Impact of universal vaccination on the epidemiology of varicella in Veneto, Italy

Evaluating the Impact of Moderate and Severe Varicella Infections on Danish Children Under 18 Years Old: A Comprehensive Analysis From 2015 to 2023

BACKGROUND

Varicella (chickenpox) caused by varicella-zoster virus (VZV) is a highly contagious pediatric disease. While it typically manifests as a mild disease, complications leading to hospitalization are not uncommon. Knowing the current disease burden, seasonality and risk groups is pivotal for evidence-based decisions on the introduction of a varicella vaccine.

METHODS

Using the Danish National Patient Register and medical helpline records from the Capital Region, we estimated the burden of VZV infections among children younger than 18 years in Denmark from 2015 to June 2023.

RESULTS

We identified 14,443 cases with annual incidence rates of 325/100,000 children for mild-to-moderate varicella cases (helpline calls), 35/100,000 for moderate-to-severe cases (outpatients) and 10/100,000 for severe cases (hospitalized). Mild cases were most prevalent in children 1-4 years old, while moderate-to-severe cases were most prevalent among infants <1 year old. Among hospitalized cases, 23.2% had underlying diseases and 47.3% experienced complications. In April 2022, rapid surge in all types of VZV cases occurred, where admissions surpassed the prepandemic level.

CONCLUSION

This study documents that varicella is highly prevalent among Danish young children. Mild-to-moderately severe cases strain healthcare, causing increased helpline calls and posing a persistent hospitalization risk, especially for infants and children with underlying conditions.

Public health impact and return on investment of the pediatric National Immunization Program in Italy

OBJECTIVES

We conducted a cost-benefit analysis of the pediatric National Immunization Program (NIP) in Italy.

METHODS

An economic model evaluated the benefit-cost ratio (BCR) of the Italian pediatric NIP, including 10 pathogens for mandatory vaccines and 4 pathogens for recommended vaccines for children aged 0-10 years from the healthcare-sector and societal perspectives. Separate decision trees were used to model each vaccine-preventable disease (VPD). The 2020 birth cohort (n = 420,084) was followed over their lifetime; the model projected and compared discounted disease cases, life-years, quality-adjusted life-years (QALYs), and costs (2021 euros) with and without immunization (based on current and pre - vaccine era disease incidence estimates, respectively).

RESULTS

The pediatric NIP was estimated to prevent 1.8 million cases of VPDs and 3,330 deaths, resulting in 45,900 fewer life-years lost and 57,000 fewer QALYs lost. Vaccination costs of €285 million were offset by disease cost savings of €1.6 billion, resulting in a BCR of 5.6 from a societal perspective (BCR = 1.7 from a healthcare-sector perspective). When QALYs gained were valued, the BCR increased to 15.6.

CONCLUSIONS

The benefits of the Italian pediatric NIP, including averted disease-related morbidity, mortality, and associated costs, highlight the value of continued investment in pediatric immunization.

A changing landscape: Tracking and analysis of the international HDV epidemiology 1999-2020

The international epidemiology of Hepatitis Delta Virus (HDV) is challenging to accurately estimate due to limited active surveillance for this rare infectious disease. Prior HDV epidemiological studies have relied on meta-analysis of aggregated and static datasets. These limitations restrict the capacity to actively detect low-level and/or geographically dispersed changes in the incidence of HDV diagnoses. This study was designed to provide a resource to track and analyze the international HDV epidemiology. Datasets analyzed collectively consisted of >700,000 HBV and >9,000 HDV reported cases ranging between 1999-2020. Datasets mined from government publications were identified for Argentina, Australia, Austria, Brazil, Bulgaria, Canada, Finland, Germany, Macao, Netherlands, New Zealand, Norway, Sweden, Taiwan, Thailand, United Kingdom, and United States. Time series analyses, including Mann-Kendall (MK) trend test, Bayesian Information Criterion (BIC), and hierarchal clustering, were performed to characterize trends in the HDV timelines. An aggregated prevalence of 2,560 HDV/HBV100,000 cases (95% CI 180-4940) or 2.56% HDV/HBV cases was identified, ranging from 0.26% in Canada to 20% in the United States. Structural breaks in the timeline of HDV incidence were identified in 2002, 2012, and 2017, with a significant increase occurring between 2013-2017. Significant increasing trends in reported HDV and HBV cases were observed in 47% and 24% of datasets, respectively. Analyses of the HDV incidence timeline identified four distinct temporal clusters, including Cluster I (Macao, Taiwan), Cluster II (Argentina, Brazil, Germany, Thailand), Cluster III (Bulgaria, Netherlands, New Zealand, United Kingdom, United States) and Cluster IV (Australia, Austria, Canada, Finland, Norway, Sweden). Tracking of HDV and HBV cases on an international scale is essential in defining the global impact of viral hepatitis. Significant disruptions of HDV and HBV epidemiology have been identified. Increased surveillance of HDV is warranted to further define the etiology of the recent breakpoints in the international HDV incidence.

Vaccines for measles, mumps, rubella, and varicella in children

BACKGROUND

Measles, mumps, rubella, and varicella (chickenpox) are serious diseases that can lead to serious complications, disability, and death. However, public debate over the safety of the trivalent MMR vaccine and the resultant drop in vaccination coverage in several countries persists, despite its almost universal use and accepted effectiveness. This is an update of a review published in 2005 and updated in 2012.

OBJECTIVES

To assess the effectiveness, safety, and long- and short-term adverse effects associated with the trivalent vaccine, containing measles, rubella, mumps strains (MMR), or concurrent administration of MMR vaccine and varicella vaccine (MMR+V), or tetravalent vaccine containing measles, rubella, mumps, and varicella strains (MMRV), given to children aged up to 15 years.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2019, Issue 5), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to 2 May 2019), Embase (1974 to 2 May 2019), the WHO International Clinical Trials Registry Platform (2 May 2019), and ClinicalTrials.gov (2 May 2019).

