Vaccination Of Susceptible Individuals Research Articles

A mathematical analysis of the effects of control strategies on the transmission dynamics of Chlamydiosis

Chlamydiosis remains a major public health concern in both developed and developing countries due to its effects on the human reproductive system. While limited modeling studies have been conducted on the transmission dynamics of the disease, none of them have examined the impacts of the combination of environmental hygiene and other control strategies. In this paper, we present a mathematical model to investigate the impacts of public health education, vaccination of susceptible individuals, treatment of symptomatic infected individuals, and environmental hygiene. The basic reproduction number is computed using the next-generation operator and is employed in the stability analysis of equilibrium points. We also perform a sensitivity analysis of the model using a normalized forward sensitivity index to identify the parameters significantly affecting the effective reproduction number. Findings from analytical solutions and numerical simulations demonstrate that, public health education, vaccination, treatment, and environmental hygiene significantly reduce chlamydiosis incidence and prevalence in the population. Consequently, the study recommends implementing these control measures, particularly in regions where the disease is endemic. Thus, findings from this study could be utilized to support decision-making in Chlamydiosis control strategies.

Transmission of COVID-19 in the presence of single-dose and double-dose vaccines with hesitancy: mathematical modeling and optimal control analysis

IntroductionThe unexpected emergence of novel coronavirus identified as SAR-CoV-2 virus (severe acute respiratory syndrome corona virus 2) disrupted the world order to an extent that the human activities that are core to survival came almost to a halt. The COVID-19 pandemic created an insurmountable global health crisis that led to a united front among all nations to research on effective pharmaceutical measures that could stop COVID-19 proliferation. Consequently, different types of vaccines were discovered (single-dose and double-dose vaccines). However, the speed at which these vaccines were developed and approved to be administered created other challenges (vaccine skepticism and hesitancy).MethodThis paper therefore tracks the transmission dynamics of COVID-19 using a non-linear deterministic system that accounts for the unwillingness of both susceptible and partially vaccinated individuals to receive either single-dose or double-dose vaccines (vaccine hesitancy). Further the model is extended to incorporate three time-dependent non-pharmaceutical and pharmaceutical intervention controls, namely preventive control, control associated with screening-management of both truly asymptomatic and symptomatic infectious individuals and control associated with vaccination of susceptible individuals with a single dose vaccine. The Pontryagin's Maximum Principle is applied to establish the optimality conditions associated with the optimal controls.ResultsIf COVID-19 vaccines administered are imperfect and transient then there exist a parameter space where backward bifurcation occurs. Time profile projections depict that in a setting where vaccine hesitancy is present, administering single dose vaccines leads to a significant reduction of COVID-19 prevalence than when double dose vaccines are administered. Comparison of the impact of vaccine hesitancy against either single dose or double dose on COVID-19 prevalence reveals that vaccine hesitancy against single dose is more detrimental than vaccine hesitancy against a double dose vaccine. Optimal analysis results reveal that non-pharmaceutical time-dependent control significantly flattens the COVID-19 epidemic curve when compared with pharmaceutical controls. Cost-effectiveness assessment suggest that non-pharmaceutical control is the most cost-effective COVID-19 mitigation strategy that should be implemented in a setting where resources are limited.DiscussionPolicy makers and medical practitioners should assess the level of COVID-19 vaccine hesitancy inorder to decide on the type of vaccine (single-dose or double-dose) to administer to the population.

Serological Evaluation for Measles among Italian and Foreign Medical Students in a University Hospital in Rome.

