History Of Varicella Research Articles

Presentation Number WSOH-15 - The Association Between Seropositivity and Self-Reported History of Varicella and Measles: Can We Rely on Self-Reported History?

Presentation Number WSOH-15 - The Association Between Seropositivity and Self-Reported History of Varicella and Measles: Can We Rely on Self-Reported History?

Varicella vaccination: scientific reasons for a different strategic approach

The Italian Parliament has recently introduced 10 mandatory immunisations, including the one against varicella. For this vaccination, the obligation starts with the birth cohort of 2017, but it is offered free of charge to subjects with a negative history and not previously vaccinated. This paper presents up-to-date evidence on this issue and illustrates a number of critical arguments that may question the opportunity of this choice. Particularly, while the disease is relatively mild in children aged between 1 and 9 years, the risk of worsening its consequences is progressive with age, becoming worst in the elderly, so the vaccination of children may increase the age of the cases. Some vaccine side effects are not trivial and the duration of protection is still uncertain, as well as the cost-effectiveness of mass vaccination and its long-term effects, referring to virus reactivation and to the incidence of Herpes zoster in the general population, which could be increased and anticipated in the long run. Varicella vaccination is not included in international eradication goals and very few Europeans Countries have considered it as a public health priority. A different rational choice could have been to offer a selective vaccination only to adolescents with a negative history of chickenpox; or at least to delay the beginning of the universal campaign in the Italian regions that had not started the mass vaccination yet, evaluating the results over time. Lastly, this paper lists a number of preventive interventions of proven effectiveness and cost-effectiveness, with extraordinary margins of improvement, whose mandatory introduction in the population have never been considered, even as a matter of debate.

Seroprevalence of varicella zoster virus in Colombo district, Sri Lanka

Objective: To determine the seroprevalence of varicella zoster virus (VZV) antibodies among the population residing in the Colombo district of Sri Lanka. Methods: A cross-sectional population-based study was conducted which included 1 258 participants. Blood samples were collected and questionnaires administered to obtain sociodemographic information and history of varicella and/or herpes zoster. Serum samples were assayed for VZV IgG antibodies using a commercial enzyme-linked immunosorbent assay kit. Results: Overall, the seroprevalence was 54.2% (95% CI = 51.5% 57.0%). Children below 1 year of age were seronegative, and only about 20.0% of children between 1 and 10 years of age were seropositive. Seropositivitiy increased with age and by the age of 40 years 74.3% were seropositive. Among women of childbearing age, the overall seroprevalence was about 62.0% (95% CI = 57.7%-66.1%) but was low 37.0% in the 15-19 age group. Conclusion In this population, 45.8% lacked natural immunity against varicella. Of women of childbearing age, 39.9% lacked immunity and in the subgroup of women 15-19 years of age, 63.0% women lacked immunity. In light of the country's success with the control and high coverage of other vaccine preventable diseases and that the vaccine is available in the private sector, the inclusion of varicella vaccine in the national immunization program may be considered.

Varicella infection in the Middle East: Prevalence, complications, and vaccination.

Varicella (chickenpox) is the primary infection of varicella-zoster virus (VZV), it is a mild self-limiting infection, but it is also highly contagious and can cause severe complications among high-risk group of individuals. It is usually a childhood infection providing lifelong immunity, but adults without varicella history are also susceptible to infection. High-risk group of individuals is more likely to develop serious complications. Varicella vaccine was introduced to protect this group of individuals and to prevent epidemic spread of VZV infection in a community. Thus, it was added to the recommended vaccination schedules for children in most developed countries. This review aimed to outline varicella status, seroprevalence, complications, and vaccination in the Middle East region. Based on our findings, children were the most affected age group, but there are also adult cases due to high number of expatriates, especially in Gulf Cooperation Council countries. Central nervous system involvements and skin diseases followed by varicella pneumonia were the most varicella-associated complications. Varicella vaccine was introduced in most Middle East countries, either mandatory by the Ministries of Health or optional in the private clinics. Few numbers of studies have reported an obvious reduction in varicella prevalence, hospitalizations, and deaths in the Middle East following varicella vaccination. A basic database about varicella infection before the initiation and implementation of a vaccination policy is essential to determine the target group of individuals. As far as our knowledge, this is the first review about varicella infection in the Middle East.