SELECTION CRITERIA

We included randomised controlled trials (RCTs), controlled clinical trials (CCTs), prospective and retrospective cohort studies (PCS/RCS), case-control studies (CCS), interrupted time-series (ITS) studies, case cross-over (CCO) studies, case-only ecological method (COEM) studies, self-controlled case series (SCCS) studies, person-time cohort (PTC) studies, and case-coverage design/screening methods (CCD/SM) studies, assessing any combined MMR or MMRV / MMR+V vaccine given in any dose, preparation or time schedule compared with no intervention or placebo, on healthy children up to 15 years of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the methodological quality of the included studies. We grouped studies for quantitative analysis according to study design, vaccine type (MMR, MMRV, MMR+V), virus strain, and study settings. Outcomes of interest were cases of measles, mumps, rubella, and varicella, and harms. Certainty of evidence of was rated using GRADE.

MAIN RESULTS

We included 138 studies (23,480,668 participants). Fifty-one studies (10,248,159 children) assessed vaccine effectiveness and 87 studies (13,232,509 children) assessed the association between vaccines and a variety of harms. We included 74 new studies to this 2019 version of the review. Effectiveness Vaccine effectiveness in preventing measles was 95% after one dose (relative risk (RR) 0.05, 95% CI 0.02 to 0.13; 7 cohort studies; 12,039 children; moderate certainty evidence) and 96% after two doses (RR 0.04, 95% CI 0.01 to 0.28; 5 cohort studies; 21,604 children; moderate certainty evidence). The effectiveness in preventing cases among household contacts or preventing transmission to others the children were in contact with after one dose was 81% (RR 0.19, 95% CI 0.04 to 0.89; 3 cohort studies; 151 children; low certainty evidence), after two doses 85% (RR 0.15, 95% CI 0.03 to 0.75; 3 cohort studies; 378 children; low certainty evidence), and after three doses was 96% (RR 0.04, 95% CI 0.01 to 0.23; 2 cohort studies; 151 children; low certainty evidence). The effectiveness (at least one dose) in preventing measles after exposure (post-exposure prophylaxis) was 74% (RR 0.26, 95% CI 0.14 to 0.50; 2 cohort studies; 283 children; low certainty evidence). The effectiveness of Jeryl Lynn containing MMR vaccine in preventing mumps was 72% after one dose (RR 0.24, 95% CI 0.08 to 0.76; 6 cohort studies; 9915 children; moderate certainty evidence), 86% after two doses (RR 0.12, 95% CI 0.04 to 0.35; 5 cohort studies; 7792 children; moderate certainty evidence). Effectiveness in preventing cases among household contacts was 74% (RR 0.26, 95% CI 0.13 to 0.49; 3 cohort studies; 1036 children; moderate certainty evidence).  Vaccine effectiveness against rubella, using a vaccine with the BRD2 strain which is only used in China, is 89% (RR 0.11, 95% CI 0.03 to 0.42; 1 cohort study; 1621 children; moderate certainty evidence).  Vaccine effectiveness against varicella (any severity) after two doses in children aged 11 to 22 months is 95% in a 10 years follow-up (rate ratio (rr) 0.05, 95% CI 0.03 to 0.08; 1 RCT; 2279 children; high certainty evidence). Safety There is evidence supporting an association between aseptic meningitis and MMR vaccines containing Urabe and Leningrad-Zagreb mumps strains, but no evidence supporting this association for MMR vaccines containing Jeryl Lynn mumps strains (rr 1.30, 95% CI 0.66 to 2.56; low certainty evidence). The analyses provide evidence supporting an association between MMR/MMR+V/MMRV vaccines (Jeryl Lynn strain) and febrile seizures. Febrile seizures normally occur in 2% to 4% of healthy children at least once before the age of 5. The attributable risk febrile seizures vaccine-induced is estimated to be from 1 per 1700 to 1 per 1150 administered doses. The analyses provide evidence supporting an association between MMR vaccination and idiopathic thrombocytopaenic purpura (ITP). However, the risk of ITP after vaccination is smaller than after natural infection with these viruses. Natural infection of ITP occur in 5 cases per 100,000 (1 case per 20,000) per year. The attributable risk is estimated about 1 case of ITP per 40,000 administered MMR doses. There is no evidence of an association between MMR immunisation and encephalitis or encephalopathy (rate ratio 0.90, 95% CI 0.50 to 1.61; 2 observational studies; 1,071,088 children; low certainty evidence), and autistic spectrum disorders (rate ratio 0.93, 95% CI 0.85 to 1.01; 2 observational studies; 1,194,764 children; moderate certainty). There is insufficient evidence to determine the association between MMR immunisation and inflammatory bowel disease (odds ratio 1.42, 95% CI 0.93 to 2.16; 3 observational studies; 409 cases and 1416 controls; moderate certainty evidence). Additionally, there is no evidence supporting an association between MMR immunisation and cognitive delay, type 1 diabetes, asthma, dermatitis/eczema, hay fever, leukaemia, multiple sclerosis, gait disturbance, and bacterial or viral infections.  AUTHORS' CONCLUSIONS: Existing evidence on the safety and effectiveness of MMR/MMRV vaccines support their use for mass immunisation. Campaigns aimed at global eradication should assess epidemiological and socioeconomic situations of the countries as well as the capacity to achieve high vaccination coverage. More evidence is needed to assess whether the protective effect of MMR/MMRV could wane with time since immunisation.

Varicella Admissions in Children and Adolescents in Portugal: 2000-2015

OBJECTIVES

Varicella is a common, usually benign, and autolimited disease in children but can lead to severe complications and hospitalization. With this study, we aim to analyze all varicella hospitalizations to provide epidemiological information to help outline preventive policies.

METHODS

We assessed all varicella hospitalizations in children aged 0 to 17 years, from 2000 to 2015, in mainland, public Portuguese hospitals using a Portuguese administrative database. Seasonality, geographic distribution, severity, complications, risk factors, use of diagnostic and treatment procedures and hospitalization costs were analyzed.

RESULTS

A total of 5120 hospitalizations were registered, with an annual rate of 17.3 hospitalizations per 100 000 inhabitants. A higher number of hospitalizations occurred during the summer period and in Southern regions. The median length of stay was of 4 days (interquartile range: 3.0-7.0). We found a high rate of severe complications, mostly dermatologic (19.6%), neurologic (6.0%), and respiratory (5.1%). Of the total number of patients, 0.8% were immunocompromised and 0.1% were pregnant. Total direct hospitalization costs during the 16-year period were estimated to be 7 110 719€ (8 603 970 USD), with a mean annual cost of 444 419.92€ (537 748.10 USD).

