Road transect surveys do not reveal any consistent effects of a toxic invasive species on tropical reptiles

Effects of perturbations to wildlife often are measured by changes in rates of encounter with animals during standardised surveys, such as along roads. Previous work has predicted that the invasion of toxic cane toads (Rhinella marina) through the Australian tropics will cause massive mortality of anuran-eating snakes, and influence abundances of other native species. We surveyed three adjacent road transects for nocturnal snakes and lizards, beginning shortly before toads arrived at this site near Darwin, in the Northern Territory. In the wet-seasons of four successive years, we conducted surveys on 591 nights; on 302 of these nights, all three transects were surveyed. We recorded 8,880 live cane toads and 3,365 live reptiles. Toad numbers increased over time on all three transects but encounters with 13 species of native reptiles varied inconsistently. Eight of the 13 species of native reptile showed no significant change in encounter rates following the arrival of toads. Of the five species that did change in encounter rates, only one taxon (the bluetongue skink, Tiliqua scincoides intermedia) declined across all three transects. Encounter rates of the other four species often increased on at least one transect but decreased on at least one other. Thus, either the impact of cane toads on counts of reptiles differed between nearby sites, or (more likely) other factors had more influence on reptile numbers. A consistent decrease in reptile numbers on the busiest road over the study period suggests that local snake populations were affected more by road-kill than by invasive toads. Without spatial replication, this decrease could have been interpreted as an impact of toad invasion.     

Five-year study of surgical rates in Ontario's counties.

The surgical rates for eight operations (hysterectomy, tonsillectomy/adenoidectomy, cholecystectomy, prostatectomy, appendectomy, mastectomy, colectomy and cesarean section) done in Ontario''s 44 counties from 1973 to 1977 were examined. There was considerable variation among the counties for all the operations studied, although the degree of intercounty variation decreased over the 5 years. Differences in resources (hospital beds and surgeons) explained little of the variation in the rates, but this may be because people crossed county lines for certain operations. Although some counties had consistently high or low rates for individual operations during the 5-year period, only four had consistently high rates for four or more operations, and only five had consistently low rates for four or more. The five counties with teaching health science centres had the highest ratios of specialists and surgeons to population, and, with the exception of one county in 1973, had above-average numbers of hospital beds. Despite the greater resources in these counties, their residents had consistently low rates for cholecystectomy, appendectomy, mastectomy and tonsillectomy/adenoidectomy. However, three of these counties had the highest rates for cesarean section. The variation in the rates is likely due to lack of agreement about indications for surgery or to variation in the use of technology rather than to differences in the incidence or prevalence of disorders.     

Protection of mumps in children with various underlying diseases: application of a live attenuated mumps and trivalent measles-rubella-mumps (MRM) vaccines in these children

A live attenuated mumps and trivalent measles-rubella-mumps (MRM) vaccines have been applied to 887 and 148 children with various underlying diseases at the vaccine clinic of Osaka University Hospital between 1975 and 1985, respectively. Clinical reactions after mumps vaccination occurred in only 7 children (0.8%) and those after MRM vaccination in 28 children (19%), but their underlying diseases were not deteriorated by either vaccination. Clinical follow up study revealed that 2 of the 430 children immunized with mumps vaccine had contracted the disease during 7 year period and 2 of the 123 children immunized with MRM vaccine had contracted clinical mumps or rubella during 3 year period. The seroconversion rates after mumps vaccination were 70% and 61% by the hemagglutination inhibition (HI) test and neutralization (NT) test, respectively, while 94% by the fluorescent antibody to membrane antigen (FAMA) test. Those after MRM vaccination were 87% for measles, 96% for rubella by the HI test and 89% for mumps by the FAMA test. Serological follow up study revealed that antibodies elicited by mumps vaccination were sustained without substantial decline for at least 7 years. These results suggest that a live attenuated mumps and MRM vaccines are safe and effective in children with various underlying diseases.     

