The Experts below are selected from a list of 8973 Experts worldwide ranked by ideXlab platform
Philippe Beutels - One of the best experts on this subject based on the ideXlab platform.
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herpes zoster risk reduction through exposure to Chickenpox patients a systematic multidisciplinary review
PLOS ONE, 2013Co-Authors: Benson Ogunjimi, Pierre Van Damme, Philippe BeutelsAbstract:Varicella-zoster virus (VZV) causes Chickenpox and may subsequently reactivate to cause herpes zoster later in life. The exogenous boosting hypothesis states that re-exposure to circulating VZV can inhibit VZV reactivation and consequently also herpes zoster in VZV-immune individuals. Using this hypothesis, mathematical models predicted widespread Chickenpox vaccination to increase herpes zoster incidence over more than 30 years. Some countries have postponed universal Chickenpox vaccination, at least partially based on this prediction. After a systematic search and selection procedure, we analyzed different types of exogenous boosting studies. We graded 13 observational studies on herpes zoster incidence after widespread Chickenpox vaccination, 4 longitudinal studies on VZV immunity after re-exposure, 9 epidemiological risk factor studies, 7 mathematical modeling studies as well as 7 other studies. We conclude that exogenous boosting exists, although not for all persons, nor in all situations. Its magnitude is yet to be determined adequately in any study field.
Benson Ogunjimi - One of the best experts on this subject based on the ideXlab platform.
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herpes zoster risk reduction through exposure to Chickenpox patients a systematic multidisciplinary review
PLOS ONE, 2013Co-Authors: Benson Ogunjimi, Pierre Van Damme, Philippe BeutelsAbstract:Varicella-zoster virus (VZV) causes Chickenpox and may subsequently reactivate to cause herpes zoster later in life. The exogenous boosting hypothesis states that re-exposure to circulating VZV can inhibit VZV reactivation and consequently also herpes zoster in VZV-immune individuals. Using this hypothesis, mathematical models predicted widespread Chickenpox vaccination to increase herpes zoster incidence over more than 30 years. Some countries have postponed universal Chickenpox vaccination, at least partially based on this prediction. After a systematic search and selection procedure, we analyzed different types of exogenous boosting studies. We graded 13 observational studies on herpes zoster incidence after widespread Chickenpox vaccination, 4 longitudinal studies on VZV immunity after re-exposure, 9 epidemiological risk factor studies, 7 mathematical modeling studies as well as 7 other studies. We conclude that exogenous boosting exists, although not for all persons, nor in all situations. Its magnitude is yet to be determined adequately in any study field.
Nobumichi Kobayashi - One of the best experts on this subject based on the ideXlab platform.
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role of meteorological conditions in reported Chickenpox cases in wuhan and hong kong china
BMC Infectious Diseases, 2017Co-Authors: Banghua Chen, Ayako Sumi, Lei Wang, Wang Zhou, Nobumichi KobayashiAbstract:Chickenpox is a common contagious disease that remains an important public health issue worldwide. Over 90% of unvaccinated individuals become infected, but infection occurs at different ages in different parts of the world. Many people have been infected by 20 to 30 years of age in China, and adults and pregnant women who become infected often develop severe infection. Furthermore, a mortality rate of 2–3 per 100,000 infected persons has been reported. In this study, we explore the temperature-dependent transition of patterns of reported Chickenpox cases in two large subtropical climate cities, Wuhan and Hong Kong, China, to aid in the prediction of epidemics and preparation for the effects of climatic changes on epidemiology of Chickenpox in China. We used a time series analysis comprising a spectral analysis based on the maximum entropy method in the frequency domain and the nonlinear least squares method in the time domain. Specifically, the following time series data were analyzed: data of reported Chickenpox cases and meteorological data, including the mean temperature, relative humidity and total rainfall in Wuhan and Hong Kong from January 2008 to June 2015. The time series data of Chickenpox for both Wuhan and Hong Kong have two peaks per year, one in winter and another in spring, indicating a bimodal cycle. To investigate the source of the bimodal cycle of the Chickenpox data, we defined the contribution ratio of the 1-year cycle, Q 1, and the 6-month cycle, Q 2, as the contribution of the amplitude of a 1-year cycle and a 6-month cycle, respectively, to the entire amplitude of the time-series data. The Q 1 values of Wuhan and Hong Kong were positively correlated with the annual mean temperature and rainfall of each city. Conversely, the Q 2 values of Wuhan and Hong Kong were negatively correlated with the annual mean temperature and rainfall of Wuhan and Hong Kong. Our results showed that the mean temperature and rainfall have a significant influence on the incidence of Chickenpox, and might be important predictors of Chickenpox incidence in Wuhan and Hong Kong.