CONCULSIONS

This is the first national study in which useful epidemiological data to evaluate the burden and impact of varicella in Portugal is provided.

Cross-Sectional Study of Varicella Zoster Virus Immunity in Healthy Korean Children Assessed by Glycoprotein Enzyme-Linked Immunosorbent Assay and Fluorescent Antibody to Membrane Antigen Test

The prevalence of varicella is especially high among children in the age group of 4-6 years in South Korea, regardless of vaccination. We investigated the immune status of healthy children enrolled in day-care centers and compared pre- and post-vaccination immunity. Antibody titers were measured using a glycoprotein enzyme-linked immunosorbent assay (gpEIA) kit, and the seroconversion rate was assessed using a fluorescent antibody to membrane antigen (FAMA) test. Among 541 vaccinated children, 109 (20.1%) had breakthrough varicella. However, 13 (72.2%) of the 18 unvaccinated children had a history of varicella. The gpEIA geometric mean titers (GMTs) of pre- and 5 weeks post-vaccination in 1-year-old children were 14.7 and 72 mIU/mL, respectively, and the FAMA seroconversion rate was 91.1%. The gpEIA GMTs of 2-, 3-, 4-, 5-, and 6-year-old children were 104.1, 133.8, 223.5, 364.1, and 353.0 mIU/mL, respectively. Even though the gpEIA GMT increased with age, the pattern of gpEIA titer distribution in 4- to 6-year-old vaccinees without varicella history represented both waning immunity and natural boosting immunity. These results suggest that some vaccinees are vulnerable to varicella infection. Therefore, it is necessary to consider a two-dose varicella vaccine regimen in South Korea.

Varicella seroepidemiology and immunization in a cohort of future healthcare workers in the pre-vaccination era

OBJECTIVES

The goal of this study was to establish the seroprevalence of positive antibodies against varicella and compliance with varicella vaccination in the pre-vaccination era.

METHODS

A cohort of 10 683 Italian students from Padua University Medical School (from 2004 to 2019) were enrolled and classified as unvaccinated, vaccinated once, or vaccinated twice against varicella, according to their vaccination certificate. The antibody titre was measured and the seroprevalence of positive subjects was determined. Subjects with negative or equivocal antibodies were invited for vaccination, and then the antibody titre was retested.

RESULTS

Unvaccinated students were mostly seropositive (95.6%), compared with vaccinated students who were less seropositive (68.0% after one dose and 78.6% after two doses) and had significantly lower antibody titres (p < 0.0001). The post-test vaccination had a positive response rate of 85.4%: 67.4% after one dose and 91.4% after two doses.

CONCLUSIONS

In the pre-vaccination era, only 3.3% of future healthcare workers were vaccinated against varicella (1.1% once and 2.2% twice). Vaccination or revaccination of negative and equivocal individuals could reduce the number of susceptible people. Implementation of varicella vaccine (two doses) in healthcare workers is of primary importance to reduce the risk of transmission.

Vaccines for measles, mumps, rubella, and varicella in children

BACKGROUND

Measles, mumps, rubella, and varicella (chickenpox) are serious diseases that can lead to serious complications, disability, and death. However, public debate over the safety of the trivalent MMR vaccine and the resultant drop in vaccination coverage in several countries persists, despite its almost universal use and accepted effectiveness. This is an update of a review published in 2005 and updated in 2012.

OBJECTIVES

To assess the effectiveness, safety, and long- and short-term adverse effects associated with the trivalent vaccine, containing measles, rubella, mumps strains (MMR), or concurrent administration of MMR vaccine and varicella vaccine (MMR+V), or tetravalent vaccine containing measles, rubella, mumps, and varicella strains (MMRV), given to children aged up to 15 years.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2019, Issue 5), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to 2 May 2019), Embase (1974 to 2 May 2019), the WHO International Clinical Trials Registry Platform (2 May 2019), and ClinicalTrials.gov (2 May 2019).

SELECTION CRITERIA

We included randomised controlled trials (RCTs), controlled clinical trials (CCTs), prospective and retrospective cohort studies (PCS/RCS), case-control studies (CCS), interrupted time-series (ITS) studies, case cross-over (CCO) studies, case-only ecological method (COEM) studies, self-controlled case series (SCCS) studies, person-time cohort (PTC) studies, and case-coverage design/screening methods (CCD/SM) studies, assessing any combined MMR or MMRV / MMR+V vaccine given in any dose, preparation or time schedule compared with no intervention or placebo, on healthy children up to 15 years of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the methodological quality of the included studies. We grouped studies for quantitative analysis according to study design, vaccine type (MMR, MMRV, MMR+V), virus strain, and study settings. Outcomes of interest were cases of measles, mumps, rubella, and varicella, and harms. Certainty of evidence of was rated using GRADE.