Measles infection in the hospital setting is a major issue. Despite the availability of an effective vaccine, measles outbreaks continue to occur in some European countries. We aimed to evaluate the immunological status of medical students attending the Tor Vergata Polyclinic (PTV). Measles antibodies titers were assessed by venipuncture on a sample of 2717 medical students who underwent annual health surveillance visits from January 2021 to March 2023. Subjects showing serum IgG values above 1.0 S/CO were considered serologically protected. Personal data, country of origin, and main demographic characteristic were also collected. 66.7% (1467 Italian and 346 foreign) of medical students showed protective IgG antibodies levels. Female students were serologically immune more frequently than males (68.6% vs. 63.3%; p < 0.01 at Chi2). The mean antibody titer was 1.72 S/CO, significantly higher in females than males (1.67 vs. 1.75, respectively; p < 0.05), and significantly related to age (p < 0.01). Albanian students, who were the largest foreign population in our study, showed a low serological protection rate (40/90: 44.4%). The proportion of serologically non-immune students is high, raising concerns about the possible risk of hospital transmission. Substantial differences in the rate of immunity have been found between subjects coming from different parts of Europe and the world. Pre-training assessment of all medical students and vaccination of susceptible individuals is highly recommended, particularly for those from low immunization rate countries.

Hand, Foot, and Mouth Disease: A Narrative Review.

Hand, foot, and mouth disease is a common viral disease in childhood. Because the disease has the potential to reach epidemic levels and mortality is high in some countries, early recognition of this disease is of paramount importance. This purpose of this article is to familiarize pediatricians with the clinical manifestations and management of hand, foot, and mouth disease. A search was conducted in February 2022 in PubMed Clinical Queries using the key term "hand, foot, and mouth disease". The search strategy included all clinical trials, observational studies, and reviews published within the past 10 years. Only papers published in English were included in this review. Hand, foot, and mouth disease is characterized by a painful oral enanthem and asymptomatic exanthem on the palms and soles. Children younger than 5 years are most commonly affected. Hand, foot, and mouth disease caused by enterovirus A71 is more severe and has a higher rate of complications than that attributed to other viruses such as coxsackievirus A16. Circulatory failure secondary to myocardial impairment and neurogenic pulmonary edema secondary to brainstem damage are the main causes of death. Fortunately, the disease is usually benign and resolves in 7 to10 days without sequelae. Given the self-limited nature of most cases, treatment is mainly symptomatic and supportive. Intravenous immunoglobulin should be considered for the treatment of severe/complicated hand, foot, and mouth disease and has been recommended by several national and international guideline committees. Currently, there are no specific antiviral agents approved for the treatment of the disease. Drugs such as ribavirin, suramin, mulberroside C, aminothiazole analogs, and sertraline have emerged as potential candidates for the treatment of hand, foot, and mouth disease. Vaccination of susceptible individuals in high-risk areas and good personal hygiene are important preventative measures to combat the disease. Familiarity of the disease including its atypical manifestations is crucial so that a correct diagnosis can be made, and appropriate treatment initiated. A timely diagnosis can help avoid contact with the affected individual and decrease the risk of an outbreak.

A mechanistic model for airborne and direct human-to-human transmission of COVID-19: effect of mitigation strategies and immigration of infectious persons.

The COVID-19 pandemic is the most significant global crisis since World War II that affected almost all the countries of our planet. To control the COVID-19 pandemic outbreak, it is necessary to understand how the virus is transmitted to a susceptible individual and eventually spread in the community. The primary transmission pathway of COVID-19 is human-to-human transmission through infectious droplets. However, a recent study by Greenhalgh et al. (Lancet 397:1603–1605, 2021) demonstrates 10 scientific reasons behind the airborne transmission of SARS-COV-2. In the present study, we introduce a novel mathematical model of COVID-19 that considers the transmission of free viruses in the air beside the transmission of direct contact with an infected person. The basic reproduction number of the epidemic model is calculated using the next-generation operator method and observed that it depends on both the transmission rate of direct contact and free virus contact. The local and global stability of disease-free equilibrium (DFE) is well established. Analytically it is found that there is a forward bifurcation between the DFE and an endemic equilibrium using central manifold theory. Next, we used the nonlinear least-squares technique to identify the best-fitted parameter values in the model from the observed COVID-19 mortality data of two major districts of India. Using estimated parameters for Bangalore urban and Chennai, different control scenarios for mitigation of the disease are investigated. Results indicate that the vaccination of susceptible individuals and treatment of hospitalized patients are very crucial to curtailing the disease in the two locations. It is also found that when a vaccine crisis is there, the public health authorities should prefer to vaccinate the susceptible people compared to the recovered persons who are now healthy. Along with face mask use, treatment of hospitalized patients, and vaccination of susceptibles, immigration should be allowed in a supervised manner so that economy of the overall society remains healthy.