Pathogenic simian/human immunodeficiency virus SHIV(KU) inoculated into immunized macaques caused infection, but virus burdens progressively declined with time

Using the simian immunodeficiency virus/human immunodeficiency virus (SHIV)-macaque model of AIDS, we had shown in a previous report that a live, nonpathogenic strain of SHIV, further attenuated by deletion of the vpu gene and inoculated orally into adult macaques, had effectively prevented AIDS following vaginal inoculation with pathogenic SHIV(KU). Examination of lymph nodes from the animals at 18 weeks postchallenge had shown that all six animals were persistently infected with challenge virus. We report here on a 2-year follow-up study on the nature of the persistent infections in these animals. DNA of the vaccine virus was present in the lymph nodes at all time points tested, as far as 135 weeks postchallenge. In contrast, the DNA of SHIV(KU) became undetectable in one animal by week 55 and in three others by week 63. These four macaques have remained negative for SHIV(KU) DNA as far as the last time point examined at week 135. Quantification of the total viral DNA concentration in lymph nodes during the observation period showed a steady decline. All animals developed neutralizing antibody and cytotoxic-T-lymphocyte responses to SHIV(KU) that persisted throughout the observation period. Vaccine-like viruses were isolated from two animals, and a SHIV(KU)-like virus was isolated from one of the two macaques that remained positive for SHIV(KU) DNA. There was no evidence of recombination between the vaccine and the challenge viruses. Thus, immunization with the live vaccine not only prevented disease but also contributed to the steady decline in the virus burdens in the animals.     

Reproductive performance of farmed red deer (Cervus elaphus) in New Zealand. I. Descriptive data.

A longitudinal observational study of 15 red deer (Cervus elaphus) farms was carried out in New Zealand for 2 years from Mar 1992. Management of hind mobs and their composition during mating, calving, and weaning were recorded. About 2700 hinds were individually monitored for live weight, body condition score and reproductive success. All hinds were pregnancy tested in June by ultrasound and classified as having conceived before May 1, after May 1, or as being not pregnant. Calving dates and dam-offspring pairs were recorded on four farms. The lactational status of hinds and live weight of calves were recorded at weaning. Mean pre-mating live weights of yearling hinds were 81.3-82.8 kg and of adult hinds 98.0-98.7 kg, respectively, for each year of study. The percentage of yearling and adult hinds conceiving before May ranged from 8.3 to 95.0% and from 77.6 to 98.4%, respectively, between farms. Overall, the proportion of yearling and adult hinds not pregnant was 15.3% and 3.2%, respectively. Pregnancy rates at scanning of adult hinds within mating mobs were generally over 90%, and 41.7% of mating mobs had 100% pregnancy rates. In contrast, the pregnancy rates of yearling hind mobs were more variable, with five mobs below 50%, and 34.1% of mating mobs achieving 100% pregnancy rate. Estimated in utero loss rates from pregnancy diagnosis to calving were 0.66 and 0.79% for yearling and adult hinds, respectively. From four farms, median calving dates of yearling and adult hinds were Dec 13 and Nov 30, respectively. Overall, calf survival rates to weaning of yearling and adult offspring were 84.1 and 91.6%, respectively, while the reproductive efficiencies (number of calves weaned per hind mated) were 70 and 83.6%, respectively. Farm mean weaner live weights standardised on Apr 1 ranged from 42-59 kg and 39-51 kg for stags and hinds, respectively. These data are currently the best estimates of reproductive parameters of New Zealand red deer herds, and highlight a wide variability in reproductive indices between farms.     