MAIN RESULTS

We included 138 studies (23,480,668 participants). Fifty-one studies (10,248,159 children) assessed vaccine effectiveness and 87 studies (13,232,509 children) assessed the association between vaccines and a variety of harms. We included 74 new studies to this 2019 version of the review. Effectiveness Vaccine effectiveness in preventing measles was 95% after one dose (relative risk (RR) 0.05, 95% CI 0.02 to 0.13; 7 cohort studies; 12,039 children; moderate certainty evidence) and 96% after two doses (RR 0.04, 95% CI 0.01 to 0.28; 5 cohort studies; 21,604 children; moderate certainty evidence). The effectiveness in preventing cases among household contacts or preventing transmission to others the children were in contact with after one dose was 81% (RR 0.19, 95% CI 0.04 to 0.89; 3 cohort studies; 151 children; low certainty evidence), after two doses 85% (RR 0.15, 95% CI 0.03 to 0.75; 3 cohort studies; 378 children; low certainty evidence), and after three doses was 96% (RR 0.04, 95% CI 0.01 to 0.23; 2 cohort studies; 151 children; low certainty evidence). The effectiveness (at least one dose) in preventing measles after exposure (post-exposure prophylaxis) was 74% (RR 0.26, 95% CI 0.14 to 0.50; 2 cohort studies; 283 children; low certainty evidence). The effectiveness of Jeryl Lynn containing MMR vaccine in preventing mumps was 72% after one dose (RR 0.24, 95% CI 0.08 to 0.76; 6 cohort studies; 9915 children; moderate certainty evidence), 86% after two doses (RR 0.12, 95% CI 0.04 to 0.35; 5 cohort studies; 7792 children; moderate certainty evidence). Effectiveness in preventing cases among household contacts was 74% (RR 0.26, 95% CI 0.13 to 0.49; 3 cohort studies; 1036 children; moderate certainty evidence). Vaccine effectiveness against rubella is 89% (RR 0.11, 95% CI 0.03 to 0.42; 1 cohort study; 1621 children; moderate certainty evidence). Vaccine effectiveness against varicella (any severity) after two doses in children aged 11 to 22 months is 95% in a 10 years follow-up (rate ratio (rr) 0.05, 95% CI 0.03 to 0.08; 1 RCT; 2279 children; high certainty evidence). Safety There is evidence supporting an association between aseptic meningitis and MMR vaccines containing Urabe and Leningrad-Zagreb mumps strains, but no evidence supporting this association for MMR vaccines containing Jeryl Lynn mumps strains (rr 1.30, 95% CI 0.66 to 2.56; low certainty evidence). The analyses provide evidence supporting an association between MMR/MMR+V/MMRV vaccines (Jeryl Lynn strain) and febrile seizures. Febrile seizures normally occur in 2% to 4% of healthy children at least once before the age of 5. The attributable risk febrile seizures vaccine-induced is estimated to be from 1 per 1700 to 1 per 1150 administered doses. The analyses provide evidence supporting an association between MMR vaccination and idiopathic thrombocytopaenic purpura (ITP). However, the risk of ITP after vaccination is smaller than after natural infection with these viruses. Natural infection of ITP occur in 5 cases per 100,000 (1 case per 20,000) per year. The attributable risk is estimated about 1 case of ITP per 40,000 administered MMR doses. There is no evidence of an association between MMR immunisation and encephalitis or encephalopathy (rate ratio 0.90, 95% CI 0.50 to 1.61; 2 observational studies; 1,071,088 children; low certainty evidence), and autistic spectrum disorders (rate ratio 0.93, 95% CI 0.85 to 1.01; 2 observational studies; 1,194,764 children; moderate certainty). There is insufficient evidence to determine the association between MMR immunisation and inflammatory bowel disease (odds ratio 1.42, 95% CI 0.93 to 2.16; 3 observational studies; 409 cases and 1416 controls; moderate certainty evidence). Additionally, there is no evidence supporting an association between MMR immunisation and cognitive delay, type 1 diabetes, asthma, dermatitis/eczema, hay fever, leukaemia, multiple sclerosis, gait disturbance, and bacterial or viral infections.

AUTHORS' CONCLUSIONS

Existing evidence on the safety and effectiveness of MMR/MMRV vaccines support their use for mass immunisation. Campaigns aimed at global eradication should assess epidemiological and socioeconomic situations of the countries as well as the capacity to achieve high vaccination coverage. More evidence is needed to assess whether the protective effect of MMR/MMRV could wane with time since immunisation.

Global impact of varicella vaccination programs

Although varicella is usually a mild and self-limited disease, complications can occur. In 1998, the World Health Organization recommended varicella vaccination for countries where the disease has a significant public health burden. Nonetheless, concerns about a shift in the disease to older groups, an increase in herpes zoster in the elderly and cost-effectiveness led many countries to postpone universal varicella vaccine introduction. In this review, we summarize the accumulating evidence, available mostly from high and middle-income countries supporting a high impact of universal vaccination in reductions of the incidence of the disease and hospitalizations and its cost-effectiveness. We have also observed the effect of herd immunity and noted that there is no definitive and consistent association between vaccination and the increase in herpes zoster incidence in the elderly.

Gene Therapy for Adenosine Deaminase Deficiency: A Comprehensive Evaluation of Short- and Medium-Term Safety

Loss of adenosine deaminase activity leads to severe combined immunodeficiency (ADA-SCID); production and function of T, B, and natural killer (NK) cells are impaired. Gene therapy (GT) with an autologous CD34⁺-enriched cell fraction that contains CD34⁺ cells transduced with a retroviral vector encoding the human ADA cDNA sequence leads to immune reconstitution in most patients. Here, we report short- and medium-term safety analyses from 18 patients enrolled as part of single-arm, open-label studies or compassionate use programs. Survival was 100% with a median of 6.9 years follow-up (range, 2.3 to 13.4 years). Adverse events were mostly grade 1 or grade 2 and were reported by all 18 patients following GT. Thirty-nine serious adverse events (SAEs) were reported by 15 of 18 patients; no SAEs were considered related to GT. The most common adverse events reported post-GT include upper respiratory tract infection, gastroenteritis, rhinitis, bronchitis, oral candidiasis, cough, neutropenia, diarrhea, and pyrexia. Incidence rates for all of these events were highest during pre-treatment, treatment, and/or 3-month follow-up and then declined over medium-term follow-up. GT did not impact the incidence of neurologic/hearing impairments. No event indicative of leukemic transformation was reported.

Early impact of universal varicella vaccination on childhood varicella and herpes zoster hospitalizations in Brazil

INTRODUCTION

The Brazilian childhood National Immunization Program (NIP) introduced live and attenuated varicella vaccination in a single dose, combined as tetraviral vaccine, at 15 months of age in the whole country, during September to December of 2013. The aim of this study was to report trends in incidence of childhood hospital admissions related to varicella and zoster in Brazil from 2003 to 2016, including the first three years after vaccine introduction.

METHODS

The number and incidence of hospital admission in patients aged less than 20 years in Brazilian public health system with an admission diagnosis of varicella and zoster from 2003 to 2016 were analyzed and pre (2003-2013) and post-vaccination periods (2014-2016) were compared. The data were obtained from DATASUS, a Brazilian government's open-access public health database system, and analyzed adjusting for secular trend and seasonality if a statistically significant change was found.

