A Sample Guideline for Reverse Vaccinology Approach for the Development of Subunit Vaccine Using Varicella Zoster as a Model Disease

For the development of multi-peptide vaccine, identification of antigenic epitopes is crucial. If it is done using wet lab techniques, the identification process can be time-consuming, laborious, and cost-intensive. In silico tools, on the other hand, enable researchers to predict potential epitopes with little to no cost for further in vivo and in vitro testing. The rapid identification process using in silico tools helps in responding to health emergencies faster. Developing an efficient and high coverage vaccine is one of the ways to reduce morbidity and mortality rates of the diseases and protect the affected populations. In this chapter, we introduce the necessary tools and methodology for the identification and characterization of antigenic epitopes to design a multi-epitope vaccine using varicella-zoster virus as an example vector model.

Combined measles-mumps-rubella-varicella vaccine and febrile convulsions: the risk considered in the broad context

INTRODUCTION

Studies on quadrivalent measles, mumps, rubella, and varicella (MMRV) vaccines have indicated a twofold increased relative risk of febrile convulsion (FC) after the first dose compared to MMR and V administered at the same medical visit (MMR+V).

AREAS COVERED

This narrative review contextualizes FC occurrence after the first MMRV vaccine dose from a clinical perspective and outlines approaches to attenuate FC occurrence post-vaccination.

EXPERT OPINION

While the relative FC risk increases after the first dose of MMRV compared to MMR+V vaccine in measles-naïve infants, the attributable risk is low versus the overall FC risk in the pediatric population triggered by other causes, like natural exposure to pathogens or routine vaccination. No increased risk of FC has been reported after MMRV co-administration with other routine vaccines compared to MMRV alone. Based on our findings and considering the MMRV vaccination benefits (fewer injections, higher coverage, better vaccination compliance), the overall benefit-risk profile of MMRV vaccine is considered to remain positive. Potential occurrence of FC in predisposed children (e.g. with personal/family history of FC) may be attenuated if they receive MMR+V instead of MMRV as the first dose. It is also important to monitor vaccinees for fever during the first 2 weeks post-vaccination.

Seroprevalence of Varicella Zoster Virus in the Eastern Province of Saudi Arabia in Post-vaccination Era

Background

Varicella zoster virus (VZV) is a highly contagious virus causing two types of skin infections known as varicella and herpes zoster. Due to its high burden, vaccination is available in almost 42 counties worldwide including Saudi Arabia. Since its introduction, data on the impact of the vaccine from local and neighboring countries is lacking.

Objective

This study was done to determine the seroprevalence of anti VZV IgG and IgM antibodies in post-vaccination era fifteen years after varicella vaccine introduction in routine childhood vaccination schedules.

Methods

retrospective observational study over seven years on all individual tested for anti VZV IgG and IgM in a tertiary university hospital in the eastern province of Saudi Arabia between Jan 2014 to Dec 2020.

Results

83.69% (6820/8149) of tested population were seropositive with significantly lower positivity in children less than ten years old (44%). Yet no significant difference was found between males and females or among different nationalities tested. Conclusions: varicella continuous to be prevalent in the eastern province of Saudi Arabia fifteen years after the introduction of the vaccine but the level of anti VZV IgG detection is significantly lower in children below ten years of age. Further large-scale studies are needed to assess the impact of universal vaccination on the epidemiology of VZV.

Assessing vaccine effectiveness for varicella in Wuxi, China: a time-series analysis

OBJECTIVE

The varicella vaccine is not included in the national childhood immunization schedules in China. Varicella epidemics and outbreaks are frequently reported, and the evidence for the effectiveness of the varicella vaccine remains unclear. The aim of this study was to investigate varicella vaccine effectiveness in Wuxi, China.

METHODS

Varicella surveillance data were extracted from the China Information System for Disease Control and Prevention, and vaccination data were obtained from the Vaccination Integrated Service Management Information System of Jiangsu Province, China. Time-series analysis approaches were used to estimate varicella vaccine effectiveness.