An outbreak of chickenpox in an asylum seeker centre in Italy: outbreak investigation and validity of reported chickenpox history, December 2015-May 2016.

An outbreak of chickenpox occurred between December 2015 and May 2016 among asylum seekers in a reception centre in Latium, Italy. We describe the epidemiological and laboratory investigations, control measures and validity of reported history of chickenpox infection. Serological screening of all residents and incoming asylum seekers was performed, followed by vaccine offer to all susceptible individuals without contraindication. Forty-six cases were found and 41 were associated with the outbreak. No complications, hospitalisations or deaths occurred. Serological testing was performed in 1,278 individuals and 169 were found to be susceptible, with a seroprevalence of 86.8%. A questionnaire was administered to 336 individuals consecutively attending the CARA health post to collect their serological result. The sensitivity, specificity and the positive and negative predictive value (PPV and NPV) of the reported history of chickenpox were 45.0%, 76.1%, 88.3% and 25.6%, respectively. We observed an increasing trend for the PPV and decreasing trend for the NPV with increasing age. Our report confirms that, in the asylum seeker population, chickenpox history is not the optimal method to identify susceptible individuals. Our experience supports the need for additional prevention and control measures and highlights the importance of national and local surveillance systems for reception centres.

Multidermatomal Herpes Zoster in an Immunocompromised Patient-A Case Report

Multi-dermatomal involvement is uncommon in varicella zoster infection and indicates underlying immunosuppression. A 43 years old male, a known diabetic presented with painful papulovesicular lesions over the left side of the chest, back, arms and forearm with the history of chickenpox one month back. On evaluation for an unusual presentation, he was found to be reactive to HIV. Diagnosis of HZ was confirmed by HZV PCR. He was treated with antivirals, insulins, pain management and care of the lesions. The occurrence of the multi dermatomal herpes zoster with bilaterally symmetrical involvement immediately the following chickenpox is a rare observation and needs to be reported.

Effectiveness of varicella vaccine as post-exposure prophylaxis during a varicella outbreak in Shanghai, China

ObjectivesVaricella vaccine (VarV) is recommended as effective post-exposure prophylaxis (PEP) within 3–5days to control outbreaks. However, the effectiveness of PEP at >5days after exposure and the administration of a second dose to those with a history of one dose prior to exposure have not been fully examined. This study evaluated the vaccine effectiveness (VE) of PEP in preventing disease during a varicella outbreak in Shanghai, China in 2013. MethodsSelf-administered questionnaires were used to obtain the students’ varicella history, vaccination status, and willingness to receive PEP. One dose of VarV was provided free of charge to eligible students. The VE of PEP was calculated as [1−relative risk (RR)]×100%. Analyses were restricted to grade 8 students, as no students from the other grades or teachers developed varicella during the outbreak. ResultsTwenty-seven varicella cases were identified, 16 (59%) of which were infected after the PEP campaign. Sixty-five students received one dose of VarV on day 13 or 19 after the index case. Attack rates were 28% (9/32), 16% (15/94), 0% (0/10), and 6% (3/55) among unvaccinated, one-dose Pre-PEP, first dose as PEP, and second dose as PEP recipients, respectively. Cases among second dose as PEP recipients tended to have less fever compared with unvaccinated or one-dose Pre-PEP recipients. Compared with unvaccinated students, the VE of first dose as PEP recipients was 100% and of the second dose as PEP recipients was 60% (95% confidence interval −72% to 91%). ConclusionsPost-exposure vaccination should be given as soon as possible after exposure. Nevertheless, vaccination is still recommended even at more than 5days post-exposure to control varicella outbreaks.

Serological Susceptibility to Varicella Among U.S. Immigration and Customs Enforcement Detainees.

