The potential impact of an HIV vaccine with limited protection on HIV incidence in Thailand: a modeling study

Background

The RV144 trial on the ALVAC/AIDSVAX candidate HIV vaccine, carried out in Thailand, showed short-lived protection against infection.

Methods

Using a deterministic compartmental model we explored the potential impact of this vaccine on heterosexual HIV transmission in Thailand. Both one-off vaccination strategies, as well as strategies with regular boosting, either annually or every two years, were explored. Both targeting the general adult population and prioritizing sex workers were modeled. The impact of risk compensation among high risk groups, as well as whether higher levels of safe sex in high risk groups could be an alternative to vaccination, was studied.

Results

One-off vaccination campaigns had only transient effects, and boosting appears to be a key component of successful vaccination campaigns. Intensive vaccination campaigns may reduce HIV incidence by up to 75% after 10 years of vaccination. Targeting only sex workers has a smaller impact but has a more favorable cost-benefit ratio. Risk compensation has the potential of undoing much of the benefits of a vaccination program and may even increase incidence. In contrast, higher levels of safe sex among sex workers would provide a viable alternative to vaccinating this group.

Discussion

The new vaccine holds promise for controlling HIV in Thailand and similar countries. In view of the short lived protection of the vaccine, regular boosting of immunity as well as avoidance of risk compensation are essential. Targeting sex workers would achieve the greatest reduction in incidence per vaccination and may be considered for expensive vaccines but its cost-effectiveness has to be compared to alternatives.     

The impact of HIV and AIDS research: a case study from Swaziland

Background

Swaziland is experiencing the world’s worst HIV and AIDS epidemic. Prevalence rose from four percent of antenatal clinic attendees in 1992 to 42.6 percent in 2004. The Report ‘Reviewing ‘Emergencies’ for Swaziland: Shifting the Paradigm in a New Era’ published in 2007 bought together social and economic indicators. It built a picture of the epidemic as a humanitarian emergency, requiring urgent action from international organisations, donors, and governments. Following a targeted communications effort, the report was believed to have raised the profile of the issue and Swaziland - a success story for HIV and AIDS research.

Methods

Keen to understand how, where and why the report had an impact, Health Economics and HIV/AIDS Research Division commissioned an assessment to track and evaluate the influence of the research. This tapped into literature on the significance of understanding the research-to-policy interface. This paper outlines the report and its impact. It explores key findings from the assessment and suggests lessons for future research projects.

Results

The paper demonstrates that, although complex, and not without methodological issues, impact assessment of research can be of real value to researchers in understanding the research-to-policy interface.

Conclusion

Only by gaining insight into this process can researchers move forward in delivering effective research.

     

The impact of population mobility on estimates of environmental exposure effects in a case-control study

In many studies of environmental risk factors for disease, researchers use the location at diagnosis as a geographic reference for environmental exposures. However, many environmental pollutants change continuously over space and time. The dynamic characteristics of these pollutants coupled with population mobility in the United States suggest that for diseases with long latencies like cancer, historic exposures may be more relevant than exposure at the time of diagnosis. In this article, we evaluated to what extent the commonly used assumption of no population mobility results in increased bias in the estimates of the relationship between environmental exposures and long-latency health outcomes disease in a case-control study. We conducted a simulation study using the residential histories of a random sample from the National Institutes of Health-AARP (formerly American Association of Retired Persons) Diet and Health Study. We simulated case-control status based on subject exposure and true exposure effects that varied temporally. We compared estimates from models using only subject location at diagnosis to estimates where subjects were assumed to be mobile. Ignoring population mobility resulted in underestimates of subject exposure, with largest deviations observed at time points further away from study enrollment. In general, the effect of population mobility on the bias of the estimates of the relationship between the exposure and the outcome was more prominent with exposures that showed substantial spatial and temporal variability. Based on our results, we recommend using residential histories when environmental exposures and disease latencies span a long enough time period that mobility is important.     