Effectiveness of non-adjuvanted pandemic influenza A vaccines for preventing pandemic influenza acute respiratory illness visits in 4 U.S. communities

We estimated the effectiveness of four monovalent pandemic influenza A (H1N1) vaccines (three unadjuvanted inactivated, one live attenuated) available in the U.S. during the pandemic. Patients with acute respiratory illness presenting to inpatient and outpatient facilities affiliated with four collaborating institutions were prospectively recruited, consented, and tested for influenza. Analyses were restricted to October 2009 through April 2010, when pandemic vaccine was available. Patients testing positive for pandemic influenza by real-time RT-PCR were cases; those testing negative were controls. Vaccine effectiveness was estimated in logistic regression models adjusted for study community, patient age, timing of illness, insurance status, enrollment site, and presence of high-risk medical conditions. Pandemic virus was detected in 1,011 (15%) of 6,757 enrolled patients. Fifteen (1%) of 1,011 influenza positive cases and 1,042 (18%) of 5,746 test-negative controls had record-verified pandemic vaccination >14 days prior to illness onset. Adjusted effectiveness (95% confidence interval) for pandemic vaccines combined was 56% (23%, 75%). Adjusted effectiveness for inactivated vaccines alone (79% of total) was 62% (25%, 81%) overall and 32% (-92%, 76%), 89% (15%, 99%), and -6% (-231%, 66%) in those aged 0.5 to 9, 10 to 49, and 50+ years, respectively. Effectiveness for the live attenuated vaccine in those aged 2 to 49 years was only demonstrated if vaccination >7 rather than >14 days prior to illness onset was considered (61%∶ 12%, 82%). Inactivated non-adjuvanted pandemic vaccines offered significant protection against confirmed pandemic influenza-associated medical care visits in young adults.     

Declining prevalence of hepatitis A virus antibodies among children from low socioeconomic groups reinforces the need for the implementation of hepatitis A vaccination in Brazil

Age-related seroprevalence studies that have been conducted in Brazil have indicated a transition from a high to a medium endemicity of hepatitis A virus (HAV) infection in the population. However, most of these studies have focused on urban populations that experience lower incidence rates of HAV infection. In the current study, the prevalence of anti-HAV antibodies was investigated in children with a low socioeconomic status (SES) that live on the periphery of three capital cities in Brazil. A total of 1,162 dried blood spot samples were collected from individuals whose ages ranged from one-18 years and tested for anti-HAV antibodies. A large number of children under five years old (74.1-90%) were identified to be susceptible to HAV infection. The anti-HAV antibody prevalence reached ≥ 50% among those that were 10-14 years of age or older. The anti-HAV prevalence rates observed were characteristics of regions with intermediate level of hepatitis A endemicity. These data indicated that a large proportion of children with a low SES that live at the periphery of urban cities might be at risk of contracting an HAV infection. The hepatitis A vaccine that is currently offered in Brazil is only available for high-risk groups or at private clinics and is unaffordable for individuals with a lower SES. The results from this study suggest that the hepatitis A vaccine should be included in the Brazilian National Program for Immunisation.     

Sero-Molecular Epidemiology of Japanese Encephalitis in Zhejiang,an Eastern Province of China

BackgroundSporadic Japanese encephalitis (JE) cases still have been reported in Zhejiang Province in recent years, and concerns about vaccine cross-protection and population-level immunity have been raised off and on within the public health sphere. Genotype I (GI) has replaced GIII as the dominant genotype in Asian countries during the past few decades, which caused considerable concerns about the potential change of epidemiology characteristics and the vaccine effectiveness. The aim of this study was to investigate the prevalence of JE neutralizing antibody and its waning antibody trend after live attenuated JE vaccine immunization. Additionally, this study analyzed the molecular characteristics of the E gene of Zhejiang Japanese encephalitis virus (JEV) strains, and established genetic relationships with other JEV strains.Conclusion/SignificancesJE neutralizing antibody positive rates increase in age ≥10 years old population, likely reflecting natural infection or natural boosting of immunity through exposure to wild virus. JE seropositivity rates were quite low in <35 years old age groups in Zhejiang Province. Waning of neutralizing antibody after live attenuated vaccine immunization was observed, but the clinical significance should be further investigated. Both the peripheral antibody response and genetic characterization indicate that current live attenuated JE vaccine conferred equal neutralizing potency against GI or GIII of wild strains. GI has replaced GIII as the dominant genotype in Zhejiang in the past few decades. Although the chance of exposure to wild JE virus has reduced, the virus still circulates in nature; therefore, it is necessary to implement immunization program for children continually and to conduct surveillance activity periodically.     

