable to detect viral coinfection and confirm invasive group A streptococcal diagnosis, expediting the incorporation of cases into national reporting systems. Range and duration of intravenous antibiotics administered demonstrated the need for research on the optimal duration of antimicrobials and improved stewardship.

A Multidisciplinary Approach: Management and Rehabilitation of Children With Pediatric Post-COVID-19 Condition.

Post-COVID-19 condition in children is a still largely unknown syndrome with a diverse pattern of symptoms, which can have a major impact on daily life. Currently, there are no evidence-based proven treatments, and the focus is on symptom management and recovery of daily functioning. A multidisciplinary, tailored approach is recommended, with attention to energy management and activity building, where the main goal should be a return to baseline levels of cognitive, physical and social activity.

Post-Covid-19 condition (Long Covid) in children and young people 12 months after infection or reinfection with the Omicron variant: a prospective observational study.

Our previous study in children and young people (CYP) at 3- and 6-months post-infection showed that 12-16% of those infected with the Omicron (B.1.1.529) variant of SARS-CoV-2 met the research definition of Long Covid, with no differences between first-positive and reinfected CYP. The primary objective of the current study is to explore the impact of the Omicron variant of SARS-CoV-2 infection on young people 12 months post infection. 345 CYP aged 11-17 years with a first laboratory-confirmed infection with the Omicron variant and 360 CYP reinfected with the Omicron variant completed an online questionnaire assessing demographics, symptoms, and their impact shortly after testing and again at 3-, 6-and 12-months post-testing. Vaccination status was determined from information held at UKHSA. Comparisons between groups were made using chi-squared, Mann-Whitney U, and Kruskal-Wallis tests. The most common symptoms in first-positive and reinfected CYP 12-months post-testing were tiredness (35.7 and 33.6% respectively) and sleeping difficulties (27.5 and 28.3% respectively). Symptom profiles, severity and impact were similar in the two infection status groups. Overall, by 12-months, 17.4% of first-positives and 21.9% of reinfected CYP fulfilled the research consensus Long Covid definition (p = 0.13). 12-months post Omicron infection, there is little difference between first-positive and reinfected CYP with respect to symptom profiles and impact. Clinicians may not therefore need to consider number of infections and type of variant when developing treatment plans. Further studies are needed to assess causality of reported symptoms up to 12-months after SARS-CoV-2 infection.

A review of post COVID syndrome pathophysiology, clinical presentation and management in children and young people.

Post Covid Syndrome (PCS) is a complex multi-system disorder with a spectrum of presentations. Severity ranges from mild to very severe with variable duration of illness and recovery. This paper discusses the difficulties defining and describing PCS. We review the current understanding of PCS, epidemiology, and predisposing factors. We consider potential mechanisms including viral persistence, clotting dysfunction and immunity. We review presentation and diagnosis and finally consider management strategies including addressing symptom burden, rehabilitation, and novel therapies.

Paediatric, maternal, and congenital mpox: a systematic review and meta-analysis.

BACKGROUND: Although mpox has been detected in paediatric populations in central and west Africa for decades, evidence synthesis on paediatric, maternal, and congenital mpox, and the use of vaccines and therapeutics in these groups, is lacking. A systematic review is therefore indicated to set the research agenda. METHODS: We conducted a systematic review and meta-analysis, searching articles in Embase, Global Health, MEDLINE, CINAHL, Web of Science, Scopus, SciELO, and WHO databases from inception to April 17, 2023. We included studies reporting primary data on at least one case of confirmed, suspected, or probable paediatric, maternal, or congenital mpox in humans or the use of third-generation smallpox or mpox vaccines, targeted antivirals, or immune therapies in at least one case in our population of interest. We included clinical trials and observational studies in humans and excluded reviews, commentaries, and grey literature. A pooled estimate of the paediatric case fatality ratio was obtained using random-effects meta-analysis. This study is registered with PROSPERO (CRD420223336648). FINDINGS: Of the 61 studies, 53 reported paediatric outcomes (n=2123 cases), seven reported maternal or congenital outcomes (n=32 cases), two reported vaccine safety (n=28 recipients), and three reported transmission during breastfeeding (n=4 cases). While a subset of seven observational studies (21 children and 12 pregnant individuals) reported uneventful treatment with tecovirimat, there were no randomised trials reporting safety or efficacy for any therapeutic agent. Among children, the commonest clinical features included rash (86 [100%] of 86), fever (63 [73%] of 86), and lymphadenopathy (40 [47%] of 86). Among pregnant individuals, rash was reported in 23 (100%) of 23; fever and lymphadenopathy were less common (six [26%] and three [13%] of 23, respectively). Most paediatric complications (12 [60%] of 20) arose from secondary bacterial infections. The pooled paediatric case fatality ratio was 11% (95% CI 4-20), I2=75%. Data from 12 pregnancies showed half resulted in fetal death. Research on vaccine and immune globulin safety remains scarce for children and absent for pregnant individuals. INTERPRETATION: Our review highlights critical knowledge gaps in the epidemiology, prevention, and treatment of mpox in children and pregnant individuals, especially those residing in endemic countries. Increased funding, international collaboration, and equitable research is needed to inform mpox control strategies tailored for at-risk communities in endemic countries. FUNDING: None. TRANSLATIONS: For the French, Spanish and Portuguese translations of the abstract see Supplementary Materials section.