The rising impact of mathematical modelling in epidemiology: antibiotic resistance research as a case study

Mathematical modelling of infectious diseases has gradually become part of public health decision-making in recent years. However, the developing status of modelling in epidemiology and its relationship with other relevant scientific approaches have never been assessed quantitatively. Herein, using antibiotic resistance as a case study, 60 published models were analysed. Their interactions with other scientific fields are reported and their citation impact evaluated, as well as temporal trends. The yearly number of antibiotic resistance modelling publications increased significantly between 1990 and 2006. This rise cannot be explained by the surge of interest in resistance phenomena alone. Moreover, modelling articles are, on average, among the most frequently cited third of articles from the journal in which they were published. The results of this analysis, which might be applicable to other emerging public health problems, demonstrate the growing interest in mathematical modelling approaches to evaluate antibiotic resistance.     

Potential impact of a maternal vaccine for RSV: A mathematical modelling study

Respiratory syncytial virus (RSV) is a major cause of respiratory morbidity and one of the main causes of hospitalisation in young children. While there is currently no licensed vaccine for RSV, a vaccine candidate for pregnant women is undergoing phase 3 trials. We developed a compartmental age-structured model for RSV transmission, validated using linked laboratory-confirmed RSV hospitalisation records for metropolitan Western Australia. We adapted the model to incorporate a maternal RSV vaccine, and estimated the expected reduction in RSV hospitalisations arising from such a program. The introduction of a vaccine was estimated to reduce RSV hospitalisations in Western Australia by 6–37% for 0–2 month old children, and 30–46% for 3–5 month old children, for a range of vaccine effectiveness levels. Our model shows that, provided a vaccine is demonstrated to extend protection against RSV disease beyond the first three months of life, a policy using a maternal RSV vaccine could be effective in reducing RSV hospitalisations in children up to six months of age, meeting the objective of a maternal vaccine in delaying an infant’s first RSV infection to an age at which severe disease is less likely.     

The impact of HIV/AIDS on Bahamian women: a feminist perspective

The purpose of this article is to describe the impact of HIV/AIDS on Bahamian women and to recommend strategies nurses should implement to enhance the quality of life for these women. Using an eclectic feminist approach, I conducted a literature review and personal exploration of HIV/AIDS care and support related to women as caregivers, care-receivers, childrearers, and childbearers. Women's oppression in a patriarchal society and HIV/AIDS-associated stigmas have resulted in their decreased quality of life and shortened life span. Nurses need to empower Bahamian women and assist with dismantling the social order in The Bahamas, which promotes women's inequality so that women infected with HIV/AIDS can live longer and better lives.     

Reaching the targets for tuberculosis control: the impact of HIV

In 1991, the 44th World Health Assembly set two key targets for global tuberculosis (TB) control to be reached by 2000: 70% case detection of acid-fast bacilli smear-positive TB patients under the DOTS strategy recommended by WHO and 85% treatment success of those detected. This paper describes how TB control was scaled up to achieve these targets; it also considers the barriers encountered in reaching the targets, with a particular focus on how HIV infection affects TB control. Strong TB control will be facilitated by scaling-up WHO-recommended TB/HIV collaborative activities and by improving coordination between HIV and TB control programmes; in particular, to ensure control of drug-resistant TB. Required activities include more HIV counselling and testing of TB patients, greater use and acceptance of isoniazid as a preventive treatment in HIV-infected individuals, screening for active TB in HIV-care settings, and provision of universal access to antiretroviral treatment for all HIV-infected individuals eligible for such treatment. Integration of TB and HIV services in all facilities (i.e. in HIV-care settings and in TB clinics), especially at the periphery, is needed to effectively treat those infected with both diseases, to prolong their survival and to maximize limited human resources. Global TB targets can be met, particularly if there is renewed attention to TB/HIV collaborative activities combined with tremendous political commitment and will.     

Health and economic impact of HIV/AIDS on South African households: a cohort study

Background  

South African households are severely affected by human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) but health and economic impacts have not been quantified in controlled cohort studies.     

The impact of migration on HIV prevention for women: constructing a conceptual framework

There are an estimated 40.5 million people currently living with HIV globally, 17.5 million of whom are women, according to the AIDS Epidemic update: December 2005, conducted by UNAIDS and the World Health Organization (WHO) 2005. Women are vulnerable to HIV for biologic as well as social reasons. In the past, the HIV prevention theorists have not considered the context of women's lives: factors at the individual, relationship, and community levels, as well as structural factors (both policy and cultural) impact on HIV prevention for women. This is particularly true for migrant women, who may be especially vulnerable to HIV infection during their time of transition. Throughout this article I explore the international literature for both the historical context of HIV prevention for women and the impact of migration on HIV risk for women. The literature review provides a basis for the development of a conceptual framework of the socioecologic factors affecting HIV prevention for migrant women. I call for consideration of the broad context of women's experience when developing interventions for this population.     