An SIRS Epidemic Model Supervised by a Control System for Vaccination and Treatment Actions Which Involve First-Order Dynamics and Vaccination of Newborns

This paper analyses an SIRS epidemic model with the vaccination of susceptible individuals and treatment of infectious ones. Both actions are governed by a designed control system whose inputs are the subpopulations of the epidemic model. In addition, the vaccination of a proportion of newborns is considered. The control reproduction number Rc of the controlled epidemic model is calculated, and its influence in the existence and stability of equilibrium points is studied. If such a number is smaller than a threshold value R¯c, then the model has a unique equilibrium point: the so-called disease-free equilibrium point at which there are not infectious individuals. Furthermore, such an equilibrium point is locally and globally asymptotically stable. On the contrary, if Rc&gt;R¯c, then the model has two equilibrium points: the referred disease-free one, which is unstable, and an endemic one at which there are infectious individuals. The proposed control strategy provides several free-design parameters that influence both values Rc and R¯c. Then, such parameters can be appropriately adjusted for guaranteeing the non-existence of the endemic equilibrium point and, in this way, eradicating the persistence of the infectious disease.

Factors associated with adults\u2019 actions to confirm their own rubella immune status in Japan\u2019s drive toward rubella elimination: Cross-sectional online survey of non-healthcare workers in their 20s to 40s

BackgroundRubella outbreaks occurred among adults in Japan in 2013-2014 and 2018-2019 due to immunity gaps. In response and aiming at rubella elimination by 2020, the government introduced countermeasures comprising supplementary immunization activities for voluntary testing of adult non-healthcare-related workers and vaccination of susceptible individuals. However, as of October 2020, rubella immunity testing and vaccination rates remained low. This study was conducted to identify factors associated with adults voluntarily confirming their rubella immune status, to help develop effective promotion activities for hard-to-reach and left-behind populations.MethodsIn this cross-sectional study, a general population sample of non-healthcare workers aged 20-49 years in Japan completed an online survey in November 2020. Univariate analysis was performed to examine associations of specific actions taken to confirm rubella immune status with social background characteristics, knowledge of rubella, and attitude to testing and vaccination. Log binomial regression analysis was performed to explore the associations following adjustment for social background characteristics.ResultsAmong 1,854 respondents (927 men, 927 women), only 23.4% of men and 39.4% of women in their 20s to 40s have taken some action related to rubella prevention. Three major factors were associated with the targeted population having taken voluntary action: (1) knowing about testing for confirmation of immunity status (adjusted odds ratio [AOR] 4.29 men, 2.89 women), the rubella outbreak in 2013 among men in their 20s to 40s (AOR 2.79 men, 1.64 women), and congenital rubella syndrome (AOR 1.89 men, 3.10 women); (2) having acquaintances who were vaccinated against or tested for rubella (AOR 2.98 men, 1.95 women); and (3) having a positive attitude toward influenza vaccination (AOR 2.48 men, 1.83 women). Marriage, desire for pregnancy, and having children were weakly associated with taking action.ConclusionsCurrently, insufficient voluntary action is being taken by high-risk adult populations to close the identified immunity gaps. In this last mile to rubella elimination, our findings and suggested potential interventions via annual health check-ups and occupational health and public health initiatives could prove helpful in developing further countermeasures that actively promote and implement supplementary immunization activities targeting all adult generations.

