The potential epidemiological impact of a genital herpes vaccine for women

An mRNA vaccine to prevent genital herpes

The rapid development of two nucleoside-modified mRNA vaccines that are safe and highly effective against coronavirus disease 2019 has transformed the vaccine field. The mRNA technology has the advantage of accelerated immunogen discovery, induction of robust immune responses, and rapid scale up of manufacturing. Efforts to develop genital herpes vaccines have been ongoing for 8 decades without success. The advent of mRNA technology has the potential to change that narrative. Developing a genital herpes vaccine is a high public health priority. A prophylactic genital herpes vaccine should prevent HSV-1 and HSV-2 genital lesions and infection of dorsal root ganglia, the site of latency. Vaccine immunity should be durable for decades, perhaps with the assistance of booster doses. While these goals have been elusive, new efforts with nucleoside-modified mRNA-lipid nanoparticle vaccines show great promise. We review past approaches to vaccine development that were unsuccessful or partially successful in large phase 3 trials, and describe lessons learned from these trials. We discuss our trivalent mRNA-lipid nanoparticle approach for a prophylactic genital herpes vaccine and the ability of the vaccine to induce higher titers of neutralizing antibodies and more durable CD4+ T follicular helper cell and memory B cell responses than protein-adjuvanted vaccines.

Computational and Theoretical Analysis of the Association Between Gender and HSV-2 Treatment Adherence

Herpes simplex virus type 2 (HSV-2) is the most prevalent sexually transmitted infection in the world, despite the availability of effective anti-viral treatments. A mathematical model to explore the association between gender and HSV-2 treatment adherence is developed. Threshold parameters are determined and stabilities analyzed. Sensitivity analysis of the reproduction number and the numerical simulations suggest that treatment adherence for both females and males are equally important in keeping the reproduction as low as possible. The basic model is then extended to incorporate time-dependent intervention strategies. The Pontryagin's Maximum Principle is used to characterize the optimal level of the controls, and the resulting optimality system is solved numerically.

Antiviral therapy for the sexually transmitted viruses: recent updates on vaccine development

INTRODUCTION

The sexually transmitted infections (STIs) caused by viruses including human T cell leukemia virus type-1 (HTLV-1), human immunodeficiency virus-1 (HIV-1), human simplex virus-2 (HSV-2), hepatitis C virus (HCV), hepatitis B virus (HBV), and human papillomavirus (HPV) are major public health issues. These infections can cause cancer or result in long-term health problems. Due to high prevalence of STIs, a safe and effective vaccine is required to overcome these fatal viruses.

AREAS COVERED

This review includes a comprehensive overview of the literatures relevant to vaccine development against the sexually transmitted viruses (STVs) using PubMed and Sciencedirect electronic search engines. Herein, we discuss the efforts directed toward development of effective vaccines using different laboratory animal models including mice, guinea pig or non-human primates in preclinical trials, and human in clinical trials with different phases.

EXPERT OPINION

There is no effective FDA approved vaccine against the sexually transmitted viruses (STVs) except for HBV and HPV as prophylactic vaccines. Many attempts are underway to develop vaccines against these viruses. There are several approaches for improving prophylactic or therapeutic vaccines such as heterologous prime/boost immunization, delivery system, administration route, adjuvants, etc. In this line, further studies can be helpful for understanding the immunobiology of STVs in human. Moreover, development of more relevant animal models is a worthy goal to induce effective immune responses in humans.

Epidemiological Impact of Novel Preventive and Therapeutic HSV-2 Vaccination in the United States: Mathematical Modeling Analyses

This study aims to inform herpes simplex virus type 2 (HSV-2) vaccine development, licensure, and implementation by delineating the population-level impact of vaccination. Mathematical models were constructed to describe the transmission dynamics in presence of prophylactic or therapeutic vaccines assuming 50% efficacy, with application to the United States. Catch-up prophylactic vaccination will reduce, by 2050, annual number of new infections by 58%, incidence rate by 60%, seroprevalence by 21%, and avert yearly as much as 350,000 infections. Number of vaccinations needed to avert one infection was only 50 by 2050, 34 by prioritizing those aged 15-19 years, 4 by prioritizing the highest sexual risk group, 43 by prioritizing women, and 47 by prioritizing men. Therapeutic vaccination of infected adults with symptomatic disease will reduce, by 2050, annual number of new infections by 12%, incidence rate by 13%, seroprevalence by 4%, and avert yearly as much as 76,000 infections. Number of vaccinations needed to avert one infection was eight by 2050, two by prioritizing those aged 15-19 years, three by prioritizing the highest sexual risk group, seven by prioritizing men, and ten by prioritizing women. HSV-2 vaccination offers an impactful and cost-effective intervention to prevent genital herpes medical and psychosexual disease burden.

Dynamics of HSV-2 infection with a therapeutic vaccine

Herpes-Simplex Virus type 2 (HSV-2) is a lifelong infection, which has infected over 400 million individuals aged 15-49 years, worldwide. While the disease can be treated with episodic and suppressive antiviral drugs to reduce the rate of recurrence (i.e., symptomatic disease) and viral shedding, none of the currently available therapies can clear the virus from the body of an infected person. A number of therapeutic vaccine platforms are currently in development in order to achieve similar effects to treatment. Due to the inadequate data from clinical trials of therapeutic vaccines, modeling efforts to quantify the impact of vaccination have been limited. In this study, we propose a compartmental deterministic model for the dynamics of HSV-2 to evaluate the effect of a potential vaccine candidate with the inclusion of a booster dose. Despite its simplicity that may not address the complexity of HSV-2 disease, the model shows that targeting symptomatic infection for vaccination is the most effective strategy in the long-term. This conclusion is based on the assumption of an optimal vaccine efficacy, conferring immunity levels that prevent viral shedding and recurrence transiently. Our model provides a framework for developing a computational system to include more heterogeneous characteristics of the disease and individuals, and investigate effectiveness and cost-effectiveness of vaccination scenarios when clinical data become available.

Modelling efforts needed to advance herpes simplex virus (HSV) vaccine development: Key findings from the World Health Organization Consultation on HSV Vaccine Impact Modelling

Development of a vaccine against herpes simplex virus (HSV) is an important goal for global sexual and reproductive health. In order to more precisely define the health and economic burden of HSV infection and the theoretical impact and cost-effectiveness of an HSV vaccine, in 2015 the World Health Organization convened an expert consultation meeting on HSV vaccine impact modelling. The experts reviewed existing model-based estimates and dynamic models of HSV infection to outline critical future modelling needs to inform development of a comprehensive business case and preferred product characteristics for an HSV vaccine. This article summarizes key findings and discussions from the meeting on modelling needs related to HSV burden, costs, and vaccine impact, essential data needs to carry out those models, and important model components and parameters.

