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Bueno de Mesquita PJ, Nguyen‐Van‐Tam J, Killingley B, Enstone J, Lambkin‐Williams R, Gilbert AS, Mann A, Forni J, Yan J, Pantelic J, Grantham ML, Milton DK. Influenza A (H3) illness and viral aerosol shedding from symptomatic naturally infected and experimentally infected cases. Influenza Other Respir Viruses 2021; 15:154-163. [PMID: 32705798 PMCID: PMC7767952 DOI: 10.1111/irv.12790] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND It has long been known that nasal inoculation with influenza A virus produces asymptomatic to febrile infections. Uncertainty persists about whether these infections are sufficiently similar to natural infections for studying human-to-human transmission. METHODS We compared influenza A viral aerosol shedding from volunteers nasally inoculated with A/Wisconsin/2005 (H3N2) and college community adults naturally infected with influenza A/H3N2 (2012-2013), selected for influenza-like illness with objectively measured fever or a positive Quidel QuickVue A&B test. Propensity scores were used to control for differences in symptom presentation observed between experimentally and naturally infected groups. RESULTS Eleven (28%) experimental and 71 (86%) natural cases shed into fine particle aerosols (P < .001). The geometric mean (geometric standard deviation) for viral positive fine aerosol samples from experimental and natural cases was 5.1E + 3 (4.72) and 3.9E + 4 (15.12) RNA copies/half hour, respectively. The 95th percentile shedding rate was 2.4 log10 greater for naturally infected cases (1.4E + 07 vs 7.4E + 04). Certain influenza-like illness-related symptoms were associated with viral aerosol shedding. The almost complete lack of symptom severity distributional overlap between groups did not support propensity score-adjusted shedding comparisons. CONCLUSIONS Due to selection bias, the natural and experimental infections had limited symptom severity distributional overlap precluding valid, propensity score-adjusted comparison. Relative to the symptomatic naturally infected cases, where high aerosol shedders were found, experimental cases did not produce high aerosol shedders. Studying the frequency of aerosol shedding at the highest observed levels in natural infections without selection on symptoms or fever would support helpful comparisons.
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Affiliation(s)
- Paul Jacob Bueno de Mesquita
- University of Maryland School of Public HealthMaryland Institute for Applied Environmental HealthCollege ParkMDUSA
| | - Jonathan Nguyen‐Van‐Tam
- Division of Epidemiology and Public HeathHealth Protection and Influenza Research GroupUniversity of Nottingham School of MedicineNottinghamUK
| | - Ben Killingley
- Division of Epidemiology and Public HeathHealth Protection and Influenza Research GroupUniversity of Nottingham School of MedicineNottinghamUK
| | - Joanne Enstone
- Division of Epidemiology and Public HeathHealth Protection and Influenza Research GroupUniversity of Nottingham School of MedicineNottinghamUK
| | | | | | | | - John Forni
- hVIVOLondonUK
- Present address:
Department of Acute and Specialty CareMSDLondonUK
| | - Jing Yan
- University of Maryland School of Public HealthMaryland Institute for Applied Environmental HealthCollege ParkMDUSA
| | - Jovan Pantelic
- University of Maryland School of Public HealthMaryland Institute for Applied Environmental HealthCollege ParkMDUSA
- Present address:
Center for the Built EnvironmentUniversity of CaliforniaBerkeleyCAUSA
| | - Michael L. Grantham
- University of Maryland School of Public HealthMaryland Institute for Applied Environmental HealthCollege ParkMDUSA
- Present address:
Missouri Western State UniversitySt. JosephMOUSA
| | - Donald K. Milton
- University of Maryland School of Public HealthMaryland Institute for Applied Environmental HealthCollege ParkMDUSA
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Nguyen-Van-Tam JS, Killingley B, Enstone J, Hewitt M, Pantelic J, Grantham ML, Bueno de Mesquita PJ, Lambkin-Williams R, Gilbert A, Mann A, Forni J, Noakes CJ, Levine MZ, Berman L, Lindstrom S, Cauchemez S, Bischoff W, Tellier R, Milton DK. Minimal transmission in an influenza A (H3N2) human challenge-transmission model within a controlled exposure environment. PLoS Pathog 2020; 16:e1008704. [PMID: 32658939 PMCID: PMC7390452 DOI: 10.1371/journal.ppat.1008704] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 07/29/2020] [Accepted: 06/14/2020] [Indexed: 12/22/2022] Open
Abstract