MATHEMATICAL MODELLING AND ANALYSIS OF CHOLERA DISEASE DYNAMICS WITH CONTROL

A deterministic mathematical model of cholera infection incorporating health education campaign, vaccination of susceptible humans, treatment of infected human and water sanitation is developed. It is shown that the solution of the model uniquely exist, it is positive and bounded in a certain region. The disease-free equilibrium (DFE) state of the model was determined and used to compute the basic reproduction number as a threshold for effective disease management. The result from stability analysis for the disease-free equilibrium state (DFEs) shows that it is locally as well as globally asymptotically stable whenever the basic reproduction number is less than unity (). The results obtained from the sensitivity index of show that the control parameters of public health education campaign, vaccination of susceptible individuals, treatment of infected humans and water sanitation are crucial parameters to cholera management. Numerical simulations show that, expanded and improved vaccination among other interventions is crucial in decreasing cholera burden. Furthermore, from the numerical simulations and results it is recommended that a combination of mass and consistent public health education campaigns, expanded vaccination coverage, prompt treatment of infected individuals, with water sanitation, is vital to public health strategies in eradicating cholera infection and deaths in the shortest possible time

Cost-effectiveness analysis of a cholera model with awareness programs and limited resources

In this paper, we developed a mathematical model to describe the dynamics of Cholera with awareness programs under limited resources. The model was fully analysed and the threshold for the eradication of the disease was given. It was proven that the model undergoes a backward bifurcation under certain conditions. The model is then extended to include optimal controls, namely: vaccination of susceptible individuals, killing of vectors, and water sanitation. Numerical simulations for the application of a single control, combinations of two controls and all three controls were given. Cost-effectiveness analysis was carried out in order to determine the most cost-effective control strategies, which was found to be the combination of vaccination and water sanitation.

Cost-effectiveness analysis of a cholera model with awareness programs and limited resources

In this paper, we developed a mathematical model to describe the dynamics of Cholera with awareness programs under limited resources. The model was fully analysed and the threshold for the eradication of the disease was given. It was proven that the model undergoes a backward bifurcation under certain conditions. The model is then extended to include optimal controls, namely: vaccination of susceptible individuals, killing of vectors, and water sanitation. Numerical simulations for the application of a single control, combinations of two controls and all three controls were given. Cost-effectiveness analysis was carried out in order to determine the most cost-effective control strategies, which was found to be the combination of vaccination and water sanitation.

Deterministic Epidemic Models for Ebola Infection with Time-Dependent Controls

In this paper, we have studied epidemiological models for Ebola infection using nonlinear ordinary differential equations and optimal control theory. We considered optimal control analysis of SIR and SEIR models for the deadly Ebola infection using vaccination, treatment, and educational campaign as time-dependent control functions. We have applied indirect methods to study existing deterministic optimal control epidemic models for Ebola virus disease. These methods in optimal control are based on Hamiltonian function and Pontryagin’s maximum principle to construct adjoint equations and optimality systems. The forward-backward sweep numerical scheme with the fourth-order Runge–Kutta method is used to solve the optimality system for the various control strategies. From our numerical illustrations, we can conclude that effective educational campaigns and vaccination of susceptible individuals as well as effective treatments of infected individuals can help reduce the disease transmission.

An investigation of a measles outbreak in Japan and China, Taiwan, China, March-May 2018.

ObjectiveTo investigate a measles outbreak that spread to Japan and China, Taiwan, China during March–May 2018, exploring the characteristics of the super-spreading event.MethodsA contact investigation of the index case and reconstruction of the epidemiological dynamics of measles transmission were conducted. Employing a mathematical model, the effective reproduction number was estimated for each generation of cases.Results and discussionA single index case gave rise to a total of 38 secondary cases, 33 in Japan and five in China, Taiwan, China. Subsequent chains of transmission were observed in highly vaccinated populations in both Japan and China, Taiwan, China. The effective reproduction number of the second generation was > 1 for both Japan and China, Taiwan, China. In Japan, the reproduction number was estimated to be < 1 during the third generation. Vaccination of susceptible individuals is essential to prevent secondary and tertiary transmission events.