Review of mathematical models of HSV-2 vaccination: Implications for vaccine development

Development of a vaccine against herpes simplex virus type 2 (HSV-2), a life-long sexually-transmitted infection (STI), would be a major step forward in improving global sexual and reproductive health. In this review, we identified published literature of dynamic mathematical models assessing the impact of either prophylactic or therapeutic HSV-2 vaccination at the population level. We compared each study's model structure and assumptions as well as predicted vaccination impact. We examined possible causes of heterogeneity across model predictions, key gaps, and the implications of these findings for future modelling efforts. Only eight modelling studies have assessed the potential public health impact of HSV-2 vaccination, with the majority focusing on impact of prophylactic vaccines. The studies showed that even an imperfect prophylactic HSV-2 vaccine could have an important public health impact on HSV-2 incidence, and could also impact HIV indirectly in high HIV prevalence settings. Therapeutic vaccines also may provide public health benefits, though they have been explored less extensively. However, there was substantial variation in predicted population-level impact for both types of vaccine, reflecting differences in assumptions between model scenarios. Importantly, many models did not account for heterogeneity in infection rates such as by age, sex and sexual activity. Future modelling work to inform decisions on HSV vaccine development and implementation should consider cost-effectiveness, account for additional HSV-2 sequelae such as neonatal transmission, and model greater heterogeneity in infection rates between individuals, more realistic vaccine deployment, and more thorough sensitivity and uncertainty analyses.

The potential of currently unavailable herpes virus vaccines

INTRODUCTION

Despite overwhelming experimental work, there are no licensed vaccines against the most frequent Alphaherpesviruses, namely herpes simplex virus 1 and 2 (HSV1 and 2) nor against the Epstein-Barr virus (EBV), a member of the subfamily Gammaherpesvirus.

AREAS COVERED

Since the DNAs of both HSVs reside in the regional sensory ganglia in a latent state (i.e. as circularized episomal molecules), a corresponding vaccine might be useful for immunotherapy rather than for prevention of primary infection. Here we describe the design of a purified subunit vaccine as well as the preparation and efficacy of a recombinant fusion protein consisting of the gD ectodomain from our domestic attenuated HSV1 strain HSZP. The EBV vaccines considered so far, were destined for prevention of infectious mononucleosis (IM) or to prevent formation of EBV related tumors. To design the EBV peptide vaccine, at least 15 carefully selected immunogenic epitopes coming from 12 virus coded proteins were bound to synthetic micro-particle carriers along with a non-specific pathogen recognizing receptor (PRR) stimulating both the T as well as B lymphocytes.

EXPERT COMMENTARY

The efficacy of a novel EBV peptide in the rabbit model was based on criteria such as antibody formation (EA-D detected by ELISA, early and capsid proteins tested by immunoblot), presence of LMP1 antigen and of viral DNA in peripheral white blood cells. Out of 19 peptide combinations used for vaccination, at least 6 showed a satisfactory protective effect.

Seroprevalence of Herpes Simplex Virus Type 1 and Type 2 and Coinfection With HIV and Syphilis: The First National Seroprevalence Survey in Saudi Arabia

BACKGROUND

Herpes simplex virus (HSV) infection is one of the most common viral infections worldwide. Genital herpes is associated with other sexually transmitted infections (STIs) including HIV. Data on prevalence of HSV infections and other STIs in the Kingdom of Saudi Arabia are limited.

METHODS

We conducted the first national seroprevalence survey to determine the prevalence and epidemiology of HSV infection among adult Saudis and coinfection with other STIs. Serology was used to detect HSV-1, HSV-2, HIV, and syphilis infections among 4985 participants recruited from across the Kingdom.

RESULTS

The overall prevalence of HSV-1 and HSV-2 in the enrolled population was 88.8% and 1.26%, respectively. Although not significant for HSV-2, HSV infection was more prevalent among females, those working, and those who were married (married, divorced, or widowed), especially those married at a younger age. Prevalence of both viruses was statistically significantly higher among those with low education and increased with age. Prevalence of Treponema pallidum antibodies and HIV in the sampled population was very low (0.55% and 0.06%, respectively), as was their prevalence among HSV-2-positive participants (1.6% for both). The correlation between HSV-2 infection and other STIs was significant for HIV (P < 0.0001) but not for T. pallidum antibodies (P = 0.25).

CONCLUSIONS

Herpes simplex virus type 1 infection is highly prevalent in Saudi Arabia and mostly acquired before adulthood. Herpes simplex virus type 2 prevalence is very low, acquired in adulthood, and increased with age. Monitoring the prevalence of HSV infection can help inform targeted strategies to prevent new infections, neonatal transmission, and the spread of other STIs in the Kingdom.

The theoretical impact and cost-effectiveness of vaccines that protect against sexually transmitted infections and disease

Sexually transmitted diseases, a source of widespread morbidity and sometimes mortality, are caused by a diverse group of infections with a common route of transmission. Existing vaccines against hepatitis B virus (HBV) and human papilloma virus 16, 18, 6 and 11 are highly efficacious and cost effective. In reviewing the potential role for other vaccines against sexually transmitted infections (STIs) a series of questions needs to be addressed about the burden of disease, the potential characteristics of a new vaccine, and the impact of other interventions. These questions can be viewed in the light of the population dynamics of sexually transmitted infections as a group and how a vaccine can impact these dynamics. Mathematical models show the potential for substantial impact, especially if vaccines are widely used. To better make the case for sexually transmitted infection vaccines we need better data and analyses of the burden of disease, especially severe disease. However, cost effectiveness analyses using a wide range of assumptions show that STI vaccines would be cost effective and their development a worthwhile investment.

Prevalence of herpes simplex virus type 2 and risk factors associated with this infection in women in southern Brazil

SUMMARY

The herpes simplex virus type 2 (HVS-2) is the most prevalent infection worldwide. It is a cofactor in the acquisition of human immunodeficiency virus (HIV) and the persistence of human papillomavirus (HPV). This study evaluated the prevalence of HSV-2, using the polymerase chain reaction (PCR), and associated factors in patients treated at the Federal University of Rio Grande (FURG) and Basic Health Units (BHU) in Rio Grande, Brazil. The observed prevalence of HSV-2 was 15.6%. Among the 302 women studied, 158 had received assistance in BHU and 144 were treated at FURG. The prevalence of HSV-2 in these groups was 10.8% and 20.8%, respectively, RR 1.9 and p = 0.012. Knowledge about the Pap smear, and the presence of lesions showed no association with HSV-2 infection. Multivariate analysis showed that the variable that most influenced the risk of HSV-2 infection was the presence of HIV infection, with a relative risk of 1.9 and p = 0.04. Discussion: Genital ulcers are an important entry point for HIV, and condom use is an important strategy to reduce transmission of HIV and HSV-2.

