Imperial College London

ProfessorNicholasGrassly

Faculty of MedicineSchool of Public Health

Prof of Infectious Disease & Vaccine Epidemiology
 
 
 
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Contact

 

+44 (0)20 7594 3264n.grassly Website

 
 
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Location

 

G36Medical SchoolSt Mary's Campus

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Summary

 

Publications

Publication Type
Year
to

124 results found

Mangal TD, Aylward RB, Grassly NC, 2013, The Potential Impact of Routine Immunization with Inactivated Poliovirus Vaccine on Wild-type or Vaccine-derived Poliovirus Outbreaks in a Posteradication Setting, AMERICAN JOURNAL OF EPIDEMIOLOGY, Vol: 178, Pages: 1579-1587, ISSN: 0002-9262

Journal article

Grassly NC, 2013, The final stages of the global eradication of poliomyelitis, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 368, ISSN: 0962-8436

Journal article

Doddington BJ, Bosch J, Oliver JA, Grassly NC, Garcia G, Schmidt BR, Garner TWJ, Fisher MCet al., 2013, Context-dependent amphibian host population response to an invading pathogen, ECOLOGY, Vol: 94, Pages: 1795-1804, ISSN: 0012-9658

Journal article

Koukounari A, Moustaki I, Grassly NC, Blake IM, Basanez M-G, Gambhir M, Mabey DCW, Bailey RL, Burton MJ, Solomon AW, Donnelly CAet al., 2013, Using a Nonparametric Multilevel Latent Markov Model to Evaluate Diagnostics for Trachoma, American Journal of Epidemiology, Vol: 177, Pages: 913-922, ISSN: 0002-9262

In disease control or elimination programs, diagnostics are essential for assessing the impact of interventions, refining treatment strategies, and minimizing the waste of scarce resources. Although high-performance tests are desirable, increased accuracy is frequently accompanied by a requirement for more elaborate infrastructure, which is often not feasible in the developing world. These challenges are pertinent to mapping, impact monitoring, and surveillance in trachoma elimination programs. To help inform rational design of diagnostics for trachoma elimination, we outline a nonparametric multilevel latent Markov modeling approach and apply it to 2 longitudinal cohort studies of trachoma-endemic communities in Tanzania (2000–2002) and The Gambia (2001–2002) to provide simultaneous inferences about the true population prevalence of Chlamydia trachomatis infection and disease and the sensitivity, specificity, and predictive values of 3 diagnostic tests for C. trachomatis infection. Estimates were obtained by using data collected before and after mass azithromycin administration. Such estimates are particularly important for trachoma because of the absence of a true “gold standard” diagnostic test for C. trachomatis. Estimated transition probabilities provide useful insights into key epidemiologic questions about the persistence of disease and the clearance of infection as well as the required frequency of surveillance in the postelimination setting.

Journal article

O'Reilly KM, Durry E, ul Islam O, Quddus A, Abid N, Mir TP, Tangermann RH, Aylward RB, Grassly NCet al., 2012, The effect of mass immunisation campaigns and new oral poliovirus vaccines on the incidence of poliomyelitis in Pakistan and Afghanistan, 2001-11: a retrospective analysis, LANCET, Vol: 380, Pages: 491-498, ISSN: 0140-6736

Journal article

Grassly NC, Jafari H, Bahl S, Sethi R, Deshpande JM, Wolff C, Sutter RW, Aylward RBet al., 2012, Waning Intestinal Immunity After Vaccination With Oral Poliovirus Vaccines in India, JOURNAL OF INFECTIOUS DISEASES, Vol: 205, Pages: 1554-1561, ISSN: 0022-1899

Journal article

Solomon AW, Engels D, Bailey RL, Blake IM, Brooker S, Chen JX, Chen JH, Churcher TS, Drakely CJ, Edwards T, Fenwick A, French MD, Gabrielli AF, Grassly NC, Harding-Esch E, Holland MJ, Koukounari A, Lammie PJ, Leslie J, Mabey DCW, Rhajaoui M, Secor WE, Stothard JR, Wei H, Willingham AL, Zhou XN, Peeling RWet al., 2012, A Diagnostics Platform for the Integrated Mapping, Monitoring and Surveillance of Neglected Tropical Diseases: Rationale and Target Product Profiles, PLoS Neglected Tropical Diseases