Epidemic of mumps in a partially immune population.

The incidence of mumps in vaccinated and nonvaccinated schoolchildren was studied after a recent epidemic. Information was collected by telephone interviews with the parents and a review of the physicians'' records. The vaccine appeared to be effective, for the incidence of mumps in the 145 vaccinated children--5.5%, or 8 cases--was significantly less (P less than 0.001) than the incidence in the 350 children considered susceptible to infection--21.7%, or 76 cases. The percentage of children who had been immunized decreased with increasing age, and acquisition of immunity through natural infection had the reverse trend; thus, the proportions of children susceptible to infection in each age group were about the same, and the age-specific attack rates were similar. Although the mothers were accurate in indicating absence of vaccination, they incorrectly indicated vaccination of their children 43.0% of the time; this error in reporting could influence vaccine administration in older children. Our findings suggest that mumps vaccination may substitute for natural illness in immunizing populations, and that more extensive use of the vaccine over a broader age range is required to prevent similar epidemics in the future.     

Protection against late-onset AIDS in macaques prophylactically immunized with a live simian HIV vaccine was dependent on persistence of the vaccine virus

This is a 5-year follow-up study on 12 macaques that were immunized orally with two live SHIV vaccines, six with V1 and six with V2. All 12 macaques became persistently infected after transient replication of the vaccine viruses; all were challenged vaginally 6 mo later with homologous pathogenic SHIV(KU-1). Two of the V1 group developed full-blown AIDS without evidence of vaccine virus DNA in tissues. The data on the 10 vaccinated survivors showed that all 10 became infected with SHIV(KU-1) and that DNA of both vaccine and SHIV(KU-1) viruses were present 6 mo postchallenge, with minimal replication of SHIV(KU-1). During the following 5 years, these animals remained persistently infected, but with only one of the two viruses. Six animals eliminated their vaccine virus after variable periods of time and four of these succumbed to reactivation of the challenge virus and AIDS. Five years after challenge, four latently infected animals, two with V2 and two with SHIV(KU-1), were reinoculated with SHIV(KU-1.) This resulted in transient superinfection and the animals promptly returned to their prechallenge status. Immunosuppression of the four animals 1 year later with Abs to CD8+ lymphocytes resulted in transiently productive replication of their respective latent viruses, and upon recovery of CD8+ lymphocytes, they reverted to their latent virus status. The major finding was that of eight animals that eliminated the vaccine virus, six developed AIDS. The two others harboring SHIV(KU-1) remain at risk for developing late-onset disease. The primary correlate against AIDS was persistence of the vaccine virus.     

Removal of gelatin from live vaccines and DTaP—an ultimate solution for vaccine-related gelatin allergy

From the early 1990s infants started to receive acellular pertussis vaccine combined with diphtheria and tetanus toxoids (DTaP) before live vaccines such as measles, rubella, and mumps vaccines, which contained gelatin as a stabilizer. Then, an increasing number of cases of anaphylactic/allergic reactions to those live vaccines were reported. Almost all these cases had a previous history of receiving three or four doses of DTaP containing gelatin.Anaphylactic/allergic reactions to live measles vaccine were analyzed using information obtained from the Reporting System, a retrospective study, as well as from the Monitoring System, a prospective study. Dramatic decreases in anaphylactic/allergic reactions to live measles vaccines were observed immediately after each manufacturer marketed gelatin-free or gelatin (hypo-allergic)-containing live measles vaccine, and since the end of 1998 reports on anaphylactic/allergic reactions to live measles vaccine have almost ceased.     