Current status and prospects for development of an HSV vaccine

Herpes simplex virus type 2 (HSV-2) infects 530million people, is the leading cause of genital ulcer disease, and increases the risk of HIV-1 acquisition. Although several candidate vaccines have been promising in animal models, prophylactic and therapeutic vaccines have not been effective in clinical trials thus far. Null results from the most recent prophylactic glycoprotein D2 subunit vaccine trial suggest that we must reevaluate our approach to HSV-2 vaccine development. We discuss HSV-2 pathogenesis, immunity, and vaccine efforts to date, as well as the current pipeline of candidate vaccines and design of trials to evaluate new vaccine constructs.

Varicella zoster vaccines and their implications for development of HSV vaccines

Live attenuated vaccines to prevent varicella and zoster have been available in the US for the past 17 years, with a resultant dramatic decrease in varicella incidence and a predicted future decrease in the incidence of zoster. The pathogenesis and immune responses to varicella zoster virus (VZV) as well as the safety and effectiveness of VZV vaccines are reviewed. The lack of sterilizing immunity provided by VZV vaccines has not prevented them from being safe and effective. Virological and pathological information concerning parallels and differences between VZV and herpes simplex virus (HSV) are highlighted. Although VZV and HSV are distinct pathogens, they appear to have similarities in target organs and immunity that provide an expectation of a high likelihood for the success of vaccination against HSV, and predicted to be similar to that of VZV.

Epidemiological impact of a genital herpes type 2 vaccine for young females

Genital Herpes, which is caused by Herpes Simplex Virus-1 or -2 (HSV-1, -2, predominantly HSV-2) is a sexually transmitted infection (STI) that causes a chronic latent infection with outbreak episodes linked to transmission. Antiviral therapies are effective in reducing viral shedding during these episodes, but are ineffective as a whole since many outbreaks are asymptomatic or have mild symptoms. Thus, the development of a vaccine for genital herpes is needed to control this disease. The question of how to implement such a vaccine program is an important one, and may be similar to the vaccination program for Human Papilloma Virus (HPV) for young females. We have developed a mathematical model to describe the epidemiology of vaccination targeting young females against HSV-2. The model population is delineated with respect to age group, sexual activity and infection status including oral infection of HSV-1, which may affect vaccine efficacy. A threshold parameter R(C), which determines the level of vaccine uptake needed to eradicate HSV-2, is found. Computer simulation shows that an adolescent-only vaccination program may be effective in eliminating HSV-2 disease, however, the success of extinction greatly depends on the level of vaccine uptake, the vaccine efficacy, the age of sexual maturity and safe sex practices. However, the time course of eradication would take many years. We also investigate the prevalence of infection in the total population and in women between 16-30 years of age before and after vaccination has been introduced, and show that the adolescent-only vaccination program can be effective in reducing disease prevalence in these populations depending on the level of vaccine uptake and vaccine efficacy. This will also result in a decrease of maternal-fetal transmission of HSV-2 infection. Another important, if commonsense, conclusion is that vaccination of some females reduces infection in men, which then reduces infection in women.

A Vaxfectin(®)-adjuvanted HSV-2 plasmid DNA vaccine is effective for prophylactic and therapeutic use in the guinea pig model of genital herpes

Here we describe studies in the guinea pig model of genital herpes to evaluate a novel plasmid DNA (pDNA) vaccine encoding the HSV-2 glycoprotein D and UL46 and UL47 genes encoding tegument proteins VP11/12 and VP 13/14 (gD2/UL46/UL47), formulated with a cationic lipid-based adjuvant Vaxfectin(®). Prophylactic immunization with Vaxfectin(®)-gD2/UL46/UL47 significantly reduced viral replication in the genital tract, provided complete protection against both primary and recurrent genital skin disease following intravaginal HSV-2 challenge, and significantly reduced latent HSV-2 DNA in the dorsal root ganglia compared to controls. We also examined the impact of therapeutic immunization of HSV-2 infected animals. Here, Vaxfectin(®)-gD2/UL46/UL47 immunization significantly reduced both the frequency of recurrent disease and viral shedding into the genital tract compared to controls. This novel adjuvanted pDNA vaccine has demonstrated both prophylactic and therapeutic efficacy in the guinea pig model of genital herpes and warrants further development.

Towards a rational design of an asymptomatic clinical herpes vaccine: the old, the new, and the unknown

The best hope of controlling the herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) pandemic is the development of an effective vaccine. However, in spite of several clinical trials, starting as early as 1920s, no vaccine has been proven sufficiently safe and efficient to warrant commercial development. In recent years, great strides in cellular and molecular immunology have stimulated creative efforts in controlling herpes infection and disease. However, before moving towards new vaccine strategy, it is necessary to answer two fundamental questions: (i) why past herpes vaccines have failed? (ii) Why the majority of HSV seropositive individuals (i.e., asymptomatic individuals) are naturally "protected" exhibiting few or no recurrent clinical disease, while other HSV seropositive individuals (i.e., symptomatic individuals) have frequent ocular, orofacial, and/or genital herpes clinical episodes? We recently discovered several discrete sets of HSV-1 symptomatic and asymptomatic epitopes recognized by CD4(+) and CD8(+) T cells from seropositive symptomatic versus asymptomatic individuals. These asymptomatic epitopes will provide a solid foundation for the development of novel herpes epitope-based vaccine strategy. Here we provide a brief overview of past clinical vaccine trials, outline current progress towards developing a new generation "asymptomatic" clinical herpes vaccines, and discuss future mucosal "asymptomatic" prime-boost vaccines that could optimize local protective immunity.