Uncertainty about the importance of influenza transmission by airborne droplet nuclei generates controversy for infection control. Human challenge-transmission studies have been supported as the most promising approach to fill this knowledge gap. Healthy, seronegative volunteer ‘Donors’ (n = 52) were randomly selected for intranasal challenge with influenza A/Wisconsin/67/2005 (H3N2). ‘Recipients’ randomized to Intervention (IR, n = 40) or Control (CR, n = 35) groups were exposed to Donors for four days. IRs wore face shields and hand sanitized frequently to limit large droplet and contact transmission. One transmitted infection was confirmed by serology in a CR, yielding a secondary attack rate of 2.9% among CR, 0% in IR (p = 0.47 for group difference), and 1.3% overall, significantly less than 16% (p<0.001) expected based on a proof-of-concept study secondary attack rate and considering that there were twice as many Donors and days of exposure. The main difference between these studies was mechanical building ventilation in the follow-on study, suggesting a possible role for aerosols. Understanding the relative importance of influenza modes of transmission informs strategic use of preventive measures to reduce influenza risk in high-risk settings such as hospitals and is important for pandemic preparedness. Given the increasing evidence from epidemiological modelling, exhaled viral aerosol, and aerobiological survival studies supporting a role for airborne transmission and the potential benefit of respirators (and other precautions designed to prevent inhalation of aerosols) versus surgical masks (mainly effective for reducing exposure to large droplets) to protect healthcare workers, more studies are needed to evaluate the extent of risk posed airborne versus contact and large droplet spray transmission modes. New human challenge-transmission studies should be carefully designed to overcome limitations encountered in the current study. The low secondary attack rate reported herein also suggests that the current challenge-transmission model may no longer be a more promising approach to resolving questions about transmission modes than community-based studies employing environmental monitoring and newer, state-of-the-art deep sequencing-based molecular epidemiological methods.
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Affiliation(s)
- Jonathan S. Nguyen-Van-Tam
- Health Protection and Influenza Research Group, Division of Epidemiology and Public Heath, University of Nottingham School of Medicine, Nottingham, United Kingdom
| | - Ben Killingley
- Health Protection and Influenza Research Group, Division of Epidemiology and Public Heath, University of Nottingham School of Medicine, Nottingham, United Kingdom
- * E-mail:
| | - Joanne Enstone
- Health Protection and Influenza Research Group, Division of Epidemiology and Public Heath, University of Nottingham School of Medicine, Nottingham, United Kingdom
| | - Michael Hewitt
- Health Protection and Influenza Research Group, Division of Epidemiology and Public Heath, University of Nottingham School of Medicine, Nottingham, United Kingdom
| | - Jovan Pantelic
- University of Maryland School of Public Health, Maryland Institute for Applied Environmental Health, College Park, Maryland, United States of America
| | - Michael L. Grantham
- University of Maryland School of Public Health, Maryland Institute for Applied Environmental Health, College Park, Maryland, United States of America
| | - P. Jacob Bueno de Mesquita
- University of Maryland School of Public Health, Maryland Institute for Applied Environmental Health, College Park, Maryland, United States of America
| | | | | | | | | | | | - Min Z. Levine
- Centers for Disease Control and Prevention, Influenza Division, Atlanta, Georgia, United States of America
| | - LaShondra Berman
- Centers for Disease Control and Prevention, Influenza Division, Atlanta, Georgia, United States of America
| | - Stephen Lindstrom
- Centers for Disease Control and Prevention, Influenza Division, Atlanta, Georgia, United States of America
| | - Simon Cauchemez
- Imperial College London, MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, London, United Kingdom
| | - Werner Bischoff
- Wake Forest School of Medicine, Winston-Salem, North Carolina, United States of America
| | | | - Donald K. Milton
- University of Maryland School of Public Health, Maryland Institute for Applied Environmental Health, College Park, Maryland, United States of America
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Anderson S, Garnett GP, Enstone J, Hallett TB. The importance of local epidemic conditions in monitoring progress towards HIV epidemic control in Kenya: a modelling study. J Int AIDS Soc 2018; 21:e25203. [PMID: 30485720 PMCID: PMC6260921 DOI: 10.1002/jia2.25203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 10/02/2018] [Indexed: 11/06/2022] Open
Abstract