RESULTS

A total of 16,093 varicella cases among children aged 1-6 years between January 2016 and December 2020 were analysed. A total of 217,297 children completed a two-dose varicella vaccination series. Compared with districts with lower vaccination rates, districts in Wuxi with higher varicella vaccination rates had a lower proportion of cases (p < 0.001). In the time-series approach, 0.8% fewer varicella cases were associated with a 1% increase in the two-dose varicella vaccination rate (p < 0.001), and similar effects were found in both the male and female populations.

CONCLUSIONS

Two-dose varicella vaccination was recommended as an effective health intervention to prevent varicella in Wuxi, China. Varicella vaccination is urgently needed in routine childhood immunisation programs.

Varicella in the neonatal ICU due to the Varicella vaccine Oka strain

BACKGROUND

Varicella vaccination of non-immune post-partum women is recommended to reduce the risk of chickenpox in mothers and their infants. Though rare, transmission of the varicella vaccine strain vOka can occur from recent vaccinees to non-immune contacts who usually develop mild chickenpox.

METHODS/RESULTS

Here we describe an infant hospitalized in the neonatal ICU with vaccine-strain varicella due to transmission from their mother who received the varicella vaccine post-partum. We describe the infection prevention and control strategies implemented to prevent further transmission.

CONCLUSION

Vaccine-strain varicella transmission from mother to infant is a rare event and its occurrence in the neonatal ICU setting can be challenging. Anticipatory guidance for mothers vaccinated in the postpartum period and support of parents of an infected infant are recommended.

Common Features Between Stroke Following Varicella in Children and Stroke Following Herpes Zoster in Adults : Varicella-Zoster Virus in Trigeminal Ganglion

The cerebral arteries are innervated by afferent fibers from the trigeminal ganglia. Varicella-zoster virus (VZV) frequently resides in the trigeminal ganglion. Reports of arterial ischemic stroke due to VZV cerebral vasculopathy in adults after herpes zoster have been described for decades. Reports of arterial ischemic stroke due to post-varicella cerebral arteriopathy in children have also been described for decades. One rationale for this review has been post-licensure studies that have shown an apparent protective effect from stroke in both adults who have received live zoster vaccine and children who have received live varicella vaccine. In this review, we define common features between stroke following varicella in children and stroke following herpes zoster in adults. The trigeminal ganglion and to a lesser extent the superior cervical ganglion are central to the stroke pathogenesis pathway because afferent fibers from these two ganglia provide the circuitry by which the virus can travel to the anterior and posterior circulations of the brain. Based on studies in pseudorabies virus (PRV) models, it is likely that VZV is carried to the cerebral arteries on a kinesin motor via gE, gI and the homolog of PRV US9. The gE product is an essential VZV protein.

Changing Epidemiology of Varicella Outbreaks in the United States During the Varicella Vaccination Program, 1995-2019

We describe the changing epidemiology of varicella outbreaks informed by past and current active and passive surveillance in the United States by reviewing data published during 1995-2015 and analyzing new data from 2016 to 2019. Varicella outbreaks were defined as ≥5 varicella cases within 1 setting and ≥1 incubation period. During the 1-dose varicella vaccination program (1995‒2006), the number of varicella outbreaks declined by 80% (2003-2006 vs 1995-1998) in 1 active surveillance area where vaccination coverage reached 90.5% in 2006. During the 2-dose program, in 7 states with consistent reporting to the Centers for Disease Control and Prevention, the number of outbreaks declined by 82% (2016-2019 vs 2005-2006). Over the entire program (1995-2019), outbreak size and duration declined from a median of 15 cases/outbreak and 45 days duration to 7 cases and 30 days duration. The proportion of outbreaks with <10 cases increased from 28% to 73%. During 2016‒2019, most (79%) outbreak cases occurred among unvaccinated or partially vaccinated persons eligible for second-dose vaccination, highlighting the potential for further varicella control.

Health and Economic Impact of the United States Varicella Vaccination Program, 1996-2020

BACKGROUND

The aim of this study was to evaluate the health and economic impact of the varicella vaccination program on varicella disease in the United States (US), 1996-2020.