U.S. Immigration and Customs Enforcement (ICE) is responsible for detaining unauthorized aliens during immigration proceedings. During 2014 to 2015, adult ICE detainees at a California facility were invited to complete a survey concerning self-reported varicella history and risk factors. Participants underwent serological testing for varicella-zoster virus (VZV) IgG; susceptible individuals were offered varicella vaccination. Among 400 detainees with available serology results, 48 (12%) were susceptible to varicella. Self-reported varicella history was negatively associated with susceptibility (adjusted odds ratio = 0.16; 95% confidence interval [0.07, 0.35]). Among 196 detainees reporting a positive history, 95% had VZV IgG levels suggestive of varicella immunity. Among 44 susceptible detainees offered vaccination, 86% accepted. Given relatively high varicella susceptibility, targeted screening and vaccination among ICE detainees lacking a positive history might reduce varicella transmission risks.

Prevalence of a history of prior varicella/herpes zoster infection in multiple sclerosis

Varicella zoster virus (VZV) infection has been implicated in multiple sclerosis (MS), but direct causal involvement has been disputed. Nevertheless, knowledge of VZV exposure is important, given the risk of serious complications of first exposure while undergoing immunosuppressive treatment, in particular with fingolimod. We distributed questionnaires to MS clinic patients, requesting information about history of chickenpox, sibling/household/occupational exposure, history of zoster (shingles), and disease-modifying treatment. A random, proportionally representative sample of 51 patients that included patients with positive, negative, and unknown chickenpox history were selected for determination of VZV IgG by ELISA. Of 1206 distributed questionnaires, 605 were returned (50% response rate). Of these, 86% reported history of chickenpox, 5.6% gave negative history, and 8.5% did not know. Of 594 who answered the zoster question, 78% gave a negative response, 4% did not know, and 104 (17%) answered yes. Of these, 83 reported 1 episode; 12 had 2; 5 had 3; and 1 each reported 5, 6, and 15 episodes. Of 51 patients tested for VZV IgG (44 “yes,” 4 “no,” and 3 “I don’t know” answers to the question of whether they had chickenpox), 48 were seropositive; the 3 seronegative all had reported having had chickenpox. The high rate of MS patients reporting prior chickenpox infection is comparable with previous reports. A substantial proportion of MS patients, estimated to be higher than an age-matched general population, report single or multiple episodes of zoster. These data are useful for consideration of immunosuppressive treatments and/or VZV and zoster vaccination.

Varicella outbreak in a highly-vaccinated school population in Beijing, China during the voluntary two-dose era.

Two-dose varicella vaccination has been available in Beijing since 2012 in the private sector. We investigated a varicella outbreak in a highly vaccinated elementary school population. A cohort study was carried out and a varicella case was defined as an acute onset of generalized maculopapulovesicular rash without other apparent cause in a student attending the school from March 29 through May 17, 2015. Breakthrough varicella was defined as varicella >42days after the last vaccine dose among both 1- or 2-dose varicella vaccine recipients. Vaccination information was collected from immunization records; information on prior varicella and clinical presentations was collected by surveying students' parents. Of the 1056 students in the school, 1027 (97.3%) reported no history of varicella. Prior to the outbreak, 98.6% of students had received ≥1 dose of varicella vaccine, and most (63.2%) students received two doses. Twenty varicella cases were identified for an overall attack rate of 2.0%. Half of the cases occurred in the classroom of the index case-patient, a two-dose recipient who was not isolated after symptom onset. Breakthrough varicella accounted for 95% of cases (19/20) with attack rates of 14.3% (1/7), 1.6% (6/362) and 2.0% (13/649) among unvaccinated, one-dose, and two-dose students, respectively. Most case-patients (18/20, 90%) had <50 lesions. No difference in clinical presentations was found between one-dose and two-dose recipients with breakthrough varicella. Moderate two-dose varicella vaccine coverage was insufficient to prevent a varicella outbreak. Two-dose recipients with breakthrough varicella are contagious. High two-dose varicella vaccine coverage and timely isolation of cases may be needed for varicella outbreak prevention in the two-dose era.

Seroepidemiology of varicella among elementary school children in northern Taiwan.