INTRODUCTION Setting and monitoring progress towards targets for HIV control is critical in ensuring responsive programmes. Here, we explore how to apply targets for reduction in HIV incidence to local settings and which indicators give the strongest signal of a change in incidence in the population and are therefore most important to monitor. METHODS We use location-specific HIV transmission models, tailored to the epidemics in the counties and major cities in Kenya, to project a wide range of plausible future epidemic trajectories through varying behaviours, treatment coverage and prevention interventions. We look at the change in incidence across modelled scenarios in each location between 2015 and 2030 to inform local target setting. We also simulate the measurement of a library of potential indicators and assess which are most strongly associated with a change in incidence. RESULTS Considerable variation was observed in the trajectory of the local epidemics under the plausible scenarios defined (only 10 of 48 locations saw a median reduction in incidence of greater than or equal to an 80% target by 2030). Indicators that provide strong signals in certain epidemic types may not perform consistently well in settings with different epidemiological features. Predicting changes in incidence is more challenging in advanced generalized epidemics compared to concentrated epidemics where changes in high-risk sub-populations track more closely to the population as a whole. Many indicators demonstrate only limited association with incidence (such as "condom use" or "pre-exposure prophylaxis coverage"). This is because many other factors (low effectiveness, impact of other interventions, countervailing changes in risk behaviours, etc.) can confound the relationship between interventions and their ultimate long-term impact, especially for an intervention with low expected coverage. The population prevalence of viral suppression shows the most consistent associations with long-term changes in incidence even in the largest generalized epidemics. CONCLUSIONS Target setting should be appropriate for the local epidemic and what can feasibly be achieved. There is no one universally reliable indicator to predict future HIV incidence across settings. Thus, the signature of epidemic control must contain indications of success across a wide range of interventions and outcomes.
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Affiliation(s)
- Sarah‐Jane Anderson
- Department of Infectious Disease EpidemiologyImperial College LondonLondonUK
| | | | - Joanne Enstone
- Division of Public Health and EpidemiologyThe University of NottinghamNottinghamUK
| | - Timothy B Hallett
- Department of Infectious Disease EpidemiologyImperial College LondonLondonUK
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Krishnaratne S, Hensen B, Cordes J, Enstone J, Hargreaves JR. Interventions to strengthen the HIV prevention cascade: a systematic review of reviews. Lancet HIV 2017; 3:e307-17. [PMID: 27365205 DOI: 10.1016/s2352-3018(16)30038-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 04/22/2016] [Accepted: 05/10/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND Much progress has been made in interventions to prevent HIV infection. However, development of evidence-informed prevention programmes that translate the efficacy of these strategies into population effect remain a challenge. In this systematic review, we map current evidence for HIV prevention against a new classification system, the HIV prevention cascade. METHODS We searched for systematic reviews on the effectiveness of HIV prevention interventions published in English from Jan 1, 1995, to July, 2015. From eligible reviews, we identified primary studies that assessed at least one of: HIV incidence, HIV prevalence, condom use, and uptake of HIV testing. We categorised interventions as those seeking to increase demand for HIV prevention, improve supply of HIV prevention methods, support adherence to prevention behaviours, or directly prevent HIV. For each specific intervention, we assigned a rating based on the number of randomised trials and the strength of evidence. FINDINGS From 88 eligible reviews, we identified 1964 primary studies, of which 292 were eligible for inclusion. Primary studies of direct prevention mechanisms showed strong evidence for the efficacy of pre-exposure prophylaxis (PrEP) and voluntary medical male circumcision. Evidence suggests that interventions to increase supply of prevention methods such as condoms or clean needles can be effective. Evidence arising from demand-side interventions and interventions to promote use of or adherence to prevention tools was less clear, with some strategies likely to be effective and others showing no effect. The quality of the evidence varied across categories. INTERPRETATION There is growing evidence to support a number of efficacious HIV prevention behaviours, products, and procedures. Translating this evidence into population impact will require interventions that strengthen demand for HIV prevention, supply of HIV prevention technologies, and use of and adherence to HIV prevention methods. FUNDING Bill & Melinda Gates Foundation.