RESULTS

During the study period, 69,791 admissions due to varicella and herpes zoster occurred in the children younger than 20 years. After adjusting for seasonality, the incidence of hospitalizations decreased from 27.33 to 14.33 per 100000 per year, which corresponds to a reduction of 47.6% (95% confidence interval 18.19-77.04%, p < 0.001) in the vaccinated age group (1-4 years) in 2014-2016 compared to pre-vaccination period. The changes were not significant in the unvaccinated age groups.

CONCLUSION

The hospitalizations due to varicella and herpes zoster were decreased by half early after the introduction of a single dose of tetraviral vaccine in NIP in the vaccinated children. Further studies may assess duration and intensity of this effect, as well as the indirect effect in the unvaccinated age groups.

Safety and immunogenicity of Bio Pox™, a live varicella vaccine (Oka strain) in Indian children: A comparative multicentric, randomized phase II/III clinical trial

Varicella or chickenpox is a highly contagious disease with a high secondary attack rate. Almost 30% of Indian adolescents lack protective antibodies against varicella, emphasizing the need of routine varicella immunization. The Oka VZV is a well-established, safe and efficacious vaccine strain that is highly immunogenic and produces lifelong protective immunity. The present multicentric, open label, randomized, controlled Phase II/III study, compared the Bio Pox™ (indigenous investigational vaccine) with a licensed vaccine, Varivax™ [a][a] Please note that this article refers to the product named VARIVAX as manufactured by Changchun Keygen Biological Products Ltd., China and marketed in India by VHB Life Sciences Limited, Mumbai, and not the product VARIVAX® owned by Merck Sharp & Dohme Corp., Rahway, New Jersey, USA. Merck Sharp & Dohme Corp. have asked us to make clear that the product manufactured by Changchun Keygen Biological Products Ltd. is unrelated to and is not sponsored, endorsed or otherwise authorised by Merck Sharp & Dohme Corp. , for its safety and immunogenicity profile in 252 healthy subjects in the age group of 1-12 y (cohort I: 6-12 years, II:1-6 years) in 3 tertiary medical institutions. Antibodies were measured by VZV Glycoprotein Enzyme Linked Immunoassay (IgG ELISA) kit. Seroconversion percentage in children having pre-vaccination anti VZV IgG titer <10 mIU/mL (< 5 gp ELISA units/mL) were 80% for Bio Pox™ and 77% for Varivax™ (p = 0.692). The seroconversion rate in the group receiving Bio Pox™ was non-inferior to the group that received Varivax™. There were mild local reactions for both the vaccines; none of the patient had fever or required hospitalization or medication. The Bio Pox™ was found to be safe and immunogenic in children against VZV infection.

A national register-based study of paediatric varicella hospitalizations in Denmark 2010–2016

Varicella, usually a mild disease of childhood, can also cause complications and hospitalization. Universal varicella immunization is implemented in several countries worldwide, but not in Denmark. Taking advantage of unique national registers, we aimed to estimate the incidence of paediatric varicella hospitalizations and assess determinants for hospitalization. For this purpose, we designed a nationwide, retrospective register study of paediatric varicella hospitalizations and applied a case–cohort design and logistic regression analysis comparing hospitalized varicella patients to a sample of the entire paediatric population in Denmark. Varicella patients were identified in The Danish National Patient Register and referents were randomly selected from the Danish Civil Registration System. The incidence of paediatric varicella admissions was 11/100 000 children 0–18 years of age/year. Of admitted children 67·1% had complications and 30·0% had underlying disease. All categories of underlying disease significantly increased the odds of hospitalization as well as male gender and not having been born in Denmark. In conclusion, we found a considerable burden of paediatric varicella disease in Danish hospitals, of similar magnitude as in other European countries comparable to Denmark. With this study we have provided epidemiological data needed for considering implementation of varicella vaccine in Denmark.

Varicella vaccination - the global experience

INTRODUCTION

Varicella, although a frequently benign childhood disease, nevertheless represents a considerable health burden. WHO recommends including varicella vaccines in universal routine vaccination programs, and maintaining coverage >80%. Many countries have successfully introduced varicella vaccination and have benefited from lower disease burden, but many others have not adopted the vaccine. Reasons include cost commitment for a 'mild childhood disease' or concerns that vaccination will shift varicella to older age groups or increase herpes zoster incidence. Areas covered: This literature review summarizes the effectiveness and epidemiological impact of varicella immunization programs. Expert commentary: Varicella vaccines are immunogenic with acceptable safety profiles. One and two dose schedules are highly effective against varicella and large reductions in disease incidence, particularly moderate-severe disease, have been widely reported. There is currently no evidence to suggest that the introduction of varicella vaccination results in a shift of varicella disease burden to older age groups. Although epidemiological studies have shown an increased incidence of herpes zoster since the vaccines were launched, there are many other contributing factors, and indeed, this secular trend was evident before their introduction. In conclusion, varicella vaccination easily fits into existing immunization programs and significantly reduces the often underestimated burden of varicella.

Preparing to introduce the varicella vaccine into the Italian immunisation programme: varicella-related hospitalisations in Tuscany, 2004-2012

A universal immunisation programme against varicella in the form of the measles-mumps-rubella-varicella (MMRV) vaccine for toddlers aged 13-15 months was introduced in Tuscany in July 2008. An assessment of the impact of this programme on varicella-related hospitalisations 4 years after its introduction could further support its adoption at a national level. The hospitalisation data were analysed in two periods: pre-vaccination (2004-2007) and vaccination period (2009-2012). The high coverage of the vaccines (84% in 2012) resulted in a significant decline in notifications, from 33,114 (2004-2007) to 13,184 cases (2009-2012), and also of hospitalisations, from 584 (pre-vaccination period) to 325 (vaccination period). The hospitalisation rate was 4.1 per 100,000 (95% confidence intervals (CI): 3.4-4.7) before the introduction of vaccination, which dropped to 2.2 per 100,000 (95% CI: 1.7-2.7) in the vaccination period (hospitalisation risk ratios: 0.54; 95% CI:  0.472-0.619). The reduction was most significant in the youngest age groups. The introduction of universal vaccination has already led to a significant decline in hospitalisations due to varicella after just 4 years of implementation. Hospitalisation rates fell noticeably among younger individuals involved in the vaccination programme. The decrease in hospitalisation rate in the older age groups suggests a possible indirect protection.