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the role of temperature in reported Chickenpox cases from 2000 to 2011 in japan
Epidemiology and Infection, 2015Co-Authors: K Harigane, Ayako Sumi, Keiji Mise, Nobumichi KobayashiAbstract:Annual periodicities of reported Chickenpox cases have been observed in several countries. Of these, Japan has reported a two-peaked, bimodal annual cycle of reported Chickenpox cases. This study investigated the possible underlying association of the bimodal cycle observed in the surveillance data of reported Chickenpox cases with the meteorological factors of temperature, relative humidity and rainfall. A time-series analysis consisting of the maximum entropy method spectral analysis and the least squares method was applied to the Chickenpox data and meteorological data of 47 prefectures in Japan. In all of the power spectral densities for the 47 prefectures, the spectral lines were observed at the frequency positions corresponding to the 1-year and 6-month cycles. The optimum least squares fitting (LSF) curves calculated with the 1-year and 6-month cycles explained the underlying variation of the Chickenpox data. The LSF curves reproduced the bimodal and unimodal cycles that were clearly observed in northern and southern Japan, respectively. The data suggest that the second peaks in the bimodal cycles in the reported Chickenpox cases in Japan occurred at a temperature of approximately 8·5 °C.
David Isaacs - One of the best experts on this subject based on the ideXlab platform.
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the management of varicella zoster virus exposure and infection in pregnancy and the newborn period
The Medical Journal of Australia, 2001Co-Authors: Annemarie Heuchan, David IsaacsAbstract:○ Zoster immunoglobulin (ZIG) should be offered to pregnant, varicella-seronegative women with significant exposure to varicella-zoster virus (VZV) (Chickenpox) infection. ○ Oral aciclovir prophylaxis should be considered for susceptible pregnant women exposed to VZV who did not receive ZIG or have risk factors for severe disease. ○ Intravenous aciclovir should be given to pregnant women who develop complicated varicella at any stage of pregnancy. ○ Counselling on the risk of congenital varicella syndrome is recommended for pregnant women who develop Chickenpox. ○ ZIG should be given to a baby whose mother develops Chickenpox up to 7 days before delivery or up to 28 days after delivery. ○ Intravenous aciclovir should be given to babies presenting unwell with Chickenpox, whether or not they received ZIG. ○ Breastfeeding of babies infected with or exposed to VZV is encouraged. ○ A mother with Chickenpox or zoster does not need to be isolated from her own baby. ○ If siblings at home have Chickenpox, a newborn baby should be given ZIG if its mother is seronegative. ○ The newborn baby does not need to be isolated from its siblings with Chickenpox, whether or not the baby was given ZIG. ○ After significant nursery exposure to VZV, ZIG should be given to seronegative babies and to all babies born before 28 weeks' gestation.
Alexander Doroshenko - One of the best experts on this subject based on the ideXlab platform.
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what we know now an economic evaluation of Chickenpox vaccination and dose timing using an agent based model
Value in Health, 2020Co-Authors: Ellen Rafferty, Wade Mcdonald, Nathaniel D Osgood, Alexander Doroshenko, Marwa FaragAbstract:Abstract Objectives The value of Chickenpox vaccination is still debated in the literature and by jurisdictions worldwide. This uncertainty is reflected in the inconsistent uptake of the vaccine, where some countries offer routine childhood immunization programs, others have targeted programs, and in many the vaccine is only privately available. Even across the countries that have universal funding for the vaccine, there is a diversity of schedules and dosing intervals. Using an agent-based model of Chickenpox and shingles, we conducted an economic evaluation of Chickenpox vaccination in Alberta, Canada. Methods We compared the cost-effectiveness of 2 common Chickenpox vaccination schedules, specifically a long dosing interval (first dose: 12 months; second dose: 4-6 years) and a short dosing interval (first dose: 12 months; second dose: 18 months). Results The economic evaluation demonstrated a shorter dosing interval may be marginally preferred, although it consistently led to higher costs from both the societal and healthcare perspectives. We found that Chickenpox vaccination would be cost-saving and highly cost-effective from the societal and healthcare perspective, assuming there was no impact on shingles. Conclusion Chickenpox vaccine was cost-effective when not considering shingles and remained so even if there was a minor increase in shingles following vaccination. However, if Chickenpox vaccination did lead to a substantial increase in shingles, then Chickenpox vaccination was not cost-effective from the healthcare perspective.