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Affiliation(s)
- Shari Krishnaratne
- Department of Social and Environmental Health Research, London School of Hygiene & Tropical Medicine, London, UK; Centre for Evaluation, London School of Hygiene & Tropical Medicine, London, UK.
| | - Bernadette Hensen
- Department of Social and Environmental Health Research, London School of Hygiene & Tropical Medicine, London, UK
| | - Jillian Cordes
- Department of Global Health, Emory University, Atlanta, GA, USA
| | - Joanne Enstone
- Public Health and Epidemiology, School of Medicine, Nottingham University, Nottingham, UK
| | - James R Hargreaves
- Department of Social and Environmental Health Research, London School of Hygiene & Tropical Medicine, London, UK
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Fragaszy E, Ishola DA, Brown IH, Enstone J, Nguyen‐Van‐Tam JS, Simons R, Tucker AW, Wieland B, Williamson SM, Hayward AC, Wood JLN. Increased risk of A(H1N1)pdm09 influenza infection in UK pig industry workers compared to a general population cohort. Influenza Other Respir Viruses 2016; 10:291-300. [PMID: 26611769 PMCID: PMC4910179 DOI: 10.1111/irv.12364] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2015] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND Pigs are mixing vessels for influenza viral reassortment, but the extent of influenza transmission between swine and humans is not well understood. OBJECTIVES To assess whether occupational exposure to pigs is a risk factor for human infection with human and swine-adapted influenza viruses. METHODS UK pig industry workers were frequency-matched on age, region, sampling month, and gender with a community-based comparison group from the Flu Watch study. HI assays quantified antibodies for swine and human A(H1) and A(H3) influenza viruses (titres ≥ 40 considered seropositive and indicative of infection). Virus-specific associations between seropositivity and occupational pig exposure were examined using multivariable regression models adjusted for vaccination. Pigs on the same farms were also tested for seropositivity. RESULTS Forty-two percent of pigs were seropositive to A(H1N1)pdm09. Pig industry workers showed evidence of increased odds of A(H1N1)pdm09 seropositivity compared to the comparison group, albeit with wide confidence intervals (CIs), adjusted odds ratio after accounting for possible cross-reactivity with other swine A(H1) viruses (aOR) 25·3, 95% CI (1·4-536·3), P = 0·028. CONCLUSION The results indicate that A(H1N1)pdm09 virus was common in UK pigs during the pandemic and subsequent period of human A(H1N1)pdm09 circulation, and occupational exposure to pigs was a risk factor for human infection. Influenza immunisation of pig industry workers may reduce transmission and the potential for virus reassortment.