Fifteen-minute consultation: Managing post-COVID-19 syndrome (long COVID) in children and young people.

Post-COVID-19 syndrome is a new condition that can have a major impact on the physical and mental well-being of children and young people, affecting their ability to access activities including education. Paediatricians and general practitioners need to be able to assess and manage patients with this condition; making the diagnosis, excluding serious pathology, managing comorbidities and accessing appropriate management are crucial. This 15 minute consultation presents an approach to history taking, examination, investigations, management principles and referrals.

Children and Young People with Long COVID-Comparing Those Seen in Post-COVID Services with a Non-Hospitalised National Cohort: A Descriptive Study.

BACKGROUND: Post-COVID services have been set up in England to treat children with ongoing symptoms of Long COVID. To date, the characteristics of children seeking treatment from these services has not been described. PURPOSE: (1) to describe the characteristics of children aged 11-17 referred to the Pan-London Post-COVID service and (2) to compare characteristics of these children with those taking part in the United Kingdom's largest research study of Long COVID in children (CLoCk). DESIGN: Data from 95 children seeking treatment from the Post-COVID service between May 2021 and August 2022 were included in the study. Their demographic characteristics, symptom burden and the impact of infection are described and compared to children from CLoCk. RESULTS: A high proportion of children from the Post-COVID service and CLoCk reported experiencing health problems prior to the pandemic. Almost all Post-COVID service children met the research Delphi definition of Long COVID (94.6%), having multiple symptoms that impacted their lives. Symptoms were notably more severe than the participants in CLoCk. CONCLUSIONS: This study describes the characteristics of children seeking treatment for Long COVID compared to those identified in the largest longitudinal observational study to date. Post-COVID service children have more symptoms and are more severely affected by their symptoms following infection with COVID-19 than children in the CLoCk study. Research to understand predisposing factors for severity and prognostic indicators is essential to prevent this debilitating condition. Evaluation of short- and long-term outcomes of interventions by clinical services can help direct future therapy for this group.

Neuroinflammation, autoinflammation, splenomegaly and anemia caused by bi-allelic mutations in IRAK4.

We describe a novel, severe autoinflammatory syndrome characterized by neuroinflammation, systemic autoinflammation, splenomegaly, and anemia (NASA) caused by bi-allelic mutations in IRAK4. IRAK-4 is a serine/threonine kinase with a pivotal role in innate immune signaling from toll-like receptors and production of pro-inflammatory cytokines. In humans, bi-allelic mutations in IRAK4 result in IRAK-4 deficiency and increased susceptibility to pyogenic bacterial infections, but autoinflammation has never been described. We describe 5 affected patients from 2 unrelated families with compound heterozygous mutations in IRAK4 (c.C877T (p.Q293*)/c.G958T (p.D320Y); and c.A86C (p.Q29P)/c.161 + 1G>A) resulting in severe systemic autoinflammation, massive splenomegaly and severe transfusion dependent anemia and, in 3/5 cases, severe neuroinflammation and seizures. IRAK-4 protein expression was reduced in peripheral blood mononuclear cells (PBMC) in affected patients. Immunological analysis demonstrated elevated serum tumor necrosis factor (TNF), interleukin (IL) 1 beta (IL-1ß), IL-6, IL-8, interferon α2a (IFN-α2a), and interferon ß (IFN-ß); and elevated cerebrospinal fluid (CSF) IL-6 without elevation of CSF IFN-α despite perturbed interferon gene signature. Mutations were located within the death domain (DD; p.Q29P and splice site mutation c.161 + 1G>A) and kinase domain (p.Q293*/p.D320Y) of IRAK-4. Structure-based modeling of the DD mutation p.Q29P showed alteration in the alignment of a loop within the DD with loss of contact distance and hydrogen bond interactions with IRAK-1/2 within the myddosome complex. The kinase domain mutation p.D320Y was predicted to stabilize interactions within the kinase active site. While precise mechanisms of autoinflammation in NASA remain uncertain, we speculate that loss of negative regulation of IRAK-4 and IRAK-1; dysregulation of myddosome assembly and disassembly; or kinase active site instability may drive dysregulated IL-6 and TNF production. Blockade of IL-6 resulted in immediate and complete amelioration of systemic autoinflammation and anemia in all 5 patients treated; however, neuroinflammation has, so far proven recalcitrant to IL-6 blockade and the janus kinase (JAK) inhibitor baricitinib, likely due to lack of central nervous system penetration of both drugs. We therefore highlight that bi-allelic mutation in IRAK4 may be associated with a severe and complex autoinflammatory and neuroinflammatory phenotype that we have called NASA (neuroinflammation, autoinflammation, splenomegaly and anemia), in addition to immunodeficiency in humans.