Intervention-Based Stochastic Disease Eradication

Disease control is of paramount importance in public health, with infectious disease extinction as the ultimate goal. Although diseases may go extinct due to random loss of effective contacts where the infection is transmitted to new susceptible individuals, the time to extinction in the absence of control may be prohibitively long. Intervention controls are typically defined on a deterministic schedule. In reality, however, such policies are administered as a random process, while still possessing a mean period. Here, we consider the effect of randomly distributed intervention as disease control on large finite populations. We show explicitly how intervention control, based on mean period and treatment fraction, modulates the average extinction times as a function of population size and rate of infection spread. In particular, our results show an exponential improvement in extinction times even though the controls are implemented using a random Poisson distribution. Finally, we discover those parameter regimes where random treatment yields an exponential improvement in extinction times over the application of strictly periodic intervention. The implication of our results is discussed in light of the availability of limited resources for control.

Brote de varicela en un centro ocupacional para adultos con disminución psíquica

An outbreak of varicella is described in a training and work center for psychologically handicapped adults with a high susceptibility to the disease. Descriptive and case-control study. A questionnaire self-complimented by parents and staff of the center was used. A serologic study in order to determine antibodies againts varicella was carried out for people without varicella vaccination or disease history. Four cases of varicella occurred among 56 students of the center and none among the staff (12 people). 51.8% of students had not history of varicella versus 8.3% of staff (p = 0.009). A recommendation of vaccination against varicella was made for people without history of varicella, and 52.2% were vaccinated. After vaccination, no new cases occurred. In the serological study (11 students and 1 staff), 5 students were sero-negative. In the case-control study, risk of suffering varicella was lower for students with history of varicella, those vaccinated against varicella and those attending less commonly the center. The outbreak occurred in a high susceptible population, and it is suggested that it is a previously unidentified group of risk. Serological studies of varicella with vaccination of susceptible individuals in these populations may be indicated.

Critical prevalence of antibodies minimizing vaccination costs for hepatitis A, hepatitis B, varicella, measles and tetanus in adults and adolescents in Catalonia, Spain

The prevalence of seropositive individuals that makes costs of vaccinating all individuals equal to that for screening and vaccination of susceptible individuals is defined as the critical prevalence of antibodies ( p ∗). Screening and vaccination is more efficient when the prevalence of seropositive individuals ( p) in the population is higher than p ∗. In this study, the formula to obtain p ∗ was derived from the cost-effectiveness equations, showing that it depends on screening and vaccination costs, programme compliance, screening test performance, vaccine efficacy and disease costs. The formula was used to determine the least costly vaccination strategy for hepatitis A and B, varicella, measles and tetanus in adults and adolescents in Catalonia. The least costly vaccination strategy was vaccination without screening (since p was lower than p ∗) for hepatitis B, measles and tetanus in adults and adolescents (5–14 years) and for hepatitis A in individuals aged 5–24 years, and screening and vaccination (since p was higher than p ∗) for varicella in adults and adolescents and for hepatitis A in adults aged >24 years. Vaccination strategies based on the critical prevalence of antibodies could maximize the immunity level in the community from available resources.