In Taiwan, varicella vaccine was included in the expanded program of immunization since 2004. A seroepidemiologic study in the postvaccine era is helpful to evaluate the efficiency of current varicella vaccination strategies. We used a multistage stratified systematic sampling design to classify 29 administrative districts of New Taipei City into five strata. In 2013, a total of 936 students from 14 primary schools were recruited and had blood drawn for serology tests for varicella-zoster virus-immunoglobulin-G via indirect chemiluminescence immunoassays. A history of clinical varicella and information on varicella vaccination status were obtained. Overall, the seroprevalence was 64.1%. For the five strata, the seropositive rate ranged from 54.2% (Stratum 5) to 71.7% (Stratum 2) with no significant difference. For each participating school, the seropositive rate ranged from 44.4% to 72.9% with a statistically significant difference (p<0.005). For school children in each grade, seropositive rate increased significantly from 53.2% for Grade 1 to 71.8% for Grade 3 (p=0.005) and increased steadily from 61.2% for Grade 4 to 71.2% for Grade 6 (p=0.17). A positive correlation was observed between the seropositive rate and geometric mean titers (p=0.035). Geometric mean titers and the rate of a history of clinical varicella were positively correlated with increasing class grades. Nine years after the introduction of the varicella vaccine into the expanded program of immunization in Taiwan, around two-thirds of elementary schoolchildren were seropositive for varicella-zoster virus. Further surveillance studies on clinical varicella cases are worthwhile to determine whether a second dose of varicella vaccine is needed in Taiwan.

Varicella-zoster virus seroprevalence in children and adolescents in the pre-varicella vaccine era, Germany

BackgroundIn 2004, universal childhood varicella vaccination was introduced in Germany. We aimed to determine the age-specific prevalence of anti-varicella zoster virus (VZV) IgG-antibodies among children in the pre-varicella vaccine era in Germany, to identify factors associated with VZV seropositivity, and to assess the suitability of a commercially available ELISA for VZV seroepidemiological studies by comparing it with an in-house fluorescent antibody to membrane antigen test (FAMA) as the gold standard.MethodsSerum samples of 13,433 children and adolescents aged 1–17 years included in the population-based German Health Interview and Examination Survey for Children and Adolescents (KiGGS; conducted 2003–2006) were tested for anti-VZV IgG by ELISA. All samples with equivocal ELISA results and a random selection of ELISA-negative and -positive samples were tested by FAMA. Statistical analyses were conducted using a weighting factor adjusting the study population to the total population in Germany. Seroprevalences were calculated as percentages (%) with a 95% confidence interval (CI). Odds ratios (OR) were computed by multivariate logistic regression to determine the association between socio-demographic factors and VZV seropositivity.ResultsThe VZV seropositivity rate was 80.3% (95% CI: 79.3–81.3) in varicella-unvaccinated children and adolescents. VZV seropositivity rates differed significantly between age groups up to age 6 years, but not by gender. Of 118 retested serum samples with an equivocal ELISA result, 45.8% were FAMA-positive. The proportion of samples tested as false-negative in by ELISA varied by age group: 2.6% in children aged 1–6 and 9% in children aged 7–17 years. Multivariate analyses showed that age, having older siblings, and early daycare start were associated with seropositivity in preschoolers; migration background reduced the chance of VZV seropositivity in schoolchildren (OR: 0.65; 0.43–0.99) and adolescents (OR: 0.62; 0.4–0.97).ConclusionIn the pre-varicella vaccine era, most children in Germany contracted varicella by age six. Schoolchildren with a migration background and children without siblings have an increased risk of being VZV seronegative and should be targeted for catch-up vaccination, if they have no history of chickenpox. ELISAs are suitable for use in population-level serosurveys on VZV, but samples with equivocal ELISA results should be retested by FAMA.

Can a healthcare worker be a source of an infection of a patient – a risk of transmitting the chickenpox and shingles virus VZV by the staff of hospital wards – preliminary research findings.