Expression of recombinant herpes simplex virus type 2 glycoprotein D by high-density cell culture of Spodoptera frugiperda

Herpes simplex virus type 2 (HSV-2) is the major cause of genital herpes in humans. The glycoprotein D of HSV-2 (gD2) is a promising subunit vaccine candidate for the treatment of genital herpes. The aim of the present study was to express a biologically active recombinant gD2 in eukaryotic baculovirus system in quantities sufficient for further studies. Human cDNA encoding a gD2 protein with 393 amino acids was subcloned into the pFastBac HTb vector and the recombinant protein was expressed in Spodoptera frugiperda (Sf9) cells by high-density cell culture. In a stirred bioreactor, the key limiting factors including glucose concentration, glutamine concentration and dissolved oxygen (DO) were optimized for high-density cell growth. The Sf9 cell density could reach 9.6×10⁶ cells/mL and the yield of recombinant gD2 protein was up to 192 mg/L in cell culture under the optimal conditions of 15 mM glucose, 0.4 g/L glutamine and 40% DO. Production of significant amounts of pure, full-length gD2 opened up the possibility to investigate novel functions of gD2. Moreover, the purified recombinant gD2 protein revealed a partial prophylactic immune function in genital herpes of guinea pigs infected with HSV-2.

HSV-2: in pursuit of a vaccine

Herpes simplex virus type 2 (HSV-2) is one of the most prevalent sexually transmitted infections worldwide. In addition to recurrent genital ulcers, HSV-2 causes neonatal herpes, and it is associated with a 3-fold increased risk for HIV acquisition. Although many HSV-2 vaccines have been studied in animal models, few have reached clinical trials, and those that have been tested in humans were not consistently effective. Here, we review HSV-2 pathogenesis, with a focus on novel understanding of mucosal immunobiology of HSV-2, and vaccine efforts to date, in an attempt to stimulate thinking about future directions for development of effective prophylactic and therapeutic HSV-2 vaccines.

Herpes simplex virus infection in the Croatian population

BACKGROUND

Herpes simplex virus (HSV) infections are caused by 2 types of virus, HSV-1 and HSV-2. Both viruses are endemic worldwide. There are marked variations in the seroprevalences of HSV-1 and HSV-2 in Europe. The aim of this study was to determine the seroprevalence of HSV infections in Croatia.

METHODS

During a 3-y period (2008-2010), a total of 1672 patients were tested for the presence of HSV-1 and HSV-2 antibodies using an enzyme-linked immunosorbent assay.

RESULTS

The overall immunoglobulin G (IgG) seroprevalence rates were 72.5% for HSV-1 and 9.9% for HSV-2. There was no significant difference in seropositivity between males and females for HSV-1 (72.0% vs 73.0%) or HSV-2 (8.9% vs 10.7%). HSV-1 seroprevalence increased from 26.4% in those aged 6 months-9 y to 89.9% in those aged 40?49 y, and remained stable thereafter, ranging from 87.4% to 91.5% (p < 0.001). HSV-2 IgG seropositivity increased progressively from 5.7% in participants aged 20-29 y to 26.5% in participants aged ≥ 60 y (p < 0.001). HSV-1 seroprevalence did not differ between participants residing in urban and rural areas (72.5% vs 72.6%). Urban place of residence was a significant factor for HSV-2 seroprevalence in univariate analysis, but after standardization for age, it was no longer significant.

CONCLUSIONS

Multiple logistic regression showed that age was a significant predictor of both HSV-1 and HSV-2 seropositivity, while female gender was a significant predictor of HSV-2 seropositivity. In pregnant women, obstetric history was not a significant predictor of either HSV-1 or HSV-2 seroprevalence.

Soroprevalência de anticorpos contra vírus herpes simples 1-2 no Brasil

OBJETIVO: Estimar a soroprevalência de anticorpos por vírus herpes simples (HSV-1 e HSV-2) e analisar fatores associados no Brasil. MÉTODOS: Estudo transversal realizado entre 1996 e 1997 em 1.090 indivíduos com idade entre um e 40 anos da população geral, em quatro diferentes regiões geográficas no Brasil. Foram analisadas amostras sangüíneas para detecção de anticorpos para HSV-1 e HSV-2 com teste tipo-específico Elisa. Foram descritas freqüências e proporções, comparadas entre grupos utilizando o teste de Fisher bilateral exato. Foi realizada análise de regressão logística para avaliar influência das variáveis sociodemográficas e histórico de DST, sobre a soroprevalência de HSV-1 e/ou HSV-2. RESULTADOS: As soroprevalências de anticorpos para HSV-1 e HSV-2, ajustadas por idade, foram 67,2% e 11,3% respectivamente, sem diferença quanto ao sexo e maiores na Região Norte. As soroprevalências aumentaram com a idade, e para HSV-2 o maior aumento ocorreu na adolescência e entre adultos jovens. Indivíduos soropositivos para HSV-1 apresentaram maior risco de serem positivos para HSV-2 (15,7%) quando comparados com os negativos para HSV-1 (4,7%). Na análise multivariada, o histórico de DST aumentou significativamente (OR=3,2) a probabilidade de soropositividade para HSV-2. CONCLUSÕES: As soroprevalências para HSV-1 e para HSV-2 variam com a idade e entre as regiões do Brasil. História pregressa de DST é importante fator de risco para aquisição de infecção por HSV-2.

Protection from herpes simplex virus (HSV)-2 infection with replication-defective HSV-2 or glycoprotein D2 vaccines in HSV-1-seropositive and HSV-1-seronegative guinea pigs

BACKGROUND

A herpes simplex virus (HSV)-2 candidate vaccine consisting of glycoprotein D (gD2) in alum and monophosphoryl lipid A (MPL) reduced genital herpes disease in HSV-1-seronegative women but not in men or HSV-1-seropositive women.

METHODS

To determine the effect of HSV-1 serostatus on effectiveness of different vaccines, we tested gD2 in alum/MPL, gD2 in Freund's adjuvant, and dl5-29 (a replication-defective HSV-2 mutant) in HSV-1-seropositive or HSV-1-seronegative guinea pigs.

RESULTS

In HSV-1-seronegative animals, dl5-29 induced the highest titers of neutralizing antibody, and after vaginal challenge with wild-type virus, dl5-29 resulted in lower rates of vaginal shedding, lower levels of HSV DNA in ganglia, and a trend for less acute and recurrent genital herpes, compared with the gD2 vaccines. In HSV-1-seropositive animals, all 3 vaccines induced similar titers of neutralizing antibodies and showed similar levels of protection against acute and recurrent genital herpes after vaginal challenge with wild-type virus, but dl5-29 reduced vaginal shedding after challenge more than did the gD2 vaccines.

CONCLUSIONS

dl5-29 Is an effective vaccine in both HSV-1-seropositive and HSV-1-seronegative guinea pigs and was superior to gD2 vaccines in reducing virus shedding after challenge in both groups of animals. dl5-29 Might reduce transmission of HSV-2.