METHODS

Analysis was conducted using the Centers for Disease Control and Prevention or published annual population-based varicella incidence, and varicella-associated hospitalization, outpatient visit, and mortality rates in the US population aged 0-49 years during 1996-2020 (range, 199.5-214.2 million persons) compared to before vaccination (1990-1994). Disease costs were estimated using the societal perspective. Vaccination program costs included costs of vaccine, administration, postvaccination adverse events, and travel and work time lost to obtain vaccination. All costs were adjusted to 2020 US dollars using a 3% annual discount rate. The main outcome measures were the number of varicella-associated cases, hospitalizations, hospitalization days, and premature deaths prevented; life-years saved; and net societal savings from the US varicella vaccination program.

RESULTS

Among US persons aged 0-49 years, during 1996-2020, it is estimated that more than 91 million varicella cases, 238 000 hospitalizations, 1.1 million hospitalization days, and almost 2000 deaths were prevented and 118 000 life-years were saved by the varicella vaccination program, at net societal savings of $23.4 billion.

CONCLUSIONS

Varicella vaccination has resulted in substantial disease prevention and societal savings for the US over 25 years of program implementation.

Celebrating 25 Years of Varicella Vaccination Coverage for Children and Adolescents in the United States: A Success Story

Tracking vaccination coverage is a critical component of monitoring a vaccine program. Three different surveillance systems were used to examine trends in varicella vaccination coverage during the United States vaccination program: National Immunization Survey-Child, National Immunization Survey-Teen, and immunization information systems (IISs). The relationship of these trends to school requirements and disease decline was also examined. Among children aged 19-35 months, ≥1 dose of varicella vaccine increased from 16.0% in 1996 to 89.2% by the end of the 1-dose program in 2006, stabilizing around at least 90.0% thereafter. The uptake of the second dose was rapid after the 2007 recommendation. Two-dose coverage among children aged 7 years at 6 high-performing IIS sites increased from 2.6%-5.5% in 2006 to 86.0%-100.0% in 2020. Among adolescents aged 13-17 years, ≥2-dose coverage increased from 4.1% in 2006 to 91.9% in 2020. The proportion of adolescents with history of varicella disease declined from 69.9% in 2006 to 8.4% in 2020. In 2006, 92% of states and the District of Columbia (DC) had 1-dose daycare or school entry requirements; 88% of states and DC had 2-dose school entry requirements in the 2020-2021 school year. The successes in attaining and maintaining high vaccine coverage were paramount in the dramatic reduction of the varicella burden in the United States over the 25 years of the vaccination program, but opportunities remain to further increase coverage and decrease varicella morbidity and mortality.

Decline in Severe Varicella Disease During the United States Varicella Vaccination Program: Hospitalizations and Deaths, 1990-2019

To describe the impact of the US varicella vaccination program on severe varicella outcomes, we analyzed varicella hospitalizations using the National Inpatient Sample 1993-2019 and varicella deaths using the National Center for Health Statistics data 1990-2019. Over 25 years of vaccination program (1995-2019), varicella hospitalizations, and deaths declined 94% and 97%, respectively, among persons aged <50 years. Most of the decline (∼90%) occurred during the 1-dose period (through 2006/2007) by attaining and maintaining high vaccination coverage; additional declines occurred during the 2-dose period, especially in the age groups covered by the 2-dose recommendation. The greatest decline for both hospitalizations and deaths (97% and >99%, respectively) was among persons aged <20 years, born during the varicella vaccination program. In the <20 age group, varicella hospitalization has become a rare event, and varicella deaths have been practically eliminated in the United States. A total of >10 500 varicella hospitalizations and 100 varicella deaths are now prevented annually in the United States as a direct result of vaccination and reduction in varicella-zoster virus circulation.