Introduction. Chickenpox is a highly infectious disease, caused by the Varicella-zoster virus. An infection during pregnancy poses particular risk, as it may have serious consequences for both the pregnant woman and the fetus. The only effective and safe method of preventing chickenpox is protective vaccination.Aim. This study aims to assess the risk of contracting the Varicella-zoster infection in a selected population of hospital workers, as well as the further transmission of the virus to newborns, mothers and older children.Materials and Methods. A survey was conducted in September 2014 in three public hospitals in Poznań, among nurses and midwives working in paediatric, neonatal and maternity wards. 136 nurses and midwives participated in the survey.Results. The analysis of the findings reveals that 114 staff members of the hospital wards, i.e. 83.82%, have had chickenpox in the past, 14 respondents (10.29%) have never had this illness, and 8 (5.88%) do not know if they have been ill, which means that 16% of the respondents could potentially contract chickenpox. For the majority of nurses and midwives (103) the infection had taken place before they started work. However, 11 respondents (8,08) were infected during employment.Conclusions. 1) Nearly one out of 4 hospital staff members had no history of chickenpox contraction at the beginning of their employment. 2) Nearly 15% of the workers confirm that at the beginning of employment their immunity status was established on the basis of an interview. 3) The majority of employees negatively interviewed for chickenpox history have not been recommended to be vaccinated against this disease.

Knowledge, attitudes, and behaviors of parents towards varicella and its vaccination

BackgroundThe aims of this cross-sectional survey were to examine the knowledge, the attitudes, and the behavior regarding the varicella infection and its vaccination and to get insight into their determinants among parents of children in Italy.MethodsFrom May to June 2015 in the geographic area of Naples (Italy) a random sample of 675 parents of children aged 4-7 years received a self-administered anonymous questionnaire about socio-demographic characteristics, knowledge, attitudes, and behaviors towards varicella and its vaccination.ResultsA total of 414 parents responded to the questionnaire, for a response rate of 61.3%. A history of varicella was reported in 163 children (39.6%). Only 26.6% parents knew that the vaccine was available and the number of doses and this knowledge was significantly higher in those who had a university degree, in those who had received information on the vaccination from a health care provider, and in those who had vaccinated their child. The perceived utility towards vaccination had a mean value of 5.7. The positive attitude towards the utility of the vaccination was higher in parents with a level of education not higher than middle school, in those who had vaccinated their child, in those who considered the varicella a dangerous disease, and in those who had received information from a health care provider. More than one-third had vaccinated their child. Immunization was more frequent in parents who had knowledge about the vaccination, who beliefs that the immunization was useful, who believed that the disease was not dangerous, and who had not a history of varicella among their children.ConclusionsEducational programs are needed among parents as support to improve knowledge about vaccination and immunization coverage.

Genotype analysis of ORF 62 identifies varicella-zoster virus infections caused by a vaccine strain in children.

This study was performed to differentiate vaccine-type strains from wild-type strains and determine the genotype of varicella-zoster virus (VZV) in 51 Korean children. A sequencing analysis of ORF 62 identified two cases of herpes zoster caused by the vaccine-type virus, without a previous history of varicella, 22months and 5months after VZV vaccination. The wild-type strain was identified in the remaining children. A genotype analysis of ORF 22 amino acids revealed genotype J in all children except one. Genotype E was identified in an infant with varicella imported from Egypt.

Varicella - a potential threat to maternal and fetal health.

The aim of the study was to evaluate the following: i) number of midwives and nurses at risk for contracting varicella; ii) effectiveness of infectious disease prevention among healthcare personnel; iii) attitude of healthcare person-nel towards immunization. A total of 524 midwives and nurses from obstetric, neonatal, and pediatric wards were investigated. Quantitative data analysis was performed. Overall, 14.7% potentially seronegative respondents were identified. Out of those with a positive history of varicella, 6.56% contracted the disease after starting work, and > 70% had contact with the varicella-zoster virus. Overall, 9.54% of the respondents had a history of varicella, 3.12% were informed about the possibility of immunization, and 1.56% of those with a negative history of the disease were offered a state-funded vaccine. In the same group, the number of vaccinated people amounted to 13.28%, and 26.13% would accept a state-funded vaccine. Varicella may constitute a significant threat to maternal and fetal health at obstetric, neonatal, and pediatric wards, which must be considered when providing care to women in the reproductive age. Occupational health physicians should confirm the immunity status of the patients and suggest immunization to seronegative subjects. Regular workshops are necessary to update the knowledge of medical professionals and patients in order to shape their attitudes and beliefs about immunization.