Estradiol improves genital herpes vaccine efficacy in mice

Herpes Simplex Virus type 2 causes genital herpes but is frequently transmitted asymptomatically; therefore, a prophylactic vaccine is desirable. A candidate vaccine in clinical trials has only shown efficacy in preventing disease in women. Using this subunit vaccine candidate, we were able to demonstrate infection prophylaxis, improved disease prevention and modulated antibody production by complimenting vaccination with estradiol in our murine model. Findings of estradiol-enhanced vaccine efficacy are the first of their kind using a vaccine of this type and have potential clinical relevance to the development of other vaccines and our understanding of gender differences in vaccine efficacy.

[Experimental vaccines for sexually transmitted infections]

INTRODUCTION

Sexually transmitted infections (STIs) are major global public health problems. Present strategies for prevention have limitations. Vaccines are an attractive addition to the current prevention armamentarium because they provide durable protection and do not require repetitive adherence to be effective. Challenges for vaccination include induction and long-term maintenance of mucosal immune responses in the female genital tract.

VACCINES

A REALISTIC GOAL? For the time being, US Centers for Disease Control and Prevention have recommended only hepatitis and HPV immunization to be routinely offered. Final, III stage trials are underway on other prophylactic vaccines for human papillomavirus and genital herpes. Though vaccines against Chlamydia trachomatis and Neisseria gonorrhoeae are in early stages of development they do offer the hope of preventing pelvic inflammations. The high incidence of HIV-infection for which a vaccine would not be readily available, "cries out" for an effective vaccine.

VACCINES FOR HPV INFECTIONS

According to a recent meta-analysis of worldwide prevalence data, vaccinating with HPV-16/18 VLP against HPV-16 and HPV-18 could prevent over 70% of invasive cervical cancer worldwide. The latest release of data from the phase III trial of a quadrivalent recombinant non-infectious vaccine HPV-6/11/16/18 L1 VLP, including HPV types 6, 11, 16, 18 have given complete protection against HPV-16/18-related cervical intraepithelial neoplasias 1, 2/3, and adenocarcinoma in situ and cancer through 2 years of post-vaccination follow up.

CONCLUSION

Despite the fact that the development of vaccines for STI prevention was rather slow in the past, the ideal vaccine would decrease transmission of the infection between partners and would prevent complications of disease. Moreover, in future decades, increasingly successful universal vaccination of newborns and children will substantially reduce the need for vaccination of persons with specific risk factors, including sexual risk.

Dynamic modeling of herpes simplex virus type-2 (HSV-2) transmission: issues in structural uncertainty

The sexually transmitted infection (STI) Herpes simplex virus type-2 (HSV-2) is of public health concern because it is a very common frequently unrecognized lifelong infection, which may facilitate HIV transmission. Within HIV/STI modeling, structural uncertainty has received less attention than parametric uncertainty. By merging the compartments of a "complex" model, a "simple" HSV-2 model is developed. Sexual interactions between female sex workers (FSWs) and clients are modeled using data from India. Latin Hypercube Sampling selects from parameter distributions and both models are run for each of the 10,000 parameter sets generated. Outputs are compared (except for 2,450 unrealistic simulations). The simple model is a good approximation to the complex model once the HSV-2 epidemic has reached 60% of the equilibrium prevalence (95% of the 7,550 runs produced <10% relative error). The simple model is a reduced version of the complex model that retains details implicitly. For late-stage epidemics, the simple model gives similar prevalence trends to the complex model. As HSV-2 epidemics in many populations are advanced, the simple model is accurate in most instances, although the complex model may be preferable for early epidemics. The analysis highlights the issue of structural uncertainty and the value of reducing complexity.

Population-level effect of potential HSV2 prophylactic vaccines on HIV incidence in sub-Saharan Africa

Herpes simplex virus type-2 (HSV2) infection increases HIV transmission. We explore the impact of a potential prophylactic HSV2 vaccination on HIV incidence in Africa using STDSIM an individual-based model. A campaign that achieved 70% coverage over 5 years with a vaccine that reduced susceptibility to HSV2 acquisition and HSV2 reactivation by 75% for 10 years, reduced HIV incidence by 30-40% after 20 years (range 4-66%). Over 20 years, in most scenarios fewer than 100 vaccinations were required to avert one HIV infection. HSV2 vaccines could have a substantial impact on HIV incidence. Intensified efforts are needed to develop an effective HSV2 vaccine.

An estimate of the global prevalence and incidence of herpes simplex virus type 2 infection

OBJECTIVE

To estimate the global prevalence and incidence of herpes simplex virus type 2 (HSV-2) infection in 2003.

METHODS

A systematic review was undertaken of published seroprevalence surveys describing the prevalence or incidence of HSV-2 by age and gender. For each of 12 regions, pooled prevalence values by age and gender were generated in a random-effect model. HSV-2 incidence was then estimated from these pooled values using a constant-incidence model. Values of the HSV-2 seroprevalence from the model fits were applied to the total population to estimate the numbers of people infected.

FINDINGS

The total number of people aged 15-49 years who were living with HSV-2 infection worldwide in 2003 is estimated to be 536 million, while the total number of people who were newly infected with HSV-2 in 2003 is estimated to be 23.6 million. While the estimates are limited by poor availability of data, general trends are evident. For example, more women than men were infected, and the number infected increased with age. Although prevalence varied substantially by region, predicted prevalence was mostly higher in developing regions than developed regions.

CONCLUSION

The prevalence of HSV-2 is relatively easy to measure since infection is lifelong and has a specific serological test. The burden of disease is less easy to quantify. Despite the often sparse data on which these estimates are based, it is clear that HSV-2 infection is widespread. The dramatic differences in prevalence between regions are worthy of further exploration.

Glycoprotein D adjuvant herpes simplex virus vaccine

Herpes simplex virus (HSV) Type-1 and -2 are common infections that can cause primary and recurrent herpes labialis and genitalis, as well as gingivostomatitis, keratoconjunctivitis, encephalitis, disseminated infections in immunocompromised persons and neonatal infections. Despite several decades of HSV vaccine development, no effective vaccine has been developed until recently. The following review of the genital HSV-2 glycoprotein D (gD2t, t is for truncated) subunit vaccine formulated with a new adjuvant (AS04) containing alum and 3-O deacylated monophosphoryl lipid A (MPL) provides a background in which to evaluate the vaccine as well as a brief review of other approaches to herpes vaccines. The gD2t-AS04 vaccine has been demonstrated to be safe in several large clinical trials. In two trials, the vaccine reduced genital herpes disease by 73 and 74%, but only in females with no previous HSV infection. A large ongoing trial in HSV seronegative females will provide additional data on protection from HSV disease and infection.