Australian Paediatric Surveillance Unit (APSU) Annual Surveillance Report 2021

The Australian Paediatric Surveillance Unit (APSU) has been conducting surveillance of rare communicable and non-communicable conditions in children since its inception in 1993. In this report, the results are described of surveillance of ten communicable diseases (and complications) for 2021, including the numbers of cases and incidence estimates; demographics; clinical features; and management and short-term outcomes. The included diseases are: acute flaccid paralysis (AFP); congenital cytomegalovirus (CMV); neonatal herpes simplex virus (HSV) infection; paediatric human immunodeficiency virus (HIV) infection; perinatal exposure to HIV; severe complications from influenza; juvenile-onset respiratory papillomatosis (JoRRP); congenital rubella syndrome; congenital varicella syndrome; and neonatal varicella infection. In 2021, cases of JoRRP were reported to the APSU for the first time since 2017, indicating potential gaps in HPV vaccination. AFP surveillance by APSU again contributed to Australia achieving a minimum target incidence of one AFP case per 100,000 children aged < 15 years. There were no cases of children with severe complications of influenza. No cases of varicella or congenital rubella were reported; however, at-risk populations, especially young migrant and refugee women from countries without universal vaccination programs, need to be screened and prioritised for vaccination prior to pregnancy. Cases of perinatal exposure to HIV continue to increase; however, the rate of mother-to-child-transmission remains at low levels due to the use of effective intervention strategies. Case numbers of congenital CMV and neonatal HSV remain steady in the absence of vaccines, prompting the need for greater awareness and education, with recent calls for target screening of at-risk infants for congenital CMV.

Identifying optimal vaccination scenarios to reduce varicella zoster virus transmission and reactivation

BACKGROUND

Varicella zoster virus (VZV) is one of the eight known human herpesviruses. Initial VZV infection results in chickenpox, while viral reactivation following a period of latency manifests as shingles. Separate vaccines exist to protect against both initial infection and subsequent reactivation. Controversy regarding chickenpox vaccination is contentious with most countries not including the vaccine in their childhood immunization schedule due to the hypothesized negative impact on immune-boosting, where VZV reactivation is suppressed through exogenous boosting of VZV antibodies from exposure to natural chickenpox infections.

METHODS

Population-level chickenpox and shingles notifications from Thailand, a country that does not vaccinate against either disease, were previously fitted with mathematical models to estimate rates of VZV transmission and reactivation. Here, multiple chickenpox and shingles vaccination scenarios were simulated and compared to a model lacking any vaccination to analyze the long-term impacts of VZV vaccination.

RESULTS

As expected, simulations suggested that an introduction of the chickenpox vaccine, at any coverage level, would reduce chickenpox incidence. However, chickenpox vaccine coverage levels above 35% would increase shingles incidence under realistic estimates of shingles coverage with the current length of protective immunity from the vaccine. A trade-off between chickenpox and shingles vaccination coverage was discovered, where mid-level chickenpox coverage levels were identified as the optimal target to minimize total zoster burden. Only in scenarios where shingles vaccine provided lifelong immunity or coverage exceeded current levels could large reductions in both chickenpox and shingles be achieved.

CONCLUSIONS

The complicated nature of VZV makes it impossible to select a single vaccination scenario as universal policy. Strategies focused on reducing both chickenpox and shingles incidence, but prioritizing the latter should maximize efforts towards shingles vaccination, while slowly incorporating chickenpox vaccination. Alternatively, countries may wish to minimize VZV complications of both chickenpox and shingles, which would lead to maximizing vaccine coverage levels across both diseases. Balancing the consequences of vaccination to overall health impacts, including understanding the impact of an altered mean age of infection for both chickenpox and shingles, would need to be considered prior to any vaccine introduction.

Relative efficacy of varicella vaccines: network meta-analysis of randomized controlled trials

OBJECTIVE

Although varicella vaccination is highly effective, no head-to-head randomized controlled trials (RCTs) have compared the efficacy of different vaccine formulations. This study assessed the relative efficacy of different varicella vaccines using network meta-analysis (NMA).

METHODS

We estimated the relative efficacies of varicella vaccines and dosing regimens from RCTs using Bayesian NMA. Modeling-based time-series NMA (MBNMA) was performed, accounting for differences in time since vaccination, to extrapolate long-term vaccine efficacy (VE).