Pediatric Hospitalizations and ICU Admissions Due to COVID-19 and Pediatric Inflammatory Multisystem Syndrome Temporally Associated With SARS-CoV-2 in England.

Importance: Investigating how the risk of serious illness after SARS-CoV-2 infection in children and adolescents has changed as new variants have emerged is essential to inform public health interventions and clinical guidance. Objective: To examine risk factors associated with hospitalization for COVID-19 or pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) among children and adolescents during the first 2 years of the COVID-19 pandemic and change in risk factors over time. Design, Setting, and Participants: This population-level analysis of hospitalizations after SARS-CoV-2 infection in England among children and adolescents aged 0 to 17 years was conducted from February 1, 2020, to January 31, 2022. National data on hospital activity were linked with data on SARS-CoV-2 testing, SARS-CoV-2 vaccination, pediatric intensive care unit (PICU) admissions, and mortality. Children and adolescents hospitalized with COVID-19 or PIMS-TS during this time were included. Maternal, elective, and injury-related hospitalizations were excluded. Exposures: Previous medical comorbidities, sociodemographic factors, and timing of hospitalization when different SARS-CoV-2 variants (ie, wild type, Alpha, Delta, and Omicron) were dominant in England. Main Outcomes: PICU admission and death within 28 days of hospitalization with COVID-19 or PIMS-TS. Results: A total of 10 540 hospitalizations due to COVID-19 and 997 due to PIMS-TS were identified within 1 125 010 emergency hospitalizations for other causes. The number of hospitalizations due to COVID-19 and PIMS-TS per new SARS-CoV-2 infections in England declined during the second year of the COVID-19 pandemic. Among 10 540 hospitalized children and adolescents, 448 (4.3%) required PICU admission due to COVID-19, declining from 162 of 1635 (9.9%) with wild type, 98 of 1616 (6.1%) with Alpha, and 129 of 3789 (3.4%) with Delta to 59 of 3500 (1.7%) with Omicron. Forty-eight children and adolescents died within 28 days of hospitalization due to COVID-19, and no children died of PIMS-TS (PIMS-S data were limited to November 2020 onward). Risk of severe COVID-19 in children and adolescents was associated with medical comorbidities and neurodisability regardless of SARS-CoV-2 variant. Results were similar when children and adolescents with prior SARS-CoV-2 exposure or vaccination were excluded. Conclusions: In this study of data across the first 2 years of the COVID-19 pandemic, risk of severe disease from SARS-CoV-2 infection in children and adolescents in England remained low. Children and adolescents with multiple medical problems, particularly neurodisability, were at increased risk and should be central to public health measures as further variants emerge.

SARS-CoV-2 infection and pulmonary tuberculosis in children and adolescents: a case-control study.