Incident and prevalent herpes simplex virus type 2 infection increases risk of HIV acquisition among women in Uganda and Zimbabwe

BACKGROUND

An association has been demonstrated between herpes simplex type 2 (HSV-2) and HIV infection among men, but prospective studies in women have yielded mixed results.

OBJECTIVE

To estimate the effects of prevalent and incident HSV-2 infection on subsequent HIV acquisition among women in two African countries.

DESIGN

Prospective cohort study.

METHODS

HSV-2 and HIV serostatus were evaluated at enrollment and quarterly for 15-24 months among 4531 sexually active, HIV-uninfected women aged 18-35 years from Uganda and Zimbabwe. The association between prior HSV-2 infection and HIV acquisition was estimated using a marginal structural discrete survival model, adjusted for covariates.

RESULTS

HSV-2 seroprevalence at enrollment was 52% in Uganda and 53% in Zimbabwe; seroincidence during follow-up was 9.6 and 8.8/100 person-years in Uganda and Zimbabwe, respectively. In Uganda, the hazard ratio (HR) for HIV was 2.8 [95% confidence interval (CI), 1.5-5.3] among women with seroprevalent HSV-2 and 4.6 (95% CI, 1.6-13.1) among women with seroincident HSV-2, adjusted for confounding. In Zimbabwe, the HR for HIV was 4.4 (95% CI, 2.7-7.2) among women with seroprevalent HSV-2, and 8.6 (95% CI, 4.3-17.1) among women with seroincident HSV-2, adjusted for confounding. The population attributable risk percent for HIV due to prevalent and incident HSV-2 infection was 42% in Uganda and 65% in Zimbabwe.

CONCLUSIONS

HSV-2 plays an important role in the acquisition of HIV among women. Efforts to implement known HSV-2 control measures, as well as identify additional measures to control HSV-2, are urgently needed to curb the spread of HIV.

Suppressive Valacyclovir Therapy: Impact on the Population Spread of HSV-2 Infection

OBJECTIVES

Recent trial results demonstrate that the transmission probability of HSV-2 in monogamous couples is nearly halved by the use of valacyclovir as suppressive therapy.

GOAL

The goal of this study is to understand the potential impact of suppressive valacyclovir therapy on the transmission of HSV-2 within a population.

STUDY DESIGN

A mathematical model of HSV-2 epidemiology was developed which included suppressive therapy with the efficacy observed in the clinical trial. The model represented HSV-2 spread in an age and sexual activity stratified population where rates of viral shedding declined based on time since infection. The model tested the impact of a range of suppression coverage levels.

RESULTS

Suppressive therapy reduces the population incidence of HSV-2. With coverage rates of 3.2%, the incidence of HSV-2 would be reduced by between 1.8% and 2.8%. Higher coverage rates were estimated to reduce the incidence of new cases up to 13%. Starting suppression closer to the time of infection also reduces the incidence of new cases.

CONCLUSION

The impact of suppressive therapy on the HSV-2 epidemic is modest at current coverage levels but could be substantially increased with higher rates of diagnosis and a focus on coverage soon after infection.

Quantification of poly(I:C)-mediated protection against genital herpes simplex virus type 2 infection

Alternative strategies for controlling the growing herpes simplex virus type 2 (HSV-2) epidemic are needed. A novel class of immunomodulatory microbicides has shown promise as antiherpetics, including intravaginally applied CpG-containing oligodeoxynucleotides that stimulate toll-like receptor 9 (TLR9). In the current study, we quantified protection against experimental genital HSV-2 infection provided by an alternative nucleic acid-based TLR agonist, polyinosine-poly(C) (PIC) (TLR3 agonist). Using a protection quantification paradigm, groups of mice were PIC treated and then subdivided into groups challenged with escalating doses of HSV-2. Using this paradigm, a temporal window of PIC efficacy for single applications was defined as 1 day prior to (prophylactic) through 4 h after (therapeutic) viral challenge. PIC treatment within this window protected against 10-fold-higher HSV-2 challenges, as indicated by increased 50% infectious dose values relative to those for vehicle-treated controls. Disease resolution and survival were significantly enhanced by repetitive PIC doses. Using optimal PIC regimens, cytokine induction was evaluated in murine vaginal lavages and in human vaginal epithelial cells. Similar induction patterns were observed, with kinetics that explained the limited durability of PIC-afforded protection. Daily PIC delivery courses did not generate sustained cytokine levels in murine vaginal fluids that would be indicative of local immunotoxicity. No evidence of immunotoxicity was observed in selected organs that were analyzed following repetitive vaginal PIC doses. Animal and in vitro data indicate that PIC may prove to be a valuable preventative microbicide and/or therapeutic agent against genital herpes by increasing resistance to HSV-2 and enhancing disease resolution following a failure of prevention.

Strategies for global HIV prevention

Despite significant advances in the development of therapeutic strategies for HIV over the past 25 years, the AIDS pandemic continues to grow worldwide. Access to life-saving medicines is not universal and there is a critical need for better prevention strategies. This review will highlight current research in the area of HIV prevention strategies, including preventive HIV vaccines, effective microbicides, treatment of sexually transmitted infections and the impact on HIV transmission, in addition to the role of male circumcision and pre-exposure prophylaxis with antiretroviral medications in HIV prevention.

Developments in herpes simplex virus vaccines: old problems and new challenges

Vaccination has remained the best method for preventing virus spread. The herpes simplex virus (HSV) candidate vaccines tested till now were mostly purified subunit vaccines and/or recombinant envelope glycoproteins (such as gB and gD). In many experiments performed in mice, guinea pigs and rabbits, clear-cut protection against acute virus challenge was demonstrated along with the reduction of the extent of latency, when established in the immunized host. The immunotherapeutic effect of herpes vaccines seems less convincing. However, introduction of new adjuvants, which shift the cytokine production of helper T-cells toward stimulation of cytotoxic T-cells (TH1 type cytokine response), reveals a promising development. Mathematical analysis proved that overall prophylactic vaccination of seronegative women, even when eliciting 40-60 % antibody response only, would reduce the frequency of genital herpes within the vaccinated population. Even when partially effective, immunotherapeutic vaccination might represent a suitable alternative of chronic chemotherapy in recurrent labial and genital herpes.