RESULTS

Eight RCTs were included based on systematic review of biomedical databases. Efficacy data were reported for four varicella-containing vaccines: Varivax (V-MSD, one and two dose), Varilrix (V-GSK, one dose), Priorix-Tetra (MMRV-GSK, one dose), and Sinovac (V-Sinovac, one dose). All varicella vaccines were effective versus no vaccination. Two-dose V-MSD (98.29%, 95% credible interval [CrI] 96.08-99.23) showed significantly higher VE versus all one-dose varicella-containing vaccines, but no significant difference versus two-dose MMRV-GSK (95.19%, 95% CrI 90.3-97.63). Two-dose MMRV-GSK showed higher VE than one-dose V-GSK (66.47%; 95% CrI 43.02-79.43), but no significant differences in VE versus one-dose V-MSD or one-dose V-Sinovac. In one-dose comparisons, V-MSD showed significantly higher VE (93.09%, 95% CrI 89.13-95.96) than V-GSK, but no significant difference versus V-Sinovac (89.22%; 95% CrI 67.1-96.5). MBNMA indicated that protection against varicella was sustained without waning over the 10 year follow-up.

CONCLUSIONS

Our study reported higher VE for two-dose V-MSD and MMRV-GSK. Among one-dose formulations, one-dose V-MSD was more efficacious than one-dose V-GSK. Policymakers should take into consideration differences in VE when implementing one- versus two-dose strategies in universal vaccination programs.

Varicella outbreaks in schools and kindergartens in Shanghai, China from 2011 to 2020

Background

Varicella is a contagious disease caused by varicella-zoster virus and varicella vaccine (VarV) is the most effective way to prevent and control varicella. Despite high VarV coverage there were still varicella outbreaks in schools and kindergartens. We aim to analyze the epidemiological characteristics of varicella outbreaks in Huangpu District, Shanghai, China from 2011 to 2020.

Methods

For varicella outbreaks, case information and vaccination history were collected. Mann–Kendall test and descriptive methods were used to analyzed the trend and epidemiological catachrestic of varicella outbreaks.

Results

A total of 57 varicella outbreaks were reported from 2011 to 2020, including 30 outbreaks (52.6%) in primary schools. The results of the Mann–Kendall trend test (z = 1.97, p = 0.049) showed an upward trend in the number of cases during the study period, but the trend change was not statistically significant. Emergency vaccination was carried out in 42 (73.7%) outbreaks which influenced the duration of the epidemic (F = 4.53, p = 0.0379). A total of 573 varicella cases were reported, including 357 cases (62.3%) who had received at least one dose of varicella vaccine.

Conclusions

The number of varicella outbreaks has not changed significantly in the decade from 2011 to 2020. The strategy of varicella vaccination, the development and application of varicella vaccine, and the control measures after the occurrence of varicella outbreaks need to be optimized. In addition to vaccination, as a disease transmitted by contact, quarantine measures, good personal hygiene, environmental disinfection, and ventilation are also important.

Recognition & management of varicella infections and accuracy of antimicrobial recommendations: Case vignettes study in the US

Background

In 1995, the CDC recommended one-dose routine varicella immunization for children <12 years of age, expanding its recommendation to two doses in 2006. Today, with widespread varicella vaccination coverage, an estimated 3.5 million cases of varicella, 9,000 hospitalizations, and 100 deaths are prevented annually in the United States. Since varicella infections are now uncommon, health care providers (HCPs) may not recognize varicella infections and may prescribe inappropriate treatment.

Methods

An online survey of HCPs was conducted to assess recognition and management of varicella infections. Responses to eight varicella vignettes describing patients with varying varicella symptoms were analyzed and descriptive analyses performed. Stratified analysis comparing responses of those licensed before and in/after 1996 was also performed.

Results

153 HCPs (50 nurse practitioners, 103 doctors) completed the survey. Mean age of respondents was 44 years. 62% were female, and 82% were licensed before 1996. Varicella infection was correctly diagnosed 79% of the time. HCPs correctly recognized uncomplicated varicella vignettes 85% of the time versus 61% of the time for complicated varicella vignettes. Antibiotics were recommended 17% of the time and antivirals 18% of the time, of which 25% and 69% (respectively) were not appropriate per guidelines. HCPs licensed before 1996 were better able to recognize varicella compared to those licensed later, but prescribed more antimicrobials medications to treat varicella.

Conclusions

Although most HCPs recognized varicella infection, a sizable proportion could not recognize cases with complications, and some of the varicella cases were inappropriately treated with antibiotics and/or antivirals. Additional HCP training and high vaccination coverage are important strategies to avoid inaccurate diagnoses and minimize unnecessary exposure to antimicrobial/antiviral therapies.