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seeking the optimal schedule for Chickenpox vaccination in canada using an agent based model to explore the impact of dose timing coverage and waning of immunity on disease outcomes
Vaccine, 2020Co-Authors: Ellen Rafferty, Wade Mcdonald, Nathaniel D Osgood, Weicheng Qian, Alexander DoroshenkoAbstract:Abstract Many countries continue to consider implementing a universal Chickenpox vaccine program; however, there is no consensus on the most appropriate and effective timing between vaccine doses. The Chickenpox vaccine schedule debate is highlighted in Canada, where there are currently eight different vaccine schedules across the country. The objective of this study was to test the overall effectiveness of Chickenpox vaccination, as well as the specific impact of two different vaccine schedules, on Chickenpox disease outcomes in Alberta over 75 years. Using an agent-based model of Chickenpox disease, we tested the impact of three vaccination scenarios including: baseline (no vaccination), a long dosing interval-Schedule LDI (1st dose – 12 months; 2nd dose – 4-6 years) and a short dosing interval-Schedule SDI (1st dose – 12 months; 2nd dose – 18 months) on Chickenpox and shingles disease outcomes. Chickenpox vaccination led to a substantial decrease in Chickenpox incidence over 75 years post-vaccine implementation. Compared to Schedule LDI, Schedule SDI resulted in a significantly lower Chickenpox incidence, a higher age of Chickenpox infection, a lower Chickenpox breakthrough rate and a higher shingles incidence rate. Our model findings suggest that the Chickenpox vaccine is effective over a long period of time and the dose timing of the vaccine may impact disease outcomes and vaccine effectiveness. However, the effectiveness of the vaccine dose timing is only one consideration for policy-makers who are implementing a Chickenpox vaccine program, with others including risk of adverse events, the impact of the schedule on other antigens in a combination vaccine, parental acceptance and the cost associated with different schedules.
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evaluation of the effect of Chickenpox vaccination on shingles epidemiology using agent based modeling
PeerJ, 2018Co-Authors: Ellen Rafferty, Wade Mcdonald, Nathaniel D Osgood, Weicheng Qian, Alexander DoroshenkoAbstract:Background Biological interactions between varicella (Chickenpox) and herpes zoster (shingles), two diseases caused by the varicella zoster virus (VZV), continue to be debated including the potential effect on shingles cases following the introduction of universal childhood Chickenpox vaccination programs. We investigated how Chickenpox vaccination in Alberta impacts the incidence and age-distribution of shingles over 75 years post-vaccination, taking into consideration a variety of plausible theories of waning and boosting of immunity. Methods We developed an agent-based model representing VZV disease, transmission, vaccination states and coverage, waning and boosting of immunity in a stylized geographic area, utilizing a distance-based network. We derived parameters from literature, including modeling, epidemiological, and immunology studies. We calibrated our model to the age-specific incidence of shingles and Chickenpox prior to vaccination to derive optimal combinations of duration of boosting (DoB) and waning of immunity. We conducted paired simulations with and without implementing Chickenpox vaccination. We computed the count and cumulative incidence rate of shingles cases at 10, 25, 50, and 75 years intervals, following introduction of vaccination, and compared the difference between runs with vaccination and without vaccination using the Mann-Whitney U-test to determine statistical significance. We carried out sensitivity analyses by increasing and lowering vaccination coverage and removing biological effect of boosting. Results Chickenpox vaccination led to a decrease in Chickenpox cases. The cumulative incidence of Chickenpox had dropped from 1,254 cases per 100,000 person-years pre Chickenpox vaccination to 193 cases per 100,000 person-years 10 years after the vaccine implementation. We observed an increase in the all-ages shingles cumulative incidence at 10 and 25 years post Chickenpox vaccination and mixed cumulative incidence change at 50 and 75 years post-vaccination. The magnitude of change was sensitive to DoB and ranged from an increase of 22-100 per 100,000 person-years at 10 years post-vaccination for two and seven years of boosting respectively (p < 0.001). At 75 years post-vaccination, cumulative incidence ranged from a decline of 70 to an increase of 71 per 100,000 person-years for two and seven years of boosting respectively (p < 0.001). Sensitivity analyses had a minimal impact on our inferences except for removing the effect of boosting. Discussion Our model demonstrates that over the longer time period, there will be a reduction in shingles incidence driven by the depletion of the source of shingles reactivation; however in the short to medium term some age cohorts may experience an increase in shingles incidence. Our model offers a platform to further explore the relationship between Chickenpox and shingles, including analyzing the impact of different Chickenpox vaccination schedules and cost-effectiveness studies.