Journal article

Marsh KA, Nyamukapa CA, Donnelly CA, Garcia-Calleja JM, Mushati P, Garnett GP, Mpandaguta E, Grassly NC, Gregson Set al., 2011, Monitoring trends in HIV prevalence among young people, aged 15 to 24 years, in Manicaland, Zimbabwe, Journal of the International AIDS Society, Vol: 14, ISSN: 1758-2652

Journal article

O'Reilly KM, Chauvin C, Aylward RB, Maher C, Okiror S, Wolff C, Nshmirimana D, Donnelly CA, Grassly NCet al., 2011, A statistical model of the international spread of wild poliovirus in Africa used to predict and prevent outbreaks, PLoS Med, Vol: 8, Pages: 1-10, ISSN: 1549-1676

BACKGROUND: Outbreaks of poliomyelitis in African countries that were previously free of wild-type poliovirus cost the Global Polio Eradication Initiative US$850 million during 2003-2009, and have limited the ability of the program to focus on endemic countries. A quantitative understanding of the factors that predict the distribution and timing of outbreaks will enable their prevention and facilitate the completion of global eradication. METHODS AND FINDINGS: Children with poliomyelitis in Africa from 1 January 2003 to 31 December 2010 were identified through routine surveillance of cases of acute flaccid paralysis, and separate outbreaks associated with importation of wild-type poliovirus were defined using the genetic relatedness of these viruses in the VP1/2A region. Potential explanatory variables were examined for their association with the number, size, and duration of poliomyelitis outbreaks in 6-mo periods using multivariable regression analysis. The predictive ability of 6-mo-ahead forecasts of poliomyelitis outbreaks in each country based on the regression model was assessed. A total of 142 genetically distinct outbreaks of poliomyelitis were recorded in 25 African countries, resulting in 1-228 cases (median of two cases). The estimated number of people arriving from infected countries and <5-y childhood mortality were independently associated with the number of outbreaks. Immunisation coverage based on the reported vaccination history of children with non-polio acute flaccid paralysis was associated with the duration and size of each outbreak, as well as the number of outbreaks. Six-month-ahead forecasts of the number of outbreaks in a country or region changed over time and had a predictive ability of 82%. CONCLUSIONS: Outbreaks of poliomyelitis resulted primarily from continued transmission in Nigeria and the poor immunisation status of populations in neighbouring countries. From 1 January 2010 to 30 June 2011, reduced transmission in Nigeria and in

Journal article

Gambhir M, Basanez MG, Blake IM, Grassly Net al., 2010, Modelling trachoma for control programmes, Modelling Parasite Transmission and Control, Editors: Michael, Spear, Publisher: Austin, Texas: Landes Bioscience, ISBN: 9781441960641

Book chapter

Blake IM, Burton MJ, Solomon AW, West SK, Basanez M-G, Gambhir M, Bailey RL, Mabey DCW, Grassly NCet al., 2010, Targeting Antibiotics to Households for Trachoma Control, PLOS NEGLECTED TROPICAL DISEASES, Vol: 4, ISSN: 1935-2735

Journal article

Jenkins HE, Aylward RB, Gasasira A, Donnelly CA, Mwanza M, Corander J, Garnier S, Chauvin C, Abanida E, Pate MA, Adu F, Baba M, Grassly NCet al., 2010, Implications of a Circulating Vaccine-Derived Poliovirus in Nigeria., NEW ENGLAND JOURNAL OF MEDICINE, Vol: 362, Pages: 2360-2369, ISSN: 0028-4793

Journal article

Grassly NC, Jafari H, Bahl S, Durrani S, Wenger J, Sutter RW, Aylward RBet al., 2010, Asymptomatic Wild-Type Poliovirus Infection in India among Children with Previous Oral Poliovirus Vaccination, JOURNAL OF INFECTIOUS DISEASES, Vol: 201, Pages: 1535-1543, ISSN: 0022-1899

Journal article

Gambhir M, Basanez M-G, Blake IM, Grassly NCet al., 2010, Modelling Trachoma for Control Programmes, MODELLING PARASITE TRANSMISSION AND CONTROL, Vol: 673, Pages: 141-156, ISSN: 0065-2598