Comparison of performance of varicella vaccines via infectious disease modeling

BACKGROUND

Population-level infectious disease models for varicella require vaccine parameters, namely 'take' and 'duration of protection' (defined here as vaccine performance), to quantify the impact of vaccination. Current published models for varicella use vaccine parameters derived from various methodologies which does not allow for the direct comparison of different vaccines.

METHODS

We estimated take and duration of protection using deterministic compartmental models to simulate clinical trials of one- or two-dose varicella vaccination using Varivax® (V-MSD) and Varilrix® (V-GSK). We fit different models to clinical trial data on breakthrough infections and evaluated their respective goodness-of-fit using the Akaike Information Criterion (AIC).

RESULTS

Based upon the clinical trial data, we estimated that 90.3% (95% CI: 87.8-92.9%) of the cohort gained permanent protection from breakthrough varicella after the first dose of V-MSD compared to 61.7% (95% CI: 58.2-65.3%) with the first dose of V-GSK. We further estimated that a total of 97.0% (95% CI: 95.2-98.8%) and 93.8% (95% CI: 92.2-95.4%) of the cohort were permanently protected after two-doses of V-MSD and V-GSK, respectively. According to the AIC, our new model (V-MSD AIC = 92.7; V-GSK AIC = 170.3) provided a better fit than an existing model (V-MSD AIC = 108.9; V-GSK AIC = 216.1).

CONCLUSIONS

The model developed fits the long-term clinical trial data on breakthrough infections for both V-MSD and V-GSK, thus, allowing for the direct comparison of vaccine performance. We estimated that a single dose of V-MSD was more likely to provide permanent protection than a single dose of V-GSK, while the protection offered by two doses was similar for both vaccines.

Impact of universal varicella vaccination on the use and cost of antibiotics and antivirals for varicella management in the United States

Background

Our objective was to estimate the impact of universal varicella vaccination (UVV) on the use and costs of antibiotics and antivirals for the management of varicella among children in the United States (US).

Methods

A decision tree model of varicella vaccination, infections and treatment decisions was developed. Results were extrapolated to the 2017 population of 73.5 million US children. Model parameters were populated from published sources. Treatment decisions were derived from a survey of health care professionals’ recommendations. The base case modelled current vaccination coverage rates in the US with additional scenarios analyses conducted for 0%, 20%, and 80% coverage and did not account for herd immunity benefits.

Results

Our model estimated that 551,434 varicella cases occurred annually among children ≤ 18 years in 2017. Antivirals or antibiotics were prescribed in 23.9% of cases, with unvaccinated children receiving the majority for base case. The annual cost for varicella antiviral and antibiotic treatment was approximately $14 million ($26 per case), with cases with no complications accounting for $12 million. Compared with the no vaccination scenario, the current vaccination rates resulted in savings of $181 million (94.7%) for antivirals and $78 million (95.0%) for antibiotics annually. Scenario analyses showed that higher vaccination coverage (from 0% to 80%) resulted in reduced annual expenditures for antivirals (from $191 million to $41 million), and antibiotics ($82 million to $17 million).

Conclusions

UVV was associated with significant reductions in the use of antibiotics and antivirals and their associated costs in the US. Higher vaccination coverage was associated with lower use and costs of antibiotics and antivirals for varicella management.

Immunological characteristics of MAV/06 strain of varicella-zoster virus vaccine in an animal model

BACKGROUND

Varicella-zoster virus (VZV) is a pathogen that causes chickenpox and shingles in humans. Different types of the varicella vaccines derived from the Oka and MAV/06 strains are commercially available worldwide. Although the MAV/06 vaccine was introduced in 1990s, little was known about immunological characteristics.