The burden of chickenpox disease in Sweden

Background

Chickenpox vaccine is not included in the routine childhood vaccination programme in Sweden. The aim of this study was to estimate the baseline of national chickenpox disease burden, as comprehensive studies, required for an assessment regarding vaccine introduction, are lacking.

Methods

We used available health care registers and databases; the death register, hospitalisations register, communicable disease notifications database, Stockholm County registers on consultations in specialist and primary care, temporary parental benefit to care for a sick child, and searches on the health care system’s website.

From each data source, records regarding chickenpox were identified and extracted, either using relevant diagnosis codes (ICD-10) or key words. A descriptive analysis with regards to number of cases and incidence, severity, and seasonality, was carried out covering the time period 2007 to 2013.

Results

There were on average 333 patients hospitalised annually due to chickenpox, yielding a hospitalisation rate of 3.56/100,000 person-years. We found a slight male predominance in hospitalised cases. The highest hospitalisation rate was seen in 1 year-olds, whereas the peak in primary care consultations was in 2 year-olds. Nearly a quarter of children had parents who reported absence from work to care for them when sick with chickenpox. The average yearly death rate from chickenpox was 0.034/100,000 person-years. The duration of hospital stay increased with age. The seasonality in number of searches on the health care website corresponded well with hospitalisations and primary care consultations with peaks in spring.

Conclusions

This study shows chickenpox death and hospitalisation rates in range with other European countries without routine vaccination. Swedish children fall ill with chickenpox at a very young age.

The study provides essential input for future discussions on the introduction of routine chickenpox vaccination in Sweden.

Varicella in Europe-A review of the epidemiology and experience with vaccination

There is no consensus as regards the European varicella immunisation policy; some countries have introduced varicella vaccination in their routine childhood immunisation programs whereas others have decided against or are debating. With the aim of providing an overview of the epidemiology of varicella in Europe and addressing the different strategies and the experiences so far, we performed a review of epidemiological studies done in Europe from 2004 to 2014. Varicella is mainly a disease of childhood, but sero-epidemiological studies show regional differences in the proportion of susceptible adults. Hospitalisation due to varicella is not common, but complications and hospitalisation mainly affect previously healthy children, which underlines the importance of not dismissing varicella as a disease of little importance. The experience with universal vaccination in Europe shows that vaccination leads to a rapid reduction of disease incidence. Vaccine effectiveness is high and a protective herd effect is obtained. Experience with vaccination in Europe has not been long enough, though, to draw conclusions on benefits and drawbacks with vaccination as well as the capacity for national programs in Europe to maintain a sufficiently high coverage to prevent a change in age group distribution to older children and young adults or on the impact that varicella immunisation may have on the epidemiology of shingles.

Impact of universal vaccination against varicella in Italy

In Italy, the introduction of Universal Varicella Vaccination (UVV) has been decided but postponed, as a national programme, until 2015, when data from Regions which have already implemented it will be available. Starting from 2003, eight Italian Regions (Basilicata, Calabria, Friuli Venezia Giulia, Apulia, Sardinia, Sicily, Tuscany and Veneto) have progressively introduced UVV, in their immunization programme, with different schedules in children aged 13-15 months and 5-6 years, currently a two-dose schedule is adopted by all Regions. In June 2013, an Interregional Group on Varicella Vaccination (IGVV) has been established in order to assess the effectiveness of varicella vaccination with standardized and shared tools. The aim of this study was to evaluate the impact of varicella vaccination on the incidence and hospitalizations due to varicella and its complications in the period 2003-2012 in order to support the Italian decision makers on the future national adoption. Preliminary data showed that a general reduction of incidence and hospitalization rates was observed in the study period, resulting in relevant savings for the National Health Service. Immunization coverage with first dose at 24 months of age was high in all Regions (84%-95%) in 2012. Adverse events due to varicella vaccines were rare and without permanent sequelae. Underreporting of varicella cases and delays in the administration of the first dose of varicella vaccines were the main critical issues. In conclusion, solid evidences in support of universal UVV arise from the experiences available today in Italy.

Effectiveness of vaccination against varicella in children under 5 years in Puglia, Italy 2006-2012

In Italy, between 2003 and 2010, 8/21 Regions recommended varicella routine vaccination (URV). The National Immunization Plan (PNPV) 2012-2014 scheduled the introduction of URV nationwide in 2015, following the results achieved by the eight Regions.   Puglia adopted varicella URV in 2006. This study describes epidemiology and costs of varicella in Puglia between 2003 and 2012. One-dose Vaccine Effectiveness (VE) against varicella of any severity and severe hospitalized cases in children was also evaluated. Vaccination coverage (VC) was estimated from the regional immunization registry. Incidence and hospitalization rates were calculated from computerised surveillance system for communicable diseases and hospital discharge registry (ICD9-CM codes: 052.x), respectively. URV impact was assessed by Incidence Rate Ratios (IIRs) and Hospitalization Risk Ratios (HRRs). Hospitalization costs were also evaluated. VE was estimated using the screening method, where PPV was VC in children aged &lt;72 months and PCV was the proportion of cases vaccinated among notified or hospitalized cases, respectively. One-dose VC in children aged ≤ 24 months increased from 49% in the birth cohort 2006 to 91.1% in the cohort 2010; 2-dose VC was 64.8% and 28.8% in the 2005 and 1997 cohort, respectively. Comparing pre and post-vaccination era, incidence declined from 122.5 ×100 000 in 2003-2005 to 13.7 in 2009-2012 (IRR = 0.11, 95% CI = 0.10-0.12), hospitalization rate from 3.9 ×100 000 to 1.1 (HRR = 0.29, 95% CI = 0.21-0.4), hospitalization costs from 319 000 Euros/year to 106 000. One-dose VE against varicella of any severity and severe hospitalized disease was 98.8% and 99%, respectively. Our findings strongly support varicella URV introduction into the Italian Essential Health Interventions, as scheduled by 2015.

