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Biomedical subjects

W John Edmunds

Publications and source records attributed to W John Edmunds.

At least 19 recordsLinked to original sources
PubMed2006

Estimating the cost-effectiveness of detecting cases of chronic hepatitis C infection on reception into prison.

BACKGROUND: In England and Wales where less than 1% of the population are Injecting drug users (IDUs), 97% of HCV reports are attributed to injecting drug use. As over 60% of the IDU population will have been imprisoned by the age of 30 years, prison may provide a good location in which to offer HCV screening and treatment. The aim of this work is to examine the cost effectiveness of a number of alternative HCV case-finding strategies on prison reception METHODS: A decision analysis model embedded in a model of the flow of IDUs through prison was used to estimate the cost effectiveness of a number of alternative case-finding strategies. The model estimates the average cost of identifying a new case of HCV from the perspective of the health care provider and how these estimates may evolve over time. RESULTS: The results suggest that administering verbal screening for a past positive HCV test and for ever having engaged in illicit drug use prior to the administering of ELISA and PCR tests can have a significant impact on the cost effectiveness of HCV case-finding strategies on prison reception; the discounted cost in 2017 being pound2,102 per new HCV case detected compared to pound3,107 when no verbal screening is employed. CONCLUSION: The work here demonstrates the importance of targeting those individuals that have ever engaged in illicit drug use for HCV testing in prisons, these individuals can then be targeted for future intervention measures such as treatment or monitored to prevent future transmission.

Adult↗
PubMed2006

Delaying the international spread of pandemic influenza.

BACKGROUND: The recent emergence of hypervirulent subtypes of avian influenza has underlined the potentially devastating effects of pandemic influenza. Were such a virus to acquire the ability to spread efficiently between humans, control would almost certainly be hampered by limited vaccine supplies unless global spread could be substantially delayed. Moreover, the large increases that have occurred in international air travel might be expected to lead to more rapid global dissemination than in previous pandemics. METHODS AND FINDINGS: To evaluate the potential of local control measures and travel restrictions to impede global dissemination, we developed stochastic models of the international spread of influenza based on extensions of coupled epidemic transmission models. These models have been shown to be capable of accurately forecasting local and global spread of epidemic and pandemic influenza. We show that under most scenarios restrictions on air travel are likely to be of surprisingly little value in delaying epidemics, unless almost all travel ceases very soon after epidemics are detected. CONCLUSIONS: Interventions to reduce local transmission of influenza are likely to be more effective at reducing the rate of global spread and less vulnerable to implementation delays than air travel restrictions. Nevertheless, under the most plausible scenarios, achievable delays are small compared with the time needed to accumulate substantial vaccine stocks.

Disease Outbreaks↗
PubMed2006

Modeling future changes to the meningococcal serogroup C conjugate (MCC) vaccine program in England and Wales.

The UK meningococcal serogroup C conjugate (MCC) vaccine program has successfully controlled serogroup C disease, due to high vaccine effectiveness and substantial herd immunity. However, children immunised at 2, 3 and 4 months of age receive only short-term direct protection and may be at risk of disease 15 months after vaccination. To investigate this we applied a mathematical model to predict the future epidemiology of serogroup C disease, with and without changes to the immunization schedule. Only a few cases of serogroup C disease were predicted to occur over the next few years because of persisting herd immunity, even without a change to the vaccine schedule. The inclusion of a booster dose is likely to improve the impact of the MCC program and reducing the number of doses in infancy will improve cost-effectiveness and create space in the schedule for the addition of other vaccines.

Adolescent↗
PubMed2006

Developing a realistic sexual network model of chlamydia transmission in Britain.

BACKGROUND: A national chlamydia screening programme is currently being rolled out in the UK and other countries. However, much of the epidemiology remains poorly understood. In this paper we present a stochastic, individual based, dynamic sexual network model of chlamydia transmission and its parameterisation. Mathematical models provide a theoretical framework for understanding the key epidemiological features of chlamydia: sexual behaviour, health care seeking and transmission dynamics. RESULTS: The model parameters were estimated either directly or by systematic fitting to a variety of appropriate data sources. The fitted model was representative of sexual behaviour, chlamydia epidemiology and health care use in England. We were able to recapture the observed age distribution of chlamydia prevalence. CONCLUSION: Estimating parameters for models of sexual behaviour and transmission of chlamydia is complex. Most of the parameter values are highly correlated, highly variable and there is little empirical evidence to inform estimates. We used a novel approach to estimate the rate of active treatment seeking, by combining data sources, which improved the credibility of the model results. The model structure is flexible and is broadly applicable to other developed world settings and provides a practical tool for public health decision makers.