Smallpox: Implications for Infection Control Practitioners — Part Two

In this, the second of a two-part article, the implications of smallpox for infection control practitioners are examined. Since the events in New York on 11 September 2001, there has been renewed speculation about terrorists' abilities to initiate biological warfare using highly infectious diseases such as smallpox. There is no effective cure for smallpox and current infection control strategies rely heavily on heightened surveillance, isolation techniques and vaccination of susceptible individuals. Much of the world's population has neither been exposed to the smallpox virus nor vaccinated against it, and so is vulnerable to infection. Furthermore, many healthcare staff have no experience with diagnosis, management or prevention of smallpox and there is a risk that the disease may spread rapidly if it is not recognised quickly. Smallpox begins with non-specific symptoms that can occur with many viral illnesses; misdiagnosis and delayed diagnosis is a very real risk, even in the presence of a rash. This situation has fuelled debate that pre-emptive mass vaccination against smallpox should be introduced to protect the population from the threat of a deliberate release of smallpox.

Varicella zoster virus immunity in multinational health care workers of a Saudi Arabian hospital

Introduction The health care worker (HCW) is vulnerable to hospital-acquired varicella zoster virus (VZV) infection, and thereafter may transmit infection to coworkers and patients who are susceptible and hospitalized. Interventions to prevent varicella transmission in HCW groups of uncertain immunity prove labor intensive, costly, and disruptive. Therefore, documentation of total varicella immunity in HCWs is desirable. Setting The National Guard King Abdulaziz Medical City is a 600-bed tertiary care center in Riyadh, Saudi Arabia with a multinational staff. Material and method A program to assess the VZV status of HCWs was initiated in 1999. The survey was confined to HCWs having direct patient contact. Questions elucidated previous history of varicella (chicken pox) infection, antibody testing against varicella, and varicella vaccination. HCWs with a negative or unknown history were subsequently tested for varicella antibodies (IgG). Results Seventy-six percent (2047) of the HCWs responded to the questionnaire. Of these, 562 (28%) were physicians, 761 (37%) were nurses, 438 (21%) were medical technicians, and 286 (14%) were involved in clerical work. A total of 802 (39%) were from the Middle East including Saudi Arabia, 633 (31%) were from the Far East, 361 (18%) were from the West and from temperate areas, 138 (7%) were from South Africa, and 113 (5%) were from other nationalities. A previous history of VZV infection was reported by 1303 (64%); 262 (13%) had a history of positive test for varicella antibody, and only 44 (2%) had a history of varicella vaccination. Of the 744 (36%) HCWs who had a negative or unknown history of VZV infection, 217 (29%) underwent antibody testing. Of these, 181 (83%) proved to be immune (IgG ≥ 1.10), and 36 (17%) nonimmune (IgG < 1.2). The latter group have completed varicella immunization. Staff from the West (81%), Far East (78%), and South Africa (59%) reported more histories of VZV infection compared with the employees of Middle Eastern origin (46%) (P < .001) and disclosed a history of positive antibodies in 13%, 18%, 17%, and 8%, respectively (P < .001). In relation to occupation, nurses reported history of varicella infection (75%) and a history of positive varicella antibodies (16%) more than physicians (54% and 8%, respectively) (P < .05). Conversely, serologic immunity to VZV infection proved consistent among the different nationalities and among the 4 occupational groups. Conclusion Total varicella immunity of a multinational workforce can be realized through screening of HCWs and vaccination of susceptible individuals. It is preferred above repeated interventions after varicella exposure for its simplicity, cost-effectiveness, and efficiency. Knowledge of VZV infection varies between different nationalities and cannot be used as a true predictor of immunity. There is no difference in the immunity by antibody testing of staff recruited from temperate and tropical climates. Total varicella immunity should, therefore, be achieved through screening of all HCWs and vaccination of those susceptible.