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Affiliation(s)
- Ellen Fragaszy
- Department of Infectious Disease InformaticsFarr Institute of Health Informatics ResearchUniversity College LondonLondonUK
- Department of Infectious Disease EpidemiologyLondon School of Hygiene and Tropical MedicineLondonUK
| | - David A. Ishola
- Department of Infectious Disease InformaticsFarr Institute of Health Informatics ResearchUniversity College LondonLondonUK
- Immunisation DepartmentPublic Health EnglandLondonUK
| | - Ian H. Brown
- Animal and Plant Health Agency (formerly Animal Health and Veterinary Laboratories Agency)WeybridgeUK
| | - Joanne Enstone
- Health Protection and Influenza Research GroupDivision of Epidemiology and Public HealthUniversity of NottinghamNottinghamUK
| | - Jonathan S. Nguyen‐Van‐Tam
- Health Protection and Influenza Research GroupDivision of Epidemiology and Public HealthUniversity of NottinghamNottinghamUK
| | - Robin Simons
- Animal and Plant Health Agency (formerly Animal Health and Veterinary Laboratories Agency)WeybridgeUK
| | - Alexander W. Tucker
- Disease Dynamics UnitDepartment of Veterinary MedicineUniversity of CambridgeCambridgeUK
| | - Barbara Wieland
- Royal Veterinary CollegeNorth MymmsUK
- ILRI: International Livestock Research InstituteAddis AbabaEthiopia
| | - Susanna M. Williamson
- Animal and Plant Health Agency (formerly Animal Health and Veterinary Laboratories Agency)WeybridgeUK
| | - Andrew C. Hayward
- Department of Infectious Disease InformaticsFarr Institute of Health Informatics ResearchUniversity College LondonLondonUK
| | | | - James L. N. Wood
- Disease Dynamics UnitDepartment of Veterinary MedicineUniversity of CambridgeCambridgeUK
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Beck CR, McKenzie BC, Hashim AB, Harris RC, Zanuzdana A, Agboado G, Orton E, Béchard-Evans L, Morgan G, Stevenson C, Weston R, Mukaigawara M, Enstone J, Augustine G, Butt M, Kim S, Puleston R, Dabke G, Howard R, O'Boyle J, O'Brien M, Ahyow L, Denness H, Farmer S, Figureroa J, Fisher P, Greaves F, Haroon M, Haroon S, Hird C, Isba R, Ishola DA, Kerac M, Parish V, Roberts J, Rosser J, Theaker S, Wallace D, Wigglesworth N, Lingard L, Vinogradova Y, Horiuchi H, Peñalver J, Nguyen-Van-Tam JS. Influenza vaccination for immunocompromised patients: summary of a systematic review and meta-analysis. Influenza Other Respir Viruses 2014; 7 Suppl 2:72-75. [PMID: 24034488 DOI: 10.1111/irv.12084] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Vaccination of immunocompromised patients is recommended in many national guidelines to protect against severe or complicated influenza infection. However, due to uncertainties over the evidence base, implementation is frequently patchy and dependent on individual clinical discretion. We conducted a systematic review and meta-analysis to assess the evidence for influenza vaccination in this patient group. Healthcare databases and grey literature were searched and screened for eligibility. Data extraction and assessments of risk of bias were undertaken in duplicate, and results were synthesised narratively and using meta-analysis where possible. Our data show that whilst the serological response following vaccination of immunocompromised patients is less vigorous than in healthy controls, clinical protection is still meaningful, with only mild variation in adverse events between aetiological groups. Although we encountered significant clinical and statistical heterogeneity in many of our meta-analyses, we advocate that immunocompromised patients should be targeted for influenza vaccination.
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Affiliation(s)
- Charles R Beck
- Division of Epidemiology and Public Health, University of Nottingham, Nottingham, United Kingdom