Adolescent↗
PubMed2005

The burden of Herpes Zoster: a prospective population based study.

We analysed prospectively the medical, societal and economic burden among patients from 18 general practices in East London, serving 158,716 patients who presented to their general practitioners with acute Herpes Zoster over an 8-month period. One hundred and eighty-six patients with HZ were seen by GPs during the study period, of whom 96 were referred, 70 enrolled and 65 completed. PHN occurred in 13.4% of patients. The average overall cost of HZ in the first 6 months was calculated at pound524 per patient. Medical costs were highest in those aged over 65 and societal costs highest in those aged under 65 years.

Age Factors↗
PubMed2005

Dynamic models of meningococcal carriage, disease, and the impact of serogroup C conjugate vaccination.

Much interest has surrounded the use of conjugate vaccines in recent years, with the development of vaccines against disease caused by Haemophilus influenzae type b, Neisseria meningitidis, and Streptococcus pneumoniae. These vaccines offer the potential for safe and effective disease control, but some questions remain, particularly regarding the duration and mechanisms of protection and the longer-term impact of vaccination on carriage. In this paper, the authors use data on immunization with serogroup C meningococcal conjugate vaccines in England and Wales to develop and apply a mathematical model to investigate the direct and indirect (herd immunity) effects of a conjugate vaccine program. A realistic, age-structured, dynamic model was developed and parameterized and was fitted to epidemiologic data from England and Wales. The effects of a range of vaccine strategies, including hypothetical scenarios, were investigated. The basic reproduction number was estimated to be 1.36. Catch-up vaccination targeting teenagers generated substantial herd immunity and was important in controlling disease rapidly. The results were sensitive to changes in the assumptions regarding the method of vaccine action, particularly duration of protection and efficacy of vaccination against carriage acquisition. This model can be used to help predict the potential impact of vaccine strategies both in the United Kingdom and elsewhere.

Adolescent↗
PubMed2005

The role of economic evaluation in vaccine decision making: focus on meningococcal group C conjugate vaccine.

In recent years, several countries have experienced increases in the incidence of serogroup C meningococcal disease. It can be controlled with older polysaccharide vaccines and particularly the recently developed conjugate vaccines. For 21 developed countries, we investigated the role that economic evaluation played in the decision to introduce the conjugate vaccine into either the routine childhood vaccination schedule, as a mass vaccination 'catch-up' campaign or not at all. A literature review was performed and experts from these countries were contacted. For six countries, we identified published economic evaluations for meningococcal C conjugate vaccination. In four of them (Australia, Canada [Quebec], The Netherlands and the UK) the analyses were performed before a decision about the use of the conjugate vaccine was made. In all of these countries, the economic evaluation offered guidance as to the most efficient way to add the conjugate vaccine to the routine infant immunisation schedule and, in three countries, this advice was adopted by decision makers. In Portugal and Switzerland, initial vaccination decisions were made without the economic evaluations that are influencing current decision making. Of the countries without economic evaluations, six implemented vaccination programmes. Overall, there was a positive correlation between the reported incidence of meningococcal C disease and (a) the decision to vaccinate and (b) performing an economic evaluation. All economic evaluations were modelling studies. The reported cost-effectiveness ratios were sensitive to the age of vaccination, the future meningococcal incidence, vaccine price and some methodological characteristics that varied widely between studies making direct comparisons difficult. In conclusion, in almost all countries where economic evaluations for meningococcal C conjugate vaccinations have been conducted, their results had an important role in the decision-making process. However, in most countries with strongly increasing meningococcal incidence, public health considerations took precedence. In order to improve the international comparability of such studies, firmer national and international modelling guidelines and better adherence to such guidelines seem necessary.

Cost-Benefit Analysis↗
PubMed2004

Incidence and routes of transmission of hepatitis B virus in England and Wales, 1995-2000: implications for immunisation policy.