Immunogenicity and adverse reactions of influenza vaccination in elderly patients given acetaminophen or placebo

The objective was to examine the antibody responses to influenza immunization in an elderly population and the effect of prophylactic acetaminophen on adverse responses due to inactivated whole virus vaccine containing influenza A (H3N2 and H1N1) and B antigens. During the autumn of 1990, 100 patients 65 years or older were immunized and randomly allocated to receive placebo or 1,950 mg (2 x 975 mg) of acetaminophen. They recorded any local and systemic side effects over a 3-day period. Serology was performed on pre- and post (4-6 weeks) -vaccination sera. Age and gender distribution in the study were: 47% who were 75 years or older, and 61% of the patients were female. Most of the patients (97%) had pre-existing antibodies to Influenza A or B. Average peak preimmunization antibody titers were 40 to B Yamagata and A Taiwan (H1N1) and 80 for A Shanghai (H3N2). Half of each treatment group had a 4-fold or greater rise in antibody titer in response to the vaccine. Only 30% of patients immunized the previous year but 80% of those never vaccinated previously demonstrated a 4-fold or greater serological response to the vaccine. However, measurement of protection rates (HI >/= 40) before and after vaccination indicated 81.1-100% protection for the 3 viruses not influenced by treatment, gender or a history of previous vaccination. Both treatment groups had equally small numbers of patients who recorded systemic symptoms of drowsiness, myalgia, fever and chills and about 50% had arm soreness. Although about 80% of previously unimmunized adults mounted a 4-fold antibody rise to influenza vaccine antigens whereas booster effects were seen in only 30% of those immunized the previous year, protection rates were high (81-100%) after immunization and were not affected by acetaminophen treatment. Adverse effects (15% systemic and 50% local) were not ameliorated by 1950 mg of acetaminophen in these elderly patients.     

Predictors of the uptake of A (H1N1) influenza vaccine: findings from a population-based longitudinal study in Tokyo

Background

Overall pandemic A (H1N1) influenza vaccination rates remain low across all nations, including Japan. To increase the rates, it is important to understand the motives and barriers for the acceptance of the vaccine. We conducted this study to determine potential predictors of the uptake of A (H1N1) influenza vaccine in a cohort of Japanese general population.

Methodology/Principal Findings

By using self-administered questionnaires, this population-based longitudinal study was conducted from October 2009 to April 2010 among 428 adults aged 18–65 years randomly selected from each household residing in four wards and one city in Tokyo. Multiple logistic regression analyses were performed. Of total, 38.1% of participants received seasonal influenza vaccine during the preceding season, 57.0% had willingness to accept A (H1N1) influenza vaccine at baseline, and 12.1% had received A (H1N1) influenza vaccine by the time of follow-up. After adjustment for potential confounding variables, people who had been vaccinated were significantly more likely to be living with an underlying disease (p = 0.001), to perceive high susceptibility to influenza (p = 0.03), to have willingness to pay even if the vaccine costs ≥ US$44 (p = 0.04), to have received seasonal influenza vaccine during the preceding season (p<0.001), and to have willingness to accept A (H1N1) influenza vaccine at baseline (p<0.001) compared to those who had not been vaccinated.

Conclusions/Significance

While studies have reported high rates of willingness to receive A (H1N1) influenza vaccine, these rates may not transpire in the actual practices. The uptake of the vaccine may be determined by several potential factors such as perceived susceptibility to influenza and sensitivity to vaccination cost in general population.     