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Beck CR, McKenzie BC, Hashim AB, Harris RC, Zanuzdana A, Agboado G, Orton E, Béchard-Evans L, Morgan G, Stevenson C, Weston R, Mukaigawara M, Enstone J, Augustine G, Butt M, Kim S, Puleston R, Dabke G, Howard R, O'Boyle J, O'Brien M, Ahyow L, Denness H, Farmer S, Figureroa J, Fisher P, Greaves F, Haroon M, Haroon S, Hird C, Isba R, Ishola DA, Kerac M, Parish V, Roberts J, Rosser J, Theaker S, Wallace D, Wigglesworth N, Lingard L, Vinogradova Y, Horiuchi H, Peñalver J, Nguyen-Van-Tam JS. Influenza vaccination for immunocompromised patients: systematic review and meta-analysis from a public health policy perspective. PLoS One 2011; 6:e29249. [PMID: 22216224 PMCID: PMC3245259 DOI: 10.1371/journal.pone.0029249] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 11/23/2011] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Immunocompromised patients are vulnerable to severe or complicated influenza infection. Vaccination is widely recommended for this group. This systematic review and meta-analysis assesses influenza vaccination for immunocompromised patients in terms of preventing influenza-like illness and laboratory confirmed influenza, serological response and adverse events. METHODOLOGY/PRINCIPAL FINDINGS Electronic databases and grey literature were searched and records were screened against eligibility criteria. Data extraction and risk of bias assessments were performed in duplicate. Results were synthesised narratively and meta-analyses were conducted where feasible. Heterogeneity was assessed using I(2) and publication bias was assessed using Begg's funnel plot and Egger's regression test. Many of the 209 eligible studies included an unclear or high risk of bias. Meta-analyses showed a significant effect of preventing influenza-like illness (odds ratio [OR]=0.23; 95% confidence interval [CI]=0.16-0.34; p<0.001) and laboratory confirmed influenza infection (OR=0.15; 95% CI=0.03-0.63; p=0.01) through vaccinating immunocompromised patie nts compared to placebo or unvaccinated controls. We found no difference in the odds of influenza-like illness compared to vaccinated immunocompetent controls. The pooled odds of seroconversion were lower in vaccinated patients compared to immunocompetent controls for seasonal influenza A(H1N1), A(H3N2) and B. A similar trend was identified for seroprotection. Meta-analyses of seroconversion showed higher odds in vaccinated patients compared to placebo or unvaccinated controls, although this reached significance for influenza B only. Publication bias was not detected and narrative synthesis supported our findings. No consistent evidence of safety concerns was identified. CONCLUSIONS/SIGNIFICANCE Infection prevention and control strategies should recommend vaccinating immunocompromised patients. Potential for bias and confounding and the presence of heterogeneity mean the evidence reviewed is generally weak, although the directions of effects are consistent. Areas for further research are identified.
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Affiliation(s)
- Charles R Beck
- Division of Epidemiology and Public Health, University of Nottingham, Nottingham, United Kingdom.
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Killingley B, Enstone J, Booy R, Hayward A, Oxford J, Ferguson N, Nguyen Van-Tam J. Potential role of human challenge studies for investigation of influenza transmission. Lancet Infect Dis 2011; 11:879-86. [PMID: 21798808 DOI: 10.1016/s1473-3099(11)70142-6] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The importance of different routes of influenza transmission (including the role of bioaerosols) and the ability of masks and hand hygiene to prevent transmission remain poorly understood. Interest in transmission of influenza has grown as the effectiveness of prevention measures implemented during the 2009 H1N1 pandemic are questioned and as plans to better prepare for the next pandemic are debated. Recent studies of naturally infected patients have encountered difficulties and have fallen short of providing definitive answers. Human challenge studies with influenza virus date back to the 1918 pandemic. In more recent decades they have been undertaken to investigate the efficacy of antiviral agents and vaccines. Could experimental challenge studies, in which volunteers are deliberately infected with influenza virus, provide an alternative approach to the study of transmission? Here, we review the latest intervention studies and discuss the potential of challenge studies to address the remaining gaps in our knowledge.
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Affiliation(s)
- Ben Killingley
- Division of Epidemiology and Public Health, University of Nottingham, Nottingham, UK.