BACKGROUND: The incidence of hepatitis B virus (HBV) infection in the UK is low. Since the infection can have serious sequelae, there is a continuing need to examine its epidemiology so as to inform control measures. OBJECTIVES: We aimed to describe the current HBV incidence and patterns of transmission in the UK, to estimate the rate of new carrier infections, and to discuss implications for the control of HBV through immunisation. STUDY DESIGN: We analysed routine England and Wales laboratory surveillance data of acute HBV infection (1995-2000) and data on migration and global HBsAg prevalence. RESULTS: The estimated annual incidence of HBV infection in England and Wales was 7.4 per 100,000. Injecting drug use was the most frequently reported route of transmission. The number of cases attributed to heterosexual contact was fairly stable, whereas the number of cases in men having sex with men decreased. These observations continue trends reported for the early 1990s. Transmission during childhood was rarely reported, but was more frequent among South Asians. The incidence in South Asians is relatively high, and their main risk factors are medical treatment overseas and heterosexual contact. For about a third of cases of acute HBV infection no route of transmission is reported, but analysis of secular trends and age distribution suggest that many of these may be related to injecting drug use. Endemic transmission gives rise to only a small proportion of all new chronic infections, with the vast majority arising from immigration of established HBV carriers. CONCLUSIONS: The incidence of acute HBV infection in England and Wales has remained low, with a similar pattern of reported routes of transmission compared to the early 1990s. The UK prevalence of HBV infection is dependant on global rather than national immunisation policy. Endemic transmission may be reduced by improving immunisation coverage among injecting drug users, which is expected to also reduce the number of cases without a risk factor reported. In addition, immunisation options that better suit the needs of ethnic minorities need to be explored.

Disease Transmission, Infectious↗
PubMed2004

The 23-valent pneumococcal polysaccharide vaccine. Part I. Efficacy of PPV in the elderly: a comparison of meta-analyses.

A 23-valent polysaccharide pneumococcal vaccine (PPV) has been available in the UK for more than 20 years and is currently recommended for use in high-risk groups (HRG) of 2+ years of age. The degree of protection afforded by the PPV remains a critical issue, although a number of randomised clinical trials and case-control studies (CCS) have been published. The aim of this work is to review the estimates on the efficacy of PPV against pneumococcal pneumonia and invasive pneumococcal disease (IPD) in the elderly and to perform a meta-analysis in order to obtain a pooled estimate of the level of protection in high and low risk individuals. These two groups of individuals are at the centre of the current debate on whether or not to extend the vaccination programme to all elderly individuals 65+. Only randomised and quasi-randomised studies are included in the analysis and results are compared with previous meta-analyses. The effect of the inclusion of observational studies is investigated in the sensitivity analysis. When taken with the results of other meta-analyses and observational studies, it appears that PPV offers protection against IPD in the general elderly population (VE = 65%; 95% CI: -49-92%) whereas it has a moderate effect in the high-risk elderly (VE = 20%; 95% CI: -188-78%). The vaccine has little or no effect against pneumonia (VE = 16% in the general elderly and -20% in HRG).

Aged↗
PubMed2004

The 23-valent pneumococcal polysaccharide vaccine. Part II. A cost-effectiveness analysis for invasive disease in the elderly in England and Wales.

The 23-valent pneumococcal polysaccharide vaccine (PPV) has been available for a number of years and is recommended for high-risk categories. Relatively immunocompetent elderly people are not included in this group, although their probability of getting invasive pneumococcal infection is high. The objective of this study was to assess whether vaccinating all elderly people over 65 years of age was a cost-effective policy for England and Wales. The analysis was performed comparing the cost and health effects produced by vaccination, to what would have been occurred if vaccination were not introduced. A decision analysis model was used in order to predict health outcomes under different vaccination scenarios. Unit costs were applied to the outcome and the cost per life-year gained was calculated. Sensitivity analysis was performed to allow for uncertain parameters to vary. The current UK recommendation does not appear to be the most cost-effective strategy due to the low level of efficacy of the vaccine in high-risk groups (HRG) and their shorter life expectancy. Routine vaccination of all elderly appears to be more cost-effective. These results are, nevertheless, very much dependent on the uncertainties around vaccine efficacy estimates, which appear to be still present, especially in HRG, and on the number of hospitalisations and deaths attributable to invasive pneumococcal disease (IPD).

Aged↗
PubMed2004

Epidemiology and cost of nosocomial gastroenteritis, Avon, England, 2002-2003.

Healthcare-associated outbreaks of gastroenteritis are an increasingly recognized problem, but detailed knowledge of the epidemiology of these events is lacking. We actively monitored three hospital systems in England for outbreaks of gastroenteritis in 2002 to 2003. A total of 2,154 patients (2.21 cases/1,000-hospital-days) and 1,360 healthcare staff (0.47 cases/1,000-hospital-days) were affected in 227 unit outbreaks (1.33 outbreaks/unit-year). Norovirus, detected in 63% of outbreaks, was the predominant etiologic agent. Restricting new admissions to affected units resulted in 5,443 lost bed-days. The cost of bed-days lost plus staff absence was calculated to be 635,000 pounds sterling (US. 1.01 million dollars) per 1,000 beds. By our extrapolation, gastroenteritis outbreaks likely cost the English National Health Service 115 million pounds sterling (US 184 million dollars) in 2002 to 2003. Outbreaks were contained faster (7.9 vs. 15.4 days, p = 0.0023) when units were rapidly closed to new admissions (<4 days). Implementing control measures rapidly may be effective in controlling outbreaks.