Effectiveness of the 2012/13 Trivalent Live and Inactivated Influenza Vaccines in Children and Adolescents in Saxony-Anhalt,Germany: A Test-Negative Case-Control Study

A live attenuated influenza vaccine has been available in Germany since the influenza season 2012/13, which is approved for children aged 2-17 years. Using data from our laboratory-based surveillance system, we described the circulation of influenza and non-influenza respiratory viruses during the influenza season 2012/13 in Saxony-Anhalt. We estimated the effectiveness of live and inactivated trivalent influenza vaccines in preventing laboratory-confirmed cases among children and adolescents. From week 40/2012 to 19/2013, sentinel paediatricians systematically swabbed acute respiratory illness patients for testing of influenza and 5 non-influenza viruses by PCR. We compared influenza cases and influenza-negative controls. Among children aged 2-17 years, we calculated overall and vaccine type-specific effectiveness against laboratory-confirmed influenza, stratified by age group (2-6; 7-17 years). We used multivariable logistic regression to adjust estimates for age group, sex and month of illness. Out of 1,307 specimens, 647 (35%) were positive for influenza viruses and 189 (15%) for at least one of the tested non-influenza viruses. For vaccine effectiveness estimation, we included 834 patients (mean age 7.3 years, 53% males) in our analysis. Of 347 (42%) influenza-positive specimens, 61 (18%) were positive for A(H1N1)pdm09, 112 (32%) for A(H3N2) and 174 (50%) for influenza B virus. The adjusted overall vaccine effectiveness including both age groups was 38% (95% CI: 0.8-61%). The adjusted effectiveness for inactivated vaccines was 37% (95% CI: -35-70%) and for live vaccines 84% (95% CI: 45-95%). Effectiveness for the live vaccine was higher in 2-6 year-old children (90%, 95% CI: 20-99%) than in children aged 7-17 years (74%, 95% CI: -32-95%). Our study of the strong influenza season in 2012/13 suggests a high preventive effect of live attenuated influenza vaccine especially among young children, which could not be reached by inactivated vaccines. We recommend the use of live attenuated influenza vaccines in children unless there are contraindications.     

The reactogenicity and immunogenicity of the Urabe Am 9 live mumps vaccine and persistence of vaccine induced antibodies in healthy young children

The immunogenicity and reactogenicity of the Urabe Am 9 mumps virus vaccine strain were studied after the administration of different doses of the vaccine to 197 children ranging in age from seven and a half months to nine years and without a history of mumps. There was no effect of dose on the response in serum neutralizing antibodies in the range of 10(2.9) to 10(4.7) TCID50/dose. In the 90 subjects without detectable serum neutralization antibodies before vaccination seroconversion was obtained in 94.4% after 42 days. Half of a group of 34 seropositive children who were tested also showed a fourfold or greater rise in antibodies. Persistence of vaccine-enhanced haemagluttinin-inhibition (EHI) antibodies was satisfactory as only two of 46 vaccinees followed-up for between 27 and 32 months had undetectable levels of EHI antibodies and the geometric mean titre of vaccine-induced EHI antibodies had only fallen to about one-third by 32 months after vaccination. Although there was serological evidence of a subclinical re-infection in three subjects, to date none of the vaccinees has had clinical mumps indicating that the vaccine confers protection against disease. The vaccine was well tolerated. Furthermore, the majority of the few 'reactions' reported were probably not vaccine-related. It is concluded that the Urabe Am 9 is an acceptable strain for use in live mumps vaccines.     

The Aggregation of Four Reconstructed Zygotes is the Limit to Improve the Developmental Competence of Cloned Equine Embryos