RESULTS

Here, we evaluated B and T cell immune response in animals inoculated with the Oka and MAV/06 vaccines as well as a new formulation of the MAV/06 vaccine. A variety of test methods were applied to evaluate T and B cell immune response. Plaque reduction neutralization test (PRNT) and fluorescent antibody to membrane antigen (FAMA) assay were conducted to measure the MAV/06 vaccine-induced antibody activity against various VZVs. Glycoprotein enzyme-linked immunosorbent assay (gpELISA) was used to compare the degree of the antibody responses induced by the two available commercial VZV vaccines and the MAV/06 vaccine. Interferon-gamma enzyme-linked immunosorbent spot (IFN-γ ELISpot) assays and cytokine bead array (CBA) assays were conducted to investigate T cell immune responses. Antibodies induced by MAV/06 vaccination showed immunogenicity against a variety of varicella-zoster virus and cross-reactivity among the virus clades.

CONCLUSIONS

It is indicating the similarity of the antibody responses induced by commercial varicella vaccines and the MAV/06 vaccine. Moreover, VZV-specific T cell immune response from MAV/06 vaccination was increased via Th1 cell response. MAV/06 varicella vaccine induced both humoral and cellular immune response via Th1 cell mediated response.

Analysis of Immunity against Measles, Mumps, Rubella, and Varicella Zoster in Adult Recipients of Allogeneic Hematopoietic Stem Cell Transplantation: A Single-Center Experience

Vaccine-preventable disease (VPD) infections are more severe in immunocompromised hosts. Vaccination against measles, mumps, rubella, and varicella zoster (VZV) (MMRV) is therefore recommended for hematopoietic stem cell transplantation (HCT) recipients. However, studies on adult HCT recipients with VPD infections are limited. At our institution, we have systematically conducted serological MMRV tests as a part of check-up examinations during long-term follow-up (LTFU) after HCT since 2015. This retrospective study aimed to evaluate changes in the serostatus between before and 2 years after allogeneic HCT. Among 161 patients, the pre-transplant seropositivity was 82.7% for measles, 86.8% for mumps, 84.2% for rubella, and 94.3% for VZV. Among 56 patients who underwent LTFU including serological MMRV tests at 2 years after HCT, the percentages maintaining seroprotective antibody levels for measles, mumps, rubella and VZV were 71.5% (40/56), 51.8% (29/56), 48.2% (27/56), and 60.7% (34/56), respectively. Vaccination was recommended for 22 patients, and 12 were vaccinated. Among the 12 vaccinated patients, rates of seroconversion were examined in 2-6 patients for each of the four viruses. They were 100% (3/3) for measles, 33.3% (1/3) for mumps, 50% (3/6) for rubella, and 0% (0/2) for VZV. Further studies are warranted to clarify the effect of vaccination in adult HCT recipients.

Economic Evaluation of Universal Varicella Vaccination in Mexico

BACKGROUND

Universal varicella vaccination has proven to be cost-effective (CE) in countries where implemented. However, this has not been evaluated for Mexico.

METHODS

The yearly disease burden (varicella cases/deaths, outpatient visits, and hospitalizations) was derived from Mexican seroprevalence data adjusted to the 2020 population. The yearly economic burden was calculated by combining disease with Mexican unit cost data from both health care and societal perspectives. Four different vaccination strategies were evaluated: (1) 1 dose of varicella vaccine at 1 year old; (2) 2 doses at 1 and 6 years; (3) 1 dose of varicella vaccine at 1 year, and quadrivalent measles-mumps-rubella-varicella vaccine at 6 years; (4) 2 doses of measles-mumps-rubella-varicella vaccine at 1 and 6 years. We developed an economic model for each vaccination strategy where 20 consecutive birth cohorts were simulated. Vaccination impact (number of avoided cases/deaths) was evaluated for a 20-year follow-up period based on vaccine effectiveness (87% and 97.4% for 1 and 2 doses), and assuming a 95% coverage. We estimated annual costs saved, incremental cost-effectiveness ratio, and costs per life year gained.

RESULTS

Avoided cases during the 20-year follow-up with 1, and 2 doses were 20,570,722 and 23,029,751, respectively. Strategies 1 and 2 were found to be cost saving, and strategy 3 to be CE. Strategy 4 was not CE. Strategies 1 and 2 would allow saving annually $53.16 and $34.41 million USD, respectively, to the Mexican society.

CONCLUSIONS

Universal varicella vaccination, using 1 dose or 2 doses, would result in a cost-beneficial and CE public health intervention in Mexico.