Varicella and herpes zoster hospitalizations before and after implementation of one-dose varicella vaccination in Australia: an ecological study

OBJECTIVE

To examine trends in varicella and herpes zoster (HZ) hospitalization following the availability and subsequent National Immunization Programme funding of one-dose varicella vaccination in Australia.

METHODS

Varicella vaccination coverage for children born between 2001 and 2009 was obtained from the Australian Childhood Immunization Register. Principal or any coded varicella or HZ hospitalizations were retrieved from the national hospital morbidity database from 1998 to 2010. Trends in hospitalization rates in different age groups and indigenous status were assessed. Incidence rate ratios (IRR) were calculated between periods before and after implementation of immunization programme funding.

FINDINGS

In the first year of the funded immunization programme, varicella vaccine coverage reached 75% in children aged 24 months and more than 80% in children aged 60 months. Compared with the pre-vaccine period, varicella hospitalization rates during the funded programme were significantly lower for age groups younger than 40 years; with the greatest reduction in children aged 18-59 months (IRR: 0.25; 95% confidence interval, CI: 0.22-0.29). Indigenous children had a higher varicella hospitalization rate compared with non-indigenous children before vaccine implementation (IRR: 1.9; 95% CI: 1.4-2.7), but afterwards reached equivalence (IRR: 1.1; 95% CI: 0.7-1.6). The age-standardized HZ hospitalization rate declined between the periods (IRR: 0.95; 95% CI: 0.92-0.97).

CONCLUSION

Rapid attainment of high coverage reduced varicella hospitalizations in the targeted age group, particularly for indigenous children, but also in non-targeted age groups, with no increase in HZ hospitalizations. This suggests high one-dose varicella vaccine coverage can have a substantial impact on severe disease.

Impact of universal two-dose vaccination on varicella epidemiology in Navarre, Spain, 2006 to 2012

In 2007 in Navarre, Spain, universal varicella vaccination with two doses of Varivax was introduced in the childhood immunisation schedule for children aged 15 months and three years. This study describes changes in the epidemiology of varicella in the period 2006 to 2012 and evaluates vaccination effectiveness using epidemiological surveillance data. The incidence of varicella in children aged 0 to 14 years decreased by 98.1%, from 50.1 cases per 1,000 inhabitants in 2006, to 1.0 per 1,000 in 2012. Children aged one to eight years were the vaccinated cohorts, and their incidence of varicella decreased by 98.5% (p<0.0001). In unvaccinated age groups, important reductions were also achieved between 2006 and 2012: 90.5% (p<0.0001) in infants under one year of age, and 89.4% (p<0.0001) in children aged nine years. In the period 2006 to 2012, the hospital admissions rate for varicella or its complications decreased by 89.0%, and in 2012, there was only one admission of a newborn with neonatal varicella. Vaccine effectiveness for at least one dose was 96.8% (95% confidence interval: 96.3-97.2%). Universal vaccination with two doses has reduced varicella circulation to minimum levels within five years and has proved highly effective.

Children Hospitalized for Varicella: Complications and Cost Burden

OBJECTIVE

To evaluate the direct medical cost of hospital admissions for patients with varicella (i.e., chickenpox) to assess the cost burden of varicella from a health care perspective for ultimate use in health economics studies in Turkey.

METHODS

Records of children hospitalized with varicella at the Bakirkoy Maternity and Children's Hospital between November of 2006 and June of 2011 were reviewed. Reasons for hospitalization, types of varicella-associated complications, and direct medical cost of hospitalization were noted. Patients with underlying risk factors were excluded. Data obtained from one hospital were used to estimate the national cost of the disease.

RESULTS

During the 4.5-year study period, 234 patients were hospitalized with varicella. Of these cases, 48 (20%) children previously ill with underlying cancers or chronic diseases were excluded from the study. Ultimately, 186 previously healthy children (age range: 14 days to 159 months, median age: 14 months) were included. The main reasons for hospitalization were complications related to varicella (79%), the most frequent of which was skin and soft tissue infections, followed by neurological complications and pneumonia. The median cost of hospitalization per patient was US $283, 50% of which was attributed to medication costs. The annual cost for varicella hospitalizations in Turkey was estimated at US $396,200.

CONCLUSIONS

A significant number of healthy children are hospitalized for varicella and associated complications. Descriptions of these complications and their related costs provide important data for cost-effectiveness studies for decisions about the inclusion of the varicella vaccine in a childhood vaccination program.

Varicella routine vaccination and the effects on varicella epidemiology - results from the Bavarian Varicella Surveillance Project (BaVariPro), 2006-2011

BACKGROUND

In 2004, routine varicella vaccination was recommended in Germany for children 11-14 months of age with one dose, and since 2009, with a second dose at 15-23 months of age. The effects on varicella epidemiology were investigated.

METHODS

Data on varicella vaccinations, cases and complications were collected from annual parent surveys (2006-2011), monthly paediatric practice surveillance (Oct 2006 - Sep 2011; five varicella seasons) and paediatric hospital databases (2005-2009) in the area of Munich (about 238,000 paediatric inhabitants); annual incidences of cases and hospitalisations were estimated.

RESULTS

Varicella vaccination coverage (1st dose) in children 18-36 months of age increased in two steps (38%, 51%, 53%, 53%, 66% and 68%); second-dose coverage reached 59% in the 2011 survey. A monthly mean of 82 (62%) practices participated; they applied a total of 50,059 first-dose and 40,541 second-dose varicella vaccinations, with preferential use of combined MMR-varicella vaccine after recommendation of two doses, and reported a total of 16,054 varicella cases <17 years of age. The mean number of cases decreased by 67% in two steps, from 6.6 (95%CI 6.1-7.0) per 1,000 patient contacts in season 2006/07 to 4.2 (95%CI 3.9-4.6) in 2007/08 and 4.0 (95%CI 3.6-4.3) in 2008/09, and further to 2.3 (95%CI 2.0-2.6) in 2009/10 and 2.2 (95%CI 1.9-2.5) in 2010/11. The decrease occurred in all paediatric age groups, indicating herd protection effects. Incidence of varicella was estimated as 78/1,000 children <17 years of age in 2006/07, and 19/1,000 in 2010/11. Vaccinated cases increased from 0.3 (95%0.2-0.3) per 1,000 patient contacts in 2006/07 to 0.4 (95%CI 0.3-0.5) until 2008/09 and decreased to 0.2 (95%CI 0.2-0.3) until 2010/11. The practices treated a total of 134 complicated cases, mainly with skin complications. The paediatric hospitals recorded a total of 178 varicella patients, including 40 (22.5%) with neurological complications and one (0.6%) fatality due to varicella pneumonia. Incidence of hospitalisations decreased from 7.6 per 100,000 children <17 years of age in 2005 to 4.3 in 2009, and from 21.0 to 4.7 in children <5 years of age.