Adolescent↗
PubMed2003

Planning for smallpox outbreaks.

Mathematical models of viral transmission and control are important tools for assessing the threat posed by deliberate release of the smallpox virus and the best means of containing an outbreak. Models must balance biological realism against limitations of knowledge, and uncertainties need to be accurately communicated to policy-makers. Smallpox poses the particular challenge that key biological, social and spatial factors affecting disease spread in contemporary populations must be elucidated largely from historical studies undertaken before disease eradication in 1979. We review the use of models in smallpox planning within the broader epidemiological context set by recent outbreaks of both novel and re-emerging pathogens.

Bioterrorism↗
PubMed2003

Future savings from measles eradication in industrialized countries.

Estimates are made of monetary savings associated with measles eradication in seven industrialized countries. Three scenarios were studied: First, changing from the present two-dose measles-mumps-rubella (MMR) immunization schedule to one-dose of MMR; second, the use of an MMR and mumps-rubella schedule; or third, continuing the present schedule. Results show that the largest savings (US $623 million) would be achieved by changing to a one-dose MMR schedule with an assumption of a 3% discount rate and measles eradication in 2010. The smallest overall savings would result from option 3, by use of a 5% discount rate and the assumption that measles eradication occurs in 2020 ($10 million). These savings are less than previously estimated for the United States, partly because of the assumption that measles vaccines will continue to be delivered in response to possible bioterrorism threats.

Canada↗
PubMed2003

The cost-effectiveness of syndromic management in pharmacies in Lima, Peru.

BACKGROUND: Many people with sexually transmitted diseases (STDs) in Lima, Peru, seek treatment in pharmacies. GOAL: The goal was to assess the cost-effectiveness of training pharmacy workers in syndromic management of STDs. STUDY DESIGN: Cost-effectiveness from both the program and societal perspectives was determined on the basis of study costs, societal costs (cost of medicine), and the number of cases adequately managed. The latter was calculated from estimated incidence, proportion of symptomatic patients, proportion seeking treatment in pharmacies, and proportion of cases adequately managed in both comparison and intervention districts. Univariate and multivariate sensitivity analyses were performed. RESULTS: Under base-case assumptions, from the societal perspective the intervention saved an estimated US$1.51 per case adequately managed; from the program perspective, it cost an estimated US$3.67 per case adequately managed. In the sensitivity analyses, the proportion of females with vaginal discharge or pelvic inflammatory disease who seek treatment in pharmacies had the greatest impact on the estimated cost-effectiveness, along with the medication costs under the societal perspective. CONCLUSION: Training pharmacists in syndromic management of STDs appears to be cost-effective when only program costs are used and cost-saving from the societal perspective. Our methods provide a template for assessing the cost-effectiveness of managing STD syndromes, on the basis of indirect estimates of effectiveness.

Anti-Infective Agents↗
PubMed2002

The average cost of measles cases and adverse events following vaccination in industrialised countries.

BACKGROUND: Even though the annual incidence rate of measles has dramatically decreased in industrialised countries since the implementation of universal immunisation programmes, cases continue to occur in countries where endemic measles transmission has been interrupted and in countries where adequate levels of immunisation coverage have not been maintained. The objective of this study is to develop a model to estimate the average cost per measles case and per adverse event following measles immunisation using the Netherlands (NL), the United Kingdom (UK) and Canada as examples. METHODS: Parameter estimates were based on a review of the published literature. A decision tree was built to represent the complications associated with measles cases and adverse events following immunisation. Monte-Carlo Simulation techniques were used to account for uncertainty. RESULTS: From the perspective of society, we estimated the average cost per measles case to be US$276, US$307 and US$254 for the NL, the UK and Canada, respectively, and the average cost of adverse events following immunisation per vaccinee to be US$1.43, US$1.93 and US$1.51 for the NL, UK and Canada, respectively. CONCLUSIONS: These average cost estimates could be combined with incidence estimates and costs of immunisation programmes to provide estimates of the cost of measles to industrialised countries. Such estimates could be used as a basis to estimate the potential economic gains of global measles eradication.

Canada↗