Rational Design of a Skin- and Neuro-Attenuated Live Varicella Vaccine: A Review and Future Perspectives

Primary varicella-zoster virus (VZV) infection causes varicella, which remains a prominent public health concern in children. Current varicella vaccines adopt the live-attenuated Oka strain, vOka, which retains the ability to infect neurons, establish latency and reactivate, leading to vaccine-associated zoster in some vaccinees. Therefore, it is necessary to develop a safer next-generation varicella vaccine to help reduce vaccine hesitancy. This paper reviews the discovery and identification of the skin- and neuro-tropic factor, the open reading frame 7 (ORF7) of VZV, as well as the development of a skin- and neuro-attenuated live varicella vaccine comprising an ORF7-deficient mutant, v7D. This work could provide insights into the research of novel virus vaccines based on functional genomics and reverse genetics.

[Varicella-zoster virus (VZV) acute retinal necrosis and recombinant zoster vaccine]

Varicella zoster virus (VZV) is responsible for chickenpox. Like all herpes viruses, after primary infection it enters into latency and can be reactivated afterwards. Many forms of symptomatic reactivation of VZV exist including acute retinal necrosis (ARN), an ophthalmic emergency which can lead to blindness. ARN is treated starting with high-dose intravenous acyclovir then with oral valaciclovir for a total duration of up to 3 months. Symptomatic reactivations of VZV are public health issues. The new Swiss 2022 vaccination plan includes the recombinant vaccine Shingrix. It effectively prevents VZV symptomatic reactivations even in elderly and immuno suppressed patients.

Effect of Routine Varicella Immunization on the Epidemiology and Immunogenicity of Varicella and Shingles

Varicella-zoster virus (VZV) causes varicella as a primary infection and remains latent in the ganglia until it becomes reactivated to cause herpes zoster. Individuals with varicella develop adaptive humoral and cell-mediated immunity. Compromised cell-mediated immunity is thought to contribute to the development of herpes zoster. Recent evidence suggests that changes in the epidemiology of varicella have affected the epidemiology of herpes zoster. The incidence of herpes zoster is higher in older adults; thus, the herpes zoster vaccine is recommended for older adults. However, the incidence of herpes zoster is expected to rise among younger individuals; hence, vaccination with the varicella vaccine should also be considered in younger adults. In order to determine the need for vaccination in different populations, it is important to establish methods to accurately assess the activity of cell-mediated immunity and humoral immunity.

[Prospective observation of breakthrough cases and analysis of antibody dynamic changes after two doses of varicella]

Objective: To investigate the breakthrough rate and antibody level of children vaccinated two doses varicella vaccine in Tianjin city, and to compare them with those vaccinated one dose. Methods: A total of 1 112 children who were vaccinated two doses varicella vaccine were selected as the experimental group. According to the same street and township, children who had received only one dose within one year of age difference, and whose first injection time was less than one month from the first dose of varicella vaccine in the experimental group were selected as the control group. A three-year prospective observation was conducted on the incidence of varicella in the two groups. 108 pairs of children in the two groups were selected to collect antivaricella serum in the first to third year. The rate of breakthrough cases, antibody level and antibody positive rate were compared by χ² test, t-test and variance analysis between and within the two groups in three years. Results: The cumulative breakthrough rate of the experimental group was 0.54%(6/1 112), which was lower than that of the control group 3.96% (44/1 112, χ²=29.544, P<0.001). The GMC level of antibody in the experimental group decreased year by year (F=18.291, P<0.001), and the GMC level in the control group also decreased year by year (F=91.383, P<0.001). There was significant difference in GMC level between the two groups (P<0.001). The difference of antibody positive rate in the experimental group was statistically significant in three years (χ²=11.107, P<0.01), there was significant difference in the positive rate between the first year and third year (P<0.01), there was no significant difference in the positive rate of the control group in three years (χ²=3.351, P>0.05). The positive rate of the experimental group was higher than that of the control group (P<0.001). Conclusion: Two doses varicella vaccine can significantly improve the antibody level and positive rate, but it still shows a downward trend with the extension of time. It is necessary to consider strengthening immunization according to the actual situation.