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Puleston RL, Bugg G, Hoschler K, Konje J, Thornton J, Stephenson I, Myles P, Enstone J, Augustine G, Davis Y, Zambon M, Nicholson KG, Nguyen-Van-Tam JS. Observational study to investigate vertically acquired passive immunity in babies of mothers vaccinated against H1N1v during pregnancy. Health Technol Assess 2011; 14:1-82. [PMID: 21208547 DOI: 10.3310/hta14550-01] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
OBJECTIVE The primary objective was to determine the proportion of babies who acquired passive immunity to A/H1N1v, born to mothers who accepted vaccination as part of the national vaccination programme while pregnant (during the second and/or third trimesters) against the novel A/H1N1v influenza virus (exposed group) compared with unvaccinated (unexposed) mothers. DESIGN An observational study at three sites in the UK. The purpose was to determine if mothers immunised against A/H1N1v during the pandemic vaccination period transferred that immunity to their child in utero. SETTING Three sites in the UK [Queen's Medical Centre, Nottingham; City Hospital, Nottingham (both forming University Hospitals Nottingham), and Leicester Royal Infirmary (part of University Hospitals Leicester)]. PARTICIPANTS All pregnant women in the second and third trimester presenting at the NHS hospitals above to deliver were eligible to participate in the study. Women were included regardless of age, social class, ethnicity, gravida and parity status, past and current medical history (including current medications), ethnicity, mode of delivery and pregnancy outcome (live/stillbirth). INTERVENTIONS At enrolment, participants provided written consent and completed a questionnaire. At parturition, venous cord blood was obtained for serological antibody analysis. Serological analysis was undertaken by the Respiratory Virus Unit (RVU), Health Protection Agency (HPA) Centre for Infections, London. MAIN OUTCOME MEASURES The primary end point in the study was the serological results of the cord blood samples for immunity to A/H1N1v. Regarding a suitable threshold for the determination of a serological response consistent with clinical protection, this issue is somewhat complex for pandemic influenza. The European Medicines Agency (EMEA) Committee for Human Medicinal Products (CHMP) judges that a haemagglutination inhibition (HI) titre of 1 : 40 is an acceptable threshold. However, this level was set in the context of licensing plain trivalent seasonal vaccine, where a titre of 1 : 40 is but one of several related immunogenicity criteria, and supported by paired sera capable of demonstrating a fourfold rise in antibody titre in response to vaccination. The current study mainly investigated the effects of an AS03-adjuvanted monovalent vaccine, and it was not possible to obtain paired sera where the initial sample was taken before vaccination (in vaccinated subjects). Of possibly greater relevance is the fact that it has been established from the study of early outbreaks of pandemic influenza in secondary schools in the UK (HPA, unpublished observations) that an HI antibody titre of 1 : 32 seems to be the threshold for a humoral response to 'wild-type' A/H1N1v infection. On that basis, a threshold of 1 : 32 is at least as appropriate as one of 1 : 40, especially in unvaccinated individuals. Given the difficulties that would accrue by applying thresholds of 1 : 32 in unvaccinated patients and 1 : 40 in vaccinated patients, we have therefore applied a threshold of 1 : 32 and 1 : 40, to increase the robustness of our findings. Differences arising are described. A microneutralisation (MN) titre of 1 : 40 may be also used, although it is not part of the CHMP criteria for vaccine licensure. Nonetheless, we utilised this analysis as a secondary end point, based on a conservative threshold of 1 : 60. RESULTS Reverse cumulative distribution percentage curves for haemagglutinin dilution and MN titres demonstrate background immunity in babies of unvaccinated mothers of 25%-30%. Humoral immunity in babies of vaccinated mothers was present in 80% of the group. The difference in positive immunity between the babies of unvaccinated and vaccinated mothers was statistically significant (chi-squared test, p < 0.001). CONCLUSIONS Our findings reveal a highly significant difference in HI titres between babies born to mothers vaccinated with pandemic-specific vaccine against A/H1N1v during the 2009-10 pandemic period. The subjects recruited were comparable from a baseline perspective and thus do not represent different groups that otherwise could have introduced bias into the study. Continued circulation of 2009 A/H1N1-like viruses is uncertain, but is possible as seasonal influenza in years to come. It is possible that future seasonal waves may display increased virulence. Given the adverse outcomes experienced for a small proportion of pregnant women during the influenza pandemic of 2009-10, this study provides useful evidence to support vaccination in pregnancy to protect both the mother and baby. FUNDING The National Institute for Health Research Health Technology Assessment programme.