Chapter 21: Modelling the impact of HPV vaccines on cervical cancer and screening programmes

The impact of human papillomavirus (HPV)-16/18 vaccination on the incidence of infection and disease can be explored in a range of different models. Here we explore the epidemiological and economic impact of vaccination where screening is absent and where it is well established. The importance for epidemiology of assumptions about naturally-acquired immunity and heterogeneity in risk behaviours are highlighted, as are the importance for health economic outcomes of vaccine costs and the ability to modify screening strategies. To date, model results are consistent in predicting a useful role for vaccine, but further epidemiological data are required to help test the validity of models.

The Public Health Imperative for a Neonatal Herpes Simplex Virus Infection Surveillance System

About 1 in 5 sexually active adults in the United States has serologic evidence of genital herpes caused by herpes simplex virus type-2. Neonatal herpes simplex virus infection is a serious consequence of genital herpes infection. Herpes infection in neonates causes significant morbidity and neurologic damage and generally has a case-fatality ratio untreated of 60%. It is estimated that 440 to 1,320 cases of neonatal herpes infections occur in the United States per year (11-33 cases occur per 100,000 live births). Given the challenges in surveillance for genital herpes due to the large number of asymptomatic infections and infrequent laboratory-based diagnosis, we recommend that to begin an effective national control program for herpes infections, a mandatory national surveillance system for neonatal herpes be implemented. Such a system would help assure appropriate therapy, help monitor trends and understand the burden of disease, identify risk determinants, and evaluate prevention efforts.

Seroprevalence atlas of infections with oncogenic and non-oncogenic human papillomaviruses in Finland in the 1980s and 1990s

Vaccines against high-risk (hr) human papillomaviruses (HPVs) causing cervical cancer may soon be licensed. Thus, nature of HPV epidemics needs to be studied now. Random sampling for studies on HPV epidemiology was done from all 230,998 women belonging to the population-based Finnish Maternity Cohort and having a minimum of 2 pregnancies between 1983 and 1994. First pregnancy serum specimens were retrieved for 7,805 subjects, and were analyzed for antibodies to HPV6/11, 16 and 18 with standard ELISAs. HPV16 seroprevalence almost doubled from the 1980s to the 1990s, and the epidemic spread to new areas in 23-31 year olds, i.e. the bulk of pregnant female population in the southwest part of the country. The HPV16 epidemic in the 14-22 year olds in 1983-1988 (1961-1974 birth cohorts) and in the 23-31 year olds in 1989-1994 (1958-1971 birth cohorts) overlapped with strong clustering of HPV16 and HPV18 infections in the latter (odds ratio 8.0, 95% confidence interval 6.6-9.7). Similar clustering of HPV16 and HPV6/11 infections was not found. The epidemic and the clustering may be due to high transmission probability of the hrHPV types and increase in sexual activity of the index birth cohorts.

Attitudes about human papillomavirus vaccine among family physicians

STUDY OBJECTIVE

Human papillomavirus (HPV) vaccines will soon be available for clinical use, and the effectiveness of vaccine delivery programs will depend largely upon whether providers recommend the vaccine. The objectives of this study were to examine family physicians' attitudes about HPV immunization and to identify predictors of intention to recommend immunization.

DESIGN

Cross-sectional survey instrument assessing provider and practice characteristics, knowledge about HPV, attitudes about HPV vaccination, and intention to administer two hypothetical HPV vaccines.

PARTICIPANTS

Surveys were mailed to a national random sample of 1,000 American Academy of Family Physicians (AAFP) members.

MAIN OUTCOME MEASURE

Intention to administer two hypothetical HPV vaccines (a cervical cancer/genital wart vaccine and a cervical cancer vaccine) to boys and girls of different ages.

RESULTS

One hundred fifty-five surveys (15.5%) were returned and 145 were used in the final sample. Participants reported higher intention to recommend both hypothetical HPV vaccines to girls vs. boys (P < 0.0001) and to older vs. younger adolescents (P < 0.0001). They were more likely to recommend a cervical cancer/genital wart vaccine than a cervical cancer vaccine to boys and girls (P < 0.001). Variables independently associated with intention (P < 0.05) included: female gender of provider, knowledge about HPV, belief that organizations such as the AAFP would endorse vaccination, and fewer perceived barriers to vaccination.

CONCLUSIONS

Female gender, knowledge about HPV, and attitudes about vaccination were independently associated with family physicians' intention to recommend HPV vaccines. Vaccination initiatives directed toward family physicians should focus on modifiable predictors of intention to vaccinate, such as HPV knowledge and attitudes about vaccination.

Pediatricians' intention to administer human papillomavirus vaccine: the role of practice characteristics, knowledge, and attitudes

PURPOSE

The objective of this study was to examine pediatrician characteristics and attitudes associated with intention to recommend two hypothetical human papillomavirus (HPV) vaccines.

METHODS

A survey instrument mailed to a random sample of 1000 pediatricians assessed provider characteristics, HPV knowledge, and attitudes about HPV vaccination. Intention to administer each of two HPV vaccines types (a cervical cancer/genital wart vaccine and a cervical cancer vaccine) to girls and boys of three different ages (11, 14, and 17 years) was assessed. Linear mixed modeling for repeated measures and multivariable linear regression models were performed to identify variables associated with intention to recommend vaccination.

RESULTS

The mean age of participants (n = 513) was 42 years and 57% were female. Participants were more likely to recommend vaccination to girls vs. boys and older vs. younger children, and were more likely to recommend a cervical cancer/genital wart vaccine than a cervical cancer vaccine (p < .0001). Variables independently associated with intention to recommend a cervical cancer/genital wart vaccine were: higher estimate of the percentage of sexually active adolescents in one's practice (beta .084, p = .002), number of young adolescents seen weekly (beta 1.300, p = .015), higher HPV knowledge (beta 1.079, p = .015), likelihood of following the recommendations of important individuals and organizations regarding immunization (beta .834, p = .001), and fewer perceived barriers to immunization (beta -.203, p = .001).

CONCLUSIONS

Vaccination initiatives directed toward pediatricians that focus on modifiable predictors of intention to vaccinate, such as HPV knowledge and attitudes about vaccination, may facilitate adherence to emerging national immunization guidelines.