P486 Immunization status of children and adolescents with inflammatory bowel disease or autoimmune hepatitis in Germany

Background: Long-term immunosuppressed patients with inflammatory bowel disease (IBD) and autoimmune hepatitis (AIH) are at risk of severe infections with vaccination preventable diseases. Several recent studies demonstrated insufficient immunization coverage in children and adolescents with IBD. Therefore, we evaluated the vaccination rate of children and adolescents with IBD and AIH in Germany. Methods: As part of the German multicentre clinical trial called “VARICED”, the immunization rate of patients with IBD and AIH below 18 years of age was assessed from the certificate of vaccination, medical history of chicken pox and by analysing varicella zoster virus (VZV) IgG and measles virus IgG antibody titres by ELISA. Results: To date 229 patients (51% female, mean age at diagnosis 9.9 years) are registered: 137 have Crohn's disease (CD), 53 ulcerative colitis (UC), 19 IBD-unclassified (IBD-U) and 20 AIH. The majority of the patients (n=190, 83%) are on immunosuppressive therapy (AIH 100%, CD 89%, UC 68%). A complete basic immunisation consisting of 4 doses of a hexavalent vaccine were given to 89% of the total cohort. A combined inoculation for measles, mumps, and rubella (MMR) was documented in 225 (98%) patients, 208 (92%) received two doses. VZV vaccination was introduced in 2004 to the vaccination schedule from the German Standing Committee on Vaccination (STIKO). A good implementation with 90% was found in the birth cohorts from 2005 onwards. In children born before 2005 (n=190) only 22% received VZV vaccination catch up. VZV vaccination was documented in only 77 (34%) patients, but 17 patients (22%) did not display sufficient VZV IgG titres. Already 144 (63%) patients had a medical history of chicken pox. However, three of them did not have verifiable VZV IgG antibodies. In addition, 37 patients had neither a history of a chicken pox infection nor VZV inoculation, but 11 out of them were found to have sufficient VZV IgG titres. Conclusions: There is a good implementation of the vaccination schedule from the German Standing Committee on Vaccination (STIKO) in the group of children and adolescents with IBD and AIH. Our data suggests a gap in VZV immunity in birth cohorts before 2005 in Germany. Moreover, neither the certificate of vaccination nor the medical history of chicken pox infection is reliable for assessing VZV immunity. Serologic investigations demonstrated that some non-immunized patients may undergo occult immunization, and immunized patients did not present sufficient VZV-IgG titres. Thus, we recommend VZV IgG serology within the check-up in newly diagnosed IBD or AIH and VZV vaccination before initiating immunosuppressive therapy, if applicable.

RISK FACTORS FOR MULTIPLE SCLEROSIS IN VOLYN REGION (UKRAINE)

The prevalence rate of multiple sclerosis (MS) in Volyn Region (101.0 per 100000) is the highest in Ukraine. To study MS risk factors in Volyn Region, special questionnaires were distributed among all MS patients residing in Volyn region. Results were obtained from 227 respondents including 154 women and 73 men of mean age 43±10.6 years. The control group included 105 healthy respondents inhabiting Volyn region. We found associated risk factors for MS to be: mother of Volyn origin, maternal age after 27 years old and paternal age after 29 years old at birth of respondent, subject's born as a third child, brestfeeding for less than one year, living in the zone of industrial pollution, near mobile, TV- and radio re-translators, full traffic automobile roads, time spending outdoors less than one hour in winter and less than eight hours in summer, consumption of fruit and vegetables less than 5 times a week, of beef less than 3 times a week, poultry meet less than 3, berries less