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Troko J, Myles P, Gibson J, Hashim A, Enstone J, Kingdon S, Packham C, Amin S, Hayward A, Nguyen Van-Tam J. Is public transport a risk factor for acute respiratory infection? BMC Infect Dis 2011. [PMID: 21235795 DOI: 10.1186/1471-2334-11-16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023] Open
Abstract
BACKGROUND The relationship between public transport use and acquisition of acute respiratory infection (ARI) is not well understood but potentially important during epidemics and pandemics. METHODS A case-control study performed during the 2008/09 influenza season. Cases (n = 72) consulted a General Practitioner with ARI, and controls with another non-respiratory acute condition (n = 66). Data were obtained on bus or tram usage in the five days preceding illness onset (cases) or the five days before consultation (controls) alongside demographic details. Multiple logistic regression modelling was used to investigate the association between bus or tram use and ARI, adjusting for potential confounders. RESULTS Recent bus or tram use within five days of symptom onset was associated with an almost six-fold increased risk of consulting for ARI (adjusted OR = 5.94 95% CI 1.33-26.5). The risk of ARI appeared to be modified according to the degree of habitual bus and tram use, but this was not statistically significant (1-3 times/week: adjusted OR = 0.54 (95% CI 0.15-1.95; >3 times/week: 0.37 (95% CI 0.13-1.06). CONCLUSIONS We found a statistically significant association between ARI and bus or tram use in the five days before symptom onset. The risk appeared greatest among occasional bus or tram users, but this trend was not statistically significant. However, these data are plausible in relation to the greater likelihood of developing protective antibodies to common respiratory viruses if repeatedly exposed. The findings have differing implications for the control of seasonal acute respiratory infections and for pandemic influenza.
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Affiliation(s)
- Joy Troko
- University of Nottingham, City Hospital, UK
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Troko J, Myles P, Gibson J, Hashim A, Enstone J, Kingdon S, Packham C, Amin S, Hayward A, Nguyen Van-Tam J. Is public transport a risk factor for acute respiratory infection? BMC Infect Dis 2011; 11:16. [PMID: 21235795 PMCID: PMC3030548 DOI: 10.1186/1471-2334-11-16] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 01/14/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The relationship between public transport use and acquisition of acute respiratory infection (ARI) is not well understood but potentially important during epidemics and pandemics. METHODS A case-control study performed during the 2008/09 influenza season. Cases (n = 72) consulted a General Practitioner with ARI, and controls with another non-respiratory acute condition (n = 66). Data were obtained on bus or tram usage in the five days preceding illness onset (cases) or the five days before consultation (controls) alongside demographic details. Multiple logistic regression modelling was used to investigate the association between bus or tram use and ARI, adjusting for potential confounders. RESULTS Recent bus or tram use within five days of symptom onset was associated with an almost six-fold increased risk of consulting for ARI (adjusted OR = 5.94 95% CI 1.33-26.5). The risk of ARI appeared to be modified according to the degree of habitual bus and tram use, but this was not statistically significant (1-3 times/week: adjusted OR = 0.54 (95% CI 0.15-1.95; >3 times/week: 0.37 (95% CI 0.13-1.06). CONCLUSIONS We found a statistically significant association between ARI and bus or tram use in the five days before symptom onset. The risk appeared greatest among occasional bus or tram users, but this trend was not statistically significant. However, these data are plausible in relation to the greater likelihood of developing protective antibodies to common respiratory viruses if repeatedly exposed. The findings have differing implications for the control of seasonal acute respiratory infections and for pandemic influenza.
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Affiliation(s)
- Joy Troko
- University of Nottingham, City Hospital, UK
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Humphreys H, Newcombe R, Enstone J, Smyth E, McIlvenny G, Davies E, Spencer R. Four country healthcare-associated infection prevalence survey: pneumonia and lower respiratory tract infections. J Hosp Infect 2010; 74:266-70. [DOI: 10.1016/j.jhin.2009.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2009] [Accepted: 10/02/2009] [Indexed: 10/19/2022]
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Smyth E, McIlvenny G, Enstone J, Spencer R, Humphreys H, Davies E, Newcombe R. Response to Dr Wilson, Dr Charlett, and Dr Pearson. Pitfalls in the comparison of intercountry prevalence of healthcare-associated infection (HCAI). J Hosp Infect 2009. [DOI: 10.1016/j.jhin.2008.11.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Humphreys H, Newcombe R, Enstone J, Smyth E, McIlvenny G, Fitzpatrick F, Fry C, Spencer R. Four Country Healthcare Associated Infection Prevalence Survey 2006: risk factor analysis. J Hosp Infect 2008; 69:249-57. [DOI: 10.1016/j.jhin.2008.04.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Accepted: 04/18/2008] [Indexed: 10/22/2022]
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