Embryo aggregation has been demonstrated to improve cloning efficiency in mammals. However, since no more than three embryos have been used for aggregation, the effect of using a larger number of cloned zygotes is unknown. Therefore, the goal of the present study was to determine whether increased numbers of cloned aggregated zygotes results in improved in vitro and in vivo embryo development in the equine. Zona-free reconstructed embryos (ZFRE''s) were cultured in the well of the well system in four different experimental groups: I. 1x, only one ZFRE per microwell; II. 3x, three per microwell; III. 4x, four per microwell; and IV. 5x, five ZFRE''s per microwell. Embryo size was measured on day 7, after which blastocysts from each experimental group were either a) maintained in culture from day 8 until day 16 to follow their growth rates, b) fixed to measure DNA fragmentation using the TUNEL assay, or c) transferred to synchronized mares. A higher blastocyst rate was observed on day 7 in the 4x group than in the 5x group. Non-aggregated embryos were smaller on day 8 compared to those aggregated, but from then on the in vitro growth was not different among experimental groups. Apoptotic cells averaged 10% of total cells of day 8 blastocysts, independently of embryo aggregation. Only pregnancies resulting from the aggregation of up to four embryos per microwell went beyond the fifth month of gestation, and two of these pregnancies, derived from experimental groups 3x and 4x, resulted in live cloned foals. In summary, we showed that the in vitro and in vivo development of cloned zona-free embryos improved until the aggregation of four zygotes and declined when five reconstructed zygotes were aggregated.     

Expectations of assisted conception for infertility.

OBJECTIVE--To provide reliable prognostic information for couples seeking assisted conception. DESIGN--Analysis of four years'' practice (1988-91). SETTING--Private university service linked with NHS reproductive medicine services. PATIENTS--804 couples with various causes of subfertility, median duration five years, median age of women 34 years. INTERVENTIONS--1280 completed cycles: 950 in vitro fertilisation, 144 gamete intrafallopian transfer, and 186 intrauterine insemination and superovulation. MAIN OUTCOME MEASURES--Pregnancy and birth rates per cycle and cumulative pregnancy and take home baby rates per couple. RESULTS--In women under 40 years and men with normal sperm, whatever the cause of infertility, results with in vitro fertilisation improved steadily reaching a pregnancy rate per cycle of 30% (95% confidence interval 26% to 35%) during 1990-1 and birth rate per cycle of 29% (23% to 35%) in 1990. Pregnancy and birth rates for gamete intrafallopian transfer were 36% (28% to 44%) and 26% (17% to 37%) and for intrauterine insemination 18% (12% to 24%) and 16% (10% to 22%). After six cycles cumulative probability of pregnancy was 82% and cumulative take home baby rate 70%. Considering only in vitro fertilisation and gamete intrafallopian transfer after four cycles the pregnancy rate was 78% (66% to 91%). CONCLUSIONS--Conception is less likely in women over 40 and men with sperm dysfunction. For other couples the prognosis for a live birth is at least as good as for fertile couples if they persist with treatment.     

Interference between strains in live virus vaccines, I: Combined vaccination with measles, mumps and rubella vaccine

One to four different lots of four commercially available trivalent measles-mumps-rubella vaccines were tested for their efficacy as measured by the induction of antibodies to the three vaccine viruses. All of the products were satisfactory although a 100% seroconversion rate was attained regularly only with rubella vaccine. The live virus in the different measles and mumps vaccine components and especially the relative amounts of measles to mumps virus varied widely. Obviously, the efficacy of a vaccine should not be judged only by the virus content. Of main importance is the further adjustment of the dosage of the interfering vaccine virus strains in relation to their attenuation.     

Review of dengue virus and the development of a vaccine

Dengue viral infection has become an increasing global health concern with over two-fifths of the world's population at risk of infection. It is the most rapidly spreading vector borne disease, attributed to changing demographics, urbanization, environment, and global travel. It continues to be a threat in over 100 tropical and sub-tropical countries, affecting predominantly children. Dengue also carries a hefty financial burden on the health care systems in affected areas, as those infected seek care for their symptoms. The search for a suitable vaccine for dengue has been ongoing for the last sixty years, yet any effective treatment or vaccine remains elusive. A vaccine must be protective for all four serotypes of dengue and be cost-effective. Many approaches to developing candidate vaccines have been employed. The candidates include live attenuated tetravalent vaccines, chimeric tetravalent vaccines based on attenuated dengue virus or Yellow Fever 17D, and recombinant DNA vaccines based on flavivirus and non-flavivirus vectors. This review outlines the challenges involved in dengue vaccine development and presents the current stages of proposed vaccine candidate development.