CONCLUSIONS

Overall, the results show increasing acceptance and a strong impact of the varicella vaccination program, even with still suboptimal vaccination coverage.

Primary versus secondary failure after varicella vaccination: implications for interval between 2 doses

BACKGROUND

Two-dose varicella vaccination is recommended for optimal control of varicella in populations with high (>90%) 1-dose coverage. Optimal timing of the second dose may depend on whether breakthrough varicella results from primary vaccine failure (no protective immunity after vaccination) or secondary vaccine failure (waning protective immunity).

METHODS

Published literature (1995 to 2012) on vaccine failure after varicella vaccination cited in PubMed and other online sources was reviewed.

RESULTS

Nineteen publications detailed 21 varicella outbreaks with breakthrough varicella rates ranging from 0% to 42%; the publications showed no consistent trend between breakthrough varicella rate and time since vaccination.

CONCLUSIONS

Literature to date indicates a relatively high rate of primary vaccine failure and limited evidence of secondary vaccine failure among 1-dose varicella vaccine recipients, suggesting that a short interval between 2 doses might be preferable in countries considering implementation of universal varicella vaccination to reduce breakthrough varicella. However, any potential disruption to well-established vaccination schedules should be considered.

Cycling probe technology to quantify and discriminate between wild-type varicella-zoster virus and Oka vaccine strains

Rapid differentiation between wild-type varicella zoster virus (VZV) and Oka-vaccine (vOka) strains is important for monitoring side reactions of varicella vaccination. To develop a high-throughput molecular diagnostic method for the differentiation of wild-type VZV and vOka strains based on cycling probe technology. The primers were designed to amplify common sequences spanning a single nucleotide polymorphism (SNP) in gene 62 of VZV. DNA-RNA chimeric probes (cycling probes) were designed to detect the SNP at nucleotide 105705. The cycling probe real-time PCR assays for VZV wild-type and vOka strains specifically amplified plasmids containing target sequences that ranged between 10 and 1×10(6) copies per reaction. The inter- and intra-assay coefficients of variation were less than 5%. After initial validation studies, the clinical reliability of this method was evaluated using 38 swab samples that were collected from patients suspected of being zoster. Compared to the loop mediated isothermal amplification method, which is defined as the gold standard, cycling probe real-time PCR was highly sensitive and specific. The cycling probe real-time PCR technology is a reliable tool for differentiating between wild-type VZV and vOka strains in clinical samples.

Infectious diseases and vaccination strategies: how to protect the "unprotectable"?

Introduction. The circulation of infectious diseases puts small infants too young to be vaccinated at risk of morbidity and mortality, often requiring prolonged hospitalization. Material and Methods. We have reviewed the medical records of children not eligible for vaccination because of age, admitted to hospital for pertussis, measles, or varicella from February 1, 2010, till February 1, 2012. Results. Of the case records scrutinized, 21 were hospitalized for pertussis, 18 for measles, and 32 for varicella. Out of them, 42%, 66%, and 78% diagnosed with, respectively, pertussis, measles, and varicella had a complicated course of the disease. Discussion. To avoid infectious disease circulation, childhood immunization strategies should be adopted, such as vaccination of healthcare givers, adult household contacts, and parents planning to have, or who have had, a newborn baby.

Review of the United States universal varicella vaccination program: Herpes zoster incidence rates, cost-effectiveness, and vaccine efficacy based primarily on the Antelope Valley Varicella Active Surveillance Project data

In a cooperative agreement starting January 1995, prior to the FDA's licensure of the varicella vaccine on March 17, the Centers for Disease Control and Prevention (CDC) funded the Los Angeles Department of Health Services' Antelope Valley Varicella Active Surveillance Project (AV-VASP). Since only varicella case reports were gathered, baseline incidence data for herpes zoster (HZ) or shingles was lacking. Varicella case reports decreased 72%, from 2834 in 1995 to 836 in 2000 at which time approximately 50% of children under 10 years of age had been vaccinated. Starting in 2000, HZ surveillance was added to the project. By 2002, notable increases in HZ incidence rates were reported among both children and adults with a prior history of natural varicella. However, CDC authorities still claimed that no increase in HZ had occurred in any US surveillance site. The basic assumptions inherent to the varicella cost-benefit analysis ignored the significance of exogenous boosting caused by those shedding wild-type VZV. Also ignored was the morbidity associated with even rare serious events following varicella vaccination as well as the morbidity from increasing cases of HZ among adults. Vaccine efficacy declined below 80% in 2001. By 2006, because 20% of vaccinees were experiencing breakthrough varicella and vaccine-induced protection was waning, the CDC recommended a booster dose for children and, in 2007, a shingles vaccination was approved for adults aged 60 years and older. In the prelicensure era, 95% of adults experienced natural chickenpox (usually as children)-these cases were usually benign and resulted in long-term immunity. Varicella vaccination is less effective than the natural immunity that existed in prevaccine communities. Universal varicella vaccination has not proven to be cost-effective as increased HZ morbidity has disproportionately offset cost savings associated with reductions in varicella disease. Universal varicella vaccination has failed to provide long-term protection from VZV disease.

Clinical epidemiology of chickenpox in Iraq from 2007-2011

Varicella zoster (chickenpox) infection is an acute common disease caused by the varicella zoster virus (VZV). Children are most susceptible to infection. In non-vaccinated populations, primary infection tends to occur at a younger age. In 1998, the World Health Organization (WHO) recommended that routine childhood varicella vaccination be considered in countries where the disease is a relatively important public health and socioeconomic problem, and where high (85 to 90%) and sustained vaccine coverage can be achieved.