Smallpox: implications for infection control practitioners. Part one: disease characteristics and history

In this, the first of a two-part article, the history and characteristics of smallpox disease are examined, together with a discussion of vaccination strategies. Since the events in New York on 11 September 2001, there has been renewed speculation about terrorists' abilities to initiate biological warfare using highly infectious diseases such as smallpox. There is no effective cure for smallpox and current infection control strategies rely heavily on heightened surveillance, isolation techniques and vaccination of susceptible individuals. Much of the world's population has neither been exposed to the smallpox virus nor vaccinated against it, and so is vulnerable to infection. Furthermore, many healthcare staff have no experience with diagnosis, management or prevention of smallpox and there is a risk that the disease may rapidly spread if it is not recognised quickly. Smallpox begins with non-specific symptoms that can occur with many viral illnesses; misdiagnosis and delayed diagnosis is a very real risk, even in the presence of a rash. This situation has fuelled debate that pre-emptive mass vaccination against smallpox should be introduced to protect the population from the threat of a deliberate release of smallpox.

The Cost-Effectiveness of Varicella Screening and Vaccination in U.S. Army Recruits

Varicella outbreaks in the U.S. Army disrupt training, reduce readiness, and represent substantial costs. Vaccination of susceptible individuals may be cost-effective. We conducted a cost-effectiveness analysis comparing screening of all incoming recruits and vaccination of susceptible individuals at either initial entry training (IET) or medical entrance processing station (MEPS), universal vaccination at IET, and no intervention. Primary health outcomes included the number of varicella cases prevented during the 8-week initial training period. The varicella hospitalization rate was 21.6 per 10,000 per year. In 100,000 recruits, 36 cases of varicella are expected at a cost of $181,000 in the absence of an intervention. Screening at IET would prevent 4 cases but would cost an additional $3,255,000 more than no intervention. Screening at MEPS would prevent 3 cases and save $521,000 per case prevented during the IET but would cost $2,734,000 more than no intervention. Universal vaccination would prevent 2 cases but would cost $15,858,000 more than MEPS screening and $18,592,000 more than no intervention. These results are robust. Cost per case of varicella prevented ranged from $390,000 to $7.9 million. Scarce prevention resources could be more cost-effectively allocated to other prevention programs.

Recombinant vaccinia viruses and gene gun vectors expressing the large subunit of Schistosoma mansoni calpain used in a murine immunization-challenge model

Schistosomiasis is a parasitic disease affecting over 200 million people every year in tropical regions of the world. Drug treatment and other existing control measures are costly and have failed to eliminate the incidence of infection, morbidity and mortality due to Schistosoma mansoni infection. Vaccination of susceptible individuals using recombinant vaccines encoding key S. mansoni antigens may be the most effective and least expensive means of controlling schistosomiasis. A candidate vaccine antigen is p80, the large subunit of the S. mansoni protease, calpain. In our vaccine studies, we have employed both the wild-type p80 and a mutant p80 (mut p80) in which an active site amino acid was genetically altered to create a less proteolytically-active enzyme. Two vaccine delivery approaches were implemented using p80 or mut p80 as vaccine antigen: recombinant vaccinia virus (RVV) inoculation and DNA immunization via the Accell® gene gun (GG) delivery system. RVV's expressing p80 and mut p80 were generated and tested for recombinant protein expression in vitro. These RVV's were tested for protective capacity in mouse challenge studies. Neither subcutaneous nor intranasal vaccinations with RVV-p80 or RVV-mut p80 were capable of significantly reducing the mean worm burdens of vaccinated mice. A GG-RVV combination immunization regime using WRG-vectors encoding p80 and mut p80 for GG priming and the RVV's for boosting prior to S. mansoni challenge infection was performed and no significant protection was obtained over two repeated studies. However, duplicate challenge studies involving GG immunization of mice with WRG-vectors encoding p80 or mut p80 revealed that 3 inoculations of mice with WRG-full5′ mut p80 (containing the full 5′ untranslated region of mut p80) provided 60% protection which was statistically significant ( p<0.05). These preliminary in vivo studies demonstrate the potential for further study of the protection afforded by gene gun-delivered WRG-full5′ mut p80 into subsequently-challenged mice. Such studies may pave the way to effective vaccination of humans using WRG DNA vectors expressing a schistosomal calcium-activated neutral protease.