Journal article

Ribas L, Li MS, Doddington BJ, Robert J, Seidel JA, Kroll JS, Zimmerman LB, Grassly NC, Garner TW, Fisher MCet al., 2009, Expression Profiling the Temperature-Dependent Amphibian Response to Infection by Batrachochytrium dendrobatidis, PLOS One, Vol: 4, ISSN: 1932-6203

Amphibians are experiencing a panzootic of unprecedented proportions caused by the emergence of Batrachochytrium dendrobatidis (Bd). However, all species are not equally at risk of infection, and risk is further modified by environmental variables, specifically temperature. In order to understand how, and when, hosts mount a response to Bd we analysed infection dynamics and patterns of gene expression in the model amphibian species Silurana (Xenopus) tropicalis. Mathematical modelling of infection dynamics demonstrate the existence of a temperature-dependent protective response that is largely independent of the intrinsic growth-rate of Bd. Using temporal expression-profiling by microarrays and qRT-PCR, we characterise this response in the main amphibian lymphoid tissue, the spleen. We demonstrate that clearance of Bd at the host-optimal temperature is not clearly associated with an adaptive immune response, but rather is correlated with the induction of components of host innate immunity including the expression of genes that are associated with the production of the antimicrobial skin peptide preprocareulein (PPCP) as well as inflammatory responses. We find that adaptive immunity appears to be lacking at host-optimal temperatures. This suggests that either Bd does not stimulate, or suppresses, adaptive immunity, or that trade-offs exist between innate and adaptive limbs of the amphibian immune system. At cold temperatures, S. tropicalis loses the ability to mount a PPCP-based innate response, and instead manifests a more pronounced inflammatory reaction that is characterised by the production of proteases and higher pathogen burdens. This study demonstrates the temperature-dependency of the amphibian response to infection by Bd and indicates the influence that changing climates may exert on the ectothermic host response to pathogens.

Journal article

Grassly NC, Jafari H, Bahl S, Durrani S, Wenger J, Sutter RW, Aylward RBet al., 2009, Mucosal Immunity after Vaccination with Monovalent and Trivalent Oral Poliovirus Vaccine in India, JOURNAL OF INFECTIOUS DISEASES, Vol: 200, Pages: 794-801, ISSN: 0022-1899

Journal article

Fraser C, Donnelly CA, Cauchemez S, Hanage WP, Van Kerkhove MD, Hollingsworth TD, Griffin J, Baggaley RF, Jenkins HE, Lyons EJ, Jombart T, Hinsley WR, Grassly NC, Balloux F, Ghani AC, Rambaut A, Ferguson NMet al., 2009, Influenza: Making Privileged Data Public Response, SCIENCE, Vol: 325, Pages: 1072-1073, ISSN: 0036-8075

Journal article

Fraser C, Donnelly CA, Cauchemez S, Hanage WP, Van Kerkhove MD, Hollingsworth TD, Griffin J, Baggaley RF, Jenkins HE, Lyons EJ, Jombart T, Hinsley WR, Grassly NC, Balloux F, Ghani AC, Ferguson NM, Rambaut A, Pybus OG, Lopez-Gatell H, Alpuche-Aranda CM, Bojorquez Chapela I, Palacios Zavala E, Espejo Guevara DM, Checchi F, Garcia E, Hugonnet S, Roth Cet al., 2009, Pandemic Potential of a Strain of Influenza A (H1N1): Early Findings, SCIENCE, Vol: 324, Pages: 1557-1561, ISSN: 0036-8075

Journal article

Gambhir M, Basanez M-G, Burton MJ, Solomon AW, Bailey RL, Holland MJ, Blake IM, Donnelly CA, Jabr I, Mabey DC, Grassly NCet al., 2009, The Development of an Age-Structured Model for Trachoma Transmission Dynamics, Pathogenesis and Control, PLOS Neglected Tropical Diseases, Vol: 3, ISSN: 1935-2735