Vaccines for sexually transmitted infections

STIs are responsible for significant human suffering and carry significant economic costs. Strategies to control STIs, such as screening programs and condoms, have had limited success. Vaccines offer an additional method that is not coitally related and does not depend on consistent use. The HPV vaccine confers protection against the most common types causing cervical dysplasia. Mathematical modeling suggests that the HSV vaccine, given universally to all young women, should reduce genital and neonatal herpes in the population at large. Much work remains on vaccines for chlamydia and gonorrhea, but they offer the hope of preventing pelvic inflammatory disease and its sequelae. As these vaccines become licensed, their successful implementation will require the support of professional organizations, families, and providers.

Progress in vaccines for sexually transmitted diseases

The development pipeline for vaccines to control sexually transmitted infections holds greater promise than ever before. Preclinical studies are encouraging in the development of chlamydia and gonococcal vaccines, and for the first time, recent clinical trials have shown the feasibility of creating vaccines to control genital herpes and cervical human papillomavirus infections. Behavioral research suggests that these vaccines will likely find acceptance among health care providers and consumers.

Herpes simplex virus in pregnancy: new concepts in prevention and management

Genital herpes simplex virus (HSV) infection is one of the most common viral sexually transmitted diseases in the United States. It is estimated that 45 million adolescents and adults are infected with genital HSV. Most genital herpes infections in the United States are caused by HSV type 2 (HSV-2), and 25% to 30% of women of reproductive age have HSV-2 antibodies. What is more striking is that genital herpes is frequently under-recognized, and that only 5% to 10% of these women have a history of genital herpes. Because such a small percentage of women are aware of being infected with HSV, the risk of maternal transmission of this virus to the fetus or newborn is a significant health issue.

Predictors of STI vaccine acceptability among parents and their adolescent children

PURPOSE

To identify attitudes and behavioral factors associated with parental intent to vaccinate their adolescent children against sexually transmitted infections (STI) and adolescent intent to accept vaccination for the prevention of STI.

METHODS

In this cross-sectional study, 320 parents and their adolescent children (aged 12-17 years) were recruited from urban adolescent health clinics and private practice pediatric offices to complete audio, computer-assisted self-interviews (A-CASI). Parents and their adolescents were asked about acceptability of gonorrhea, genital herpes, and human immumodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) vaccines. These three items were summed to create an STI vaccine acceptability scale, the primary outcome variable. Potential predictors measured included health beliefs, sociodemographic factors, and health and sexual behaviors.

RESULTS

A substantial majority of parents and their adolescent children rated the three STI vaccines as very acceptable. Parental health beliefs and parental history of STI diagnosis were significant independent predictors of intent to vaccinate adolescent children against STI. Parental intent to vaccinate and having a friend who had engaged in sexual intercourse were significant independent predictors of adolescents' intent to accept STI vaccination.

CONCLUSIONS

The majority of these parents and their adolescent children found STI vaccination very acceptable, suggesting that there will be great interest in these vaccines once they become available. Interventions designed to address parental health beliefs may prove successful at maintaining or increasing interest in STI vaccines. Adolescents are likely to look to their parents for guidance around acceptance of these vaccines, but personal experiences also may play a role.

Parents'/guardians' willingness to vaccinate their children against genital herpes

PURPOSE

To describe parents' acceptance of a hypothetical herpes simplex virus type 2 (HSV-2) vaccine, attitudes toward vaccine legislation, beliefs regarding appropriate timing of vaccination and correlates of vaccine acceptance.

METHODS

A telephone survey of 315 parents/guardians in the Southeast United States. Descriptive statistics describe the sample's overall attitudes toward HSV-2 vaccination, vaccine legislation, and age preferences. A logistic regression model tested the correlates of intention to vaccinate their children against HSV-2.

RESULTS

A majority of parents (69%) said they would have their children vaccinated. Nearly one-third (29.3%) thought genital herpes vaccination should take place between the ages of 11 and 13 years. Logistic regression revealed that females, single parents, parents whose children had influenza shots, those with more favorable attitudes to vaccination in general, and those who believed sexually transmitted disease (STD) vaccines would be beneficial were more likely to state they would vaccinate their children.

CONCLUSIONS

Overall, a large proportion of parents indicated they would accept HSV-2 vaccination for their children. These results help identify those parents who may or may not be open to vaccinating their children against HSV-2 and inform future interventions to encourage HSV-2 vaccination. This research highlights the need for interventions that differentially target those who would and would not be likely to support vaccination of their children. Results also indicate that many parents believe vaccination should be given after an age when many adolescents have initiated sexual activity. Interventions to promote STD vaccines should not only encourage vaccination, but should also seek to change parental attitudes about optimal timing of the vaccination.

Role of Herd Immunity in Determining the Effect of Vaccines against Sexually Transmitted Disease

BACKGROUND

Vaccination programs provide both direct protection to those immunized and herd immunity, which is indirect protection of those who remain susceptible, owing to a reduced prevalence of infections.

METHODS

The well-understood impact of vaccination against ubiquitous childhood infections is compared with that of vaccination against sexually transmitted infections (STIs), and theoretical insights are derived from a review of mathematical modeling studies.

RESULTS

Typically, a large fraction of cases of STIs are acquired by those with modest risk, and these cases could be prevented by low-efficacy vaccines. If coverage is good, vaccination of only one sex can protect the other sex. Candidate vaccines against human papillomavirus (HPV) and genital herpes are in the final stages of testing. The former is likely to be highly efficacious for a limited number of disease-causing HPV types, and the latter has provided protection against disease in women who initially were seronegative for both herpes simplex virus (HSV) type 1 and HSV-2, with 73% efficacy. In models, this vaccine had a substantial impact when infectiousness was assumed to be reduced along with incidence of disease.

CONCLUSION

With such vaccines on the horizon, the requirements for vaccine delivery need to be considered, particularly who should be vaccinated and at what age.

Pediatrics and herpes simplex virus vaccines

This review explores the development of prophylactic genital herpes vaccines and their potential impact on perinatal and oral-facial disease. Vaccine strategies have included the use of whole killed virus, viral subunits, attenuated live virus, viral vectors, and bare DNA. To date, the recombinant subunit vaccine, truncated HSV-2 gD and alum/MPL, has been the most efficacious. The vaccine is 73 to 74 percent effective in preventing genital disease in herpes simplex virus seronegative women but is not effective in men or seropositive women. Models predict a significant impact on genital herpes if it limits viral shedding. Reductions in perinatal and oral-facial disease are likely to occur as well. Once an efficacious herpes vaccine is available, its effectiveness will depend ultimately on vaccine acceptance by professional organizations, healthcare professionals, and parents. Further research is required to improve on and fully understand the implications of prophylactic herpes simplex vaccines.