The changing world of HIV care: The impact on health professionals

Recent advances in treatment have improved the health of many people living with HIV/AIDS. The research described in this paper shows that the changing context of care is also impacting significantly on people who provide services. In this paper, we explore both perspectives by comparing recent service provider data with that derived from research involving people living with HIV/AIDS. We explore four themes: (1) hope and optimism; (2) changing context, roles and identities; (3) changing relationships; and (4) quality of life. Treatment advances and a new focus on living has altered the context of working with people living with HIV/AIDS and challenges health professionals to find new meanings and relationships within that context. Study findings have implications for the wider health care context and the changing roles and power balances within this arena.     

人口流动的分类及其对传染病传播的影响

用文献分析的方法探讨人口流动的相关概念,归纳了人口流动各环节对健康产生的不利影响及国内外对策。提出加强全球合作、加强国境检验检疫、完善医疗保障政策、实施分类管理,健全信息管理体系等防治对策。     

Evaluating the impact of the HIV pandemic on measles control and elimination

OBJECTIVE: To estimate the impact of the HIV pandemic on vaccine-acquired population immunity to measles virus because high levels of population immunity are required to eliminate transmission of measles virus in large geographical areas, and HIV infection can reduce the efficacy of measles vaccination. METHODS: A literature review was conducted to estimate key parameters relating to the potential impact of HIV infection on the epidemiology of measles in sub-Saharan Africa; parameters included the prevalence of HIV, child mortality, perinatal HIV transmission rates and protective immune responses to measles vaccination. These parameter estimates were incorporated into a simple model, applicable to regions that have a high prevalence of HIV, to estimate the potential impact of HIV infection on population immunity against measles. FINDINGS: The model suggests that the HIV pandemic should not introduce an insurmountable barrier to measles control and elimination, in part because higher rates of primary and secondary vaccine failure among HIV-infected children are counteracted by their high mortality rate. The HIV pandemic could result in a 2-3% increase in the proportion of the birth cohort susceptible to measles, and more frequent supplemental immunization activities (SIAs) may be necessary to control or eliminate measles. In the model the optimal interval between SIAs was most influenced by the coverage rate for routine measles vaccination. The absence of a second opportunity for vaccination resulted in the greatest increase in the number of susceptible children. CONCLUSION: These results help explain the initial success of measles elimination efforts in southern Africa, where measles control has been achieved in a setting of high HIV prevalence.     

The impact of needle-exchange programs on the spread of HIV among injection drug users: A simulation study

Objective. To determine the impact of the implementation of a needle-exchange program (NEP) on the spread of human immunodeficiency virus (HIV) in an injection drug user (IDU) community. We conducted a Monte Carlo simulation study of a theoretical population of 10,000 IDUs. The population was followed monthly from 1984 to 2000. HIV was assumed to be transmitted only by needle sharing. The NEP was introduced in 1989 and evaluated over a period of 11 years. The impacts of the proportion of the population attending the NEP, the risk level of IDUs attending the NEP, the reduction in needle-sharing frequency, and the number of new needle-sharing partners acquired at the NEP on prevalence and incidence of HIV were determined. Increasing the proportion of the population who always attend the NEP and eliminating needle-sharing incidents among IDUs who always attended the NEP were the most effective ways of reducing the spread of HIV. Attracting high-risk users instead of lower risk users to the NEP also reduced the spread of HIV, but to a lesser extent. NEPs are effective at reducing the spread of HIV; even under the worst case scenario of low risk users more likely to attend the NEP, one additional partner per month as a result of attending the NEP, and poor NEP attendance, the estimated prevalence was still less than that from the scenario without an NEP. Under our model, NEPs were shown to reduce the spread of HIV significantly. Efforts should be focused on getting as many IDUs as possible to become regular NEP attenders and stop sharing needles rather than partially reducing the frequency of sharing by a larger number of IDUs.     