BACKGROUND: The Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) pandemic has had an impact on the global tuberculosis (TB) epidemic but evidence on the possible interaction between SARS-CoV-2 and TB, especially in children and adolescents, remains limited. We aimed to evaluate the relationship between previous infection with SARS-CoV-2 and the risk of TB in children and adolescents. METHODS: An unmatched case-control study was conducted using SARS-CoV-2 unvaccinated children and adolescents recruited into two observational TB studies (Teen TB and Umoya), between November 2020 and November 2021, in Cape Town, South Africa. Sixty-four individuals with pulmonary TB (aged < 20 years) and 99 individuals without pulmonary TB (aged < 20 years) were included. Demographics and clinical data were obtained. Serum samples collected at enrolment underwent quantitative SARS-CoV-2 anti-spike immunoglobulin G (IgG) testing using the Abbott SARS-CoV-2 IgG II Quant assay. Odds ratios (ORs) for TB were estimated using unconditional logistic regression. RESULTS: There was no statistically significant difference in the odds of having pulmonary TB between those who were SARS-CoV-2 IgG seropositive and those who were seronegative (adjusted OR 0.51; 95% CI: 0.23-1.11; n = 163; p = 0.09). Of those with positive SARS-CoV-2 serology indicating prior infection, baseline IgG titres were higher in individuals with TB compared to those without TB (p = 0.04) and individuals with IgG titres in the highest tertile were more likely to have pulmonary TB compared to those with IgG levels in the lowest tertile (OR: 4.00; 95%CI: 1.13- 14.21; p = 0.03). CONCLUSIONS: Our study did not find convincing evidence that SARS-CoV-2 seropositivity was associated with subsequent pulmonary TB disease; however, the association between magnitude of SARS-CoV-2 IgG response and pulmonary TB warrants further investigation. Future prospective studies, evaluating the effects of sex, age and puberty on host immune responses to M. tuberculosis and SARS-CoV-2, will also provide more clarity on the interplay between these two infections.

Early evaluation of the safety, reactogenicity, and immune response after a single dose of modified vaccinia Ankara-Bavaria Nordic vaccine against mpox in children: a national outbreak response.

BACKGROUND: In response to a national mpox (formerly known as monkeypox) outbreak in England, children exposed to a confirmed mpox case were offered modified vaccinia Ankara-Bavaria Nordic (MVA-BN), a third-generation smallpox vaccine, for post-exposure prophylaxis. We aimed to assess the safety and reactogenicity and humoral and cellular immune response, following the first reported use of MVA-BN in children. METHODS: This is an assessment of children receiving MVA-BN for post-exposure prophylaxis in response to a national mpox outbreak in England. All children receiving MVA-BN were asked to complete a post-vaccination questionnaire online and provide a blood sample 1 month and 3 months after vaccination. Outcome measures for the questionnaire included reactogenicity and adverse events after vaccination. Blood samples were tested for humoural, cellular, and cytokine responses and compared with unvaccinated paediatric controls who had never been exposed to mpox. FINDINGS: Between June 1 and Nov 30, 2022, 87 children had one MVA-BN dose and none developed any serious adverse events or developed mpox disease after vaccination. Post-vaccination reactogenicity questionnaires were completed by 45 (52%) of 87 children. Their median age was 5 years (IQR 5-9), 25 (56%) of 45 were male, and 22 (49%) of 45 were White. 16 (36%) reported no symptoms, 18 (40%) reported local reaction only, and 11 (24%) reported systemic symptoms with or without local reactions. Seven (8%) of 87 children provided a first blood sample a median of 6 weeks (IQR 6·0-6·5) after vaccination and five (6%) provided a second blood sample at a median of 15 weeks (14-15). All children had poxvirus IgG antibodies with titres well above the assay cutoff of OD450nm 0·1926 with mean absorbances of 1·380 at six weeks and 0·9826 at 15 weeks post-vaccination. Assessment of reactivity to 27 recombinant vaccina virus and monkeypox virus proteins showed humoral antigen recognition, primarily to monkeypox virus antigens B6, B2, and vaccina virus antigen B5, with waning of humoral responses observed between the two timepoints. All children had a robust T-cell response to whole modified vaccinia Ankara virus and a select pool of conserved pan-Poxviridae peptides. A balanced CD4+ and CD8+ T-cell response was evident at 6 weeks, which was retained at 15 weeks after vaccination. INTERPRETATION: A single dose of MVA-BN for post-exposure prophylaxis was well-tolerated in children and induced robust antibody and cellular immune responses up to 15 weeks after vaccination. Larger studies are needed to fully assess the safety, immunogenicity, and effectiveness of MVA-BN in children. Our findings, however, support its on-going use to prevent mpox in children as part of an emergency public health response. FUNDING: UK Health Security Agency.