Background: Trachoma, the worldwide leading infectious cause of blindness, is due to repeated conjunctival infection with Chlamydia trachomatis. The effects of control interventions on population levels of infection and active disease can be promptly measured, but the effects on severe ocular sequelae require long-term monitoring. We present an age-structured mathematical model of trachoma transmission and disease to predict the impact of interventions on the prevalence of blinding trachoma.Methodology/Principal Findings: The model is based on the concept of multiple reinfections leading to progressive conjunctival scarring, trichiasis, corneal opacity and blindness. It also includes aspects of trachoma natural history, such as an increasing rate of recovery from infection and a decreasing chlamydial load with subsequent infections that depend upon a (presumed) acquired immunity that clears infection with age more rapidly. Parameters were estimated using maximum likelihood by fitting the model to pre-control infection prevalence data from hypo-, meso- and hyperendemic communities from The Gambia and Tanzania. The model reproduces key features of trachoma epidemiology: 1) the age-profile of infection prevalence, which increases to a peak at very young ages and declines at older ages; 2) a shift in this prevalence peak, toward younger ages in higher force of infection environments; 3) a raised overall profile of infection prevalence with higher force of infection; and 4) a rising profile, with age, of the prevalence of the ensuing severe sequelae (trachomatous scarring, trichiasis), as well as estimates of the number of infections that need to occur before these sequelae appear.Conclusions/Significance: We present a framework that is sufficiently comprehensive to examine the outcomes of the A (antibiotic) component of the SAFE strategy on disease. The suitability of the model for representing population-level patterns of infection and disease sequelae is discussed in

Journal article

Blake IM, Burton MJ, Bailey RL, Solomon AW, West S, Munoz B, Holland MJ, Mabey DCW, Gambhir M, Basanez M-G, Grassly NCet al., 2009, Estimating Household and Community Transmission of Ocular Chlamydia trachomatis, PLOS NEGLECTED TROPICAL DISEASES, Vol: 3, ISSN: 1935-2735

Journal article

Grassly NC, Ward ME, Ferris S, Mabey DC, Bailey RLet al., 2008, The Natural History of Trachoma Infection and Disease in a Gambian Cohort with Frequent Follow-Up, PLOS NEGLECTED TROPICAL DISEASES, Vol: 2, ISSN: 1935-2735

Journal article

Jenkins HE, Aylward RB, Gasasira A, Donnelly CA, Abanida EA, Koleosho-Adelekan T, Grassly NCet al., 2008, Effectiveness of immunization against paralytic poliomyelitis in Nigeria, NEW ENGLAND JOURNAL OF MEDICINE, Vol: 359, Pages: 1666-U111, ISSN: 0028-4793

Journal article

Grassly NC, Fraser C, 2008, Mathematical models of infectious disease transmission, NATURE REVIEWS MICROBIOLOGY, Vol: 6, Pages: 477-487, ISSN: 1740-1526

Journal article

Cooper A, Grassly N, Rambaut A, 2007, Using Molecular Data to Estimate Divergence Times, Palaeobiology II, Pages: 532-534, ISBN: 9780632051496

Book chapter

Grassly NC, Wenger J, Aylward RB, 2007, Potent questions about India's polio vaccine - Response, SCIENCE, Vol: 318, Pages: 914-+, ISSN: 0036-8075

Journal article

Grassly NC, Wenger J, Aylward RB, 2007, Response [6], Science, Vol: 318, Pages: 914-916, ISSN: 0036-8075

Journal article

Grassly NC, Wenger J, Bahl S, Sutter RW, Aylward RBet al., 2007, Protective efficacy of a monovalent oral type 1 poliovirus vaccine - Reply, LANCET, Vol: 370, Pages: 129-130, ISSN: 0140-6736

Journal article

Gambhir M, Basanez M-G, Turner F, Kumaresan J, Grassly NCet al., 2007, Trachoma: transmission, infection, and control, LANCET INFECTIOUS DISEASES, Vol: 7, Pages: 420-427, ISSN: 1473-3099

Journal article

Grassly NC, Wenger J, Durrani S, 2007, Protective efficacy of a monovalent oral type 1 poliovirus vaccine: a case-control study (vol 369, pg 1356, 2007), LANCET, Vol: 369, Pages: 1790-1790, ISSN: 0140-6736

Journal article

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