The impact of sporadic campylobacter and salmonella infection on health and health related behaviour: a case control study

The aim of the work was to explore the impact on general and psychological health of those with a proven bacterial gastrointestinal infection and to compare this with controls from whom no bacterial pathogen was identified. A case control study was conducted using an interviewer-administered questionnaire. Thirty-nine cases from whose faeces salmonella or campylobacter had been cultured were compared with matched controls. Reported gastrointestinal symptoms, general health and self-reported hygiene practices were compared. At the time of acute illness the General Household Questionnaire suggested similar levels of morbidity, though by follow up the controls were substantially more likely to be distressed. Cases were more likely to have changed their food preparation practices, to avoid certain eating places and to have been given advice about food preparation. In this small study a positive diagnosis of salmonella or campylobacter seems to have had a reassuring effect when compared with those for whom no diagnosis was made.     

The impact of endometriosis on early embryo morphokinetics: a case-control study

The aim of this study was to evaluate the possible effects of endometriosis on early embryo development, by comparing the morphokinetic development of embryos obtained from women with clinically confirmed endometriosis with the ones obtained from tubal factor infertility cases. A total of 82 cycles/patients including 53 cycles with endometriosis and 29 cycles with tubal factor infertility were evaluated. A total of 439 embryos were scored for embryo morphokinetics. Age, body mass index, fertilization rates were similar within the groups. However, the number of previous ART trials was found to be higher (p < 0.05) in the study group. Also, the number of retrieved oocytes and M2 oocytes were found to be significantly lower in patients with endometriosis (p < 0.01). The duration of the first cell cycle (ECC1) and S2 (the time between t3 and t4) displayed significant distortions compared with embryos in the control group. All other analyzed early morphokinetic parameters (t2, t3, t4, t5, t6, t7, t8) and duration of events (VP, cc2a, ECC2, ECC3, S3) showed similar values between study and control groups, respectively. In the light of these findings, it is apparent that endometriosis predominantly affects the duration of the early morphokinetic events and cell cycles.     

The methodology of HIV/AIDS impact studies: a review of current practices

This review of studies on the socio-economic impact of HIV/AIDS shows that diversity in methodological design, which often is a result of practical considerations and resource constraints rather than of poor design, is the norm. This limits the comparability of research findings. More detailed reporting on method, which is not the norm, can go some way towards facilitating such comparison. Furthermore, the review underlines the importance of exploring intervention issues in more detail. Researchers need to employ results in answering specific policy questions. Scope remains for more impact studies to be conducted in developing countries in general and in certain high prevalence countries in specific, i.e. Southern Africa. Studies that explore the urban/rural dynamics of and clients' perceptions and behavior in seeking care and support are necessary to better understand the epidemic. The role of community-based organizations, non-governmental organizations and other stakeholders in studies of this nature can be expanded. Larger studies generally have more statistical power, but smaller, in-depth studies can be equally valuable. A careful stratification of sample populations can enhance the quality of cross-sectional studies. Qualitative methods should be used to complement the current reliance on survey-based methods of data collection. More longitudinal studies are required to explore the long-term impacts of HIV/AIDS. HIV/AIDS training for fieldworkers should be standard in studies of this nature, while cognizance should be taken of the dangers of employing local people as fieldworkers in studies of such sensitive nature. Scope remains for the further empirical analysis of data from impact studies, which requires these data sets being made accessible to more researchers. In the longer term, an attempt at standardizing core modules in impact studies can help to improve our understanding of the impact of HIV/AIDS in different settings.     

The social impact of HIV testing: a comparative analysis of Britain and Sweden

The role of HIV testing in the primary prevention of HIV is as yet unclear. Whereas most outcome evaluations have tended to focus on the impact of HIV testing and counselling on individuals' risk behaviours, this paper argues for a fresh perspective on HIV testing which takes into account its social impact. To illustrate the importance of the social impact of HIV testing, the paper compares HIV testing policies in the context of HIV prevention in Britain and in Sweden. It shows how contrasting representations of HIV testing and different practices around testing have had different social, economic and public health consequences in the two countries. The paper concludes with a recommendation that policy makers take fuller account of the social dimension of HIV testing in the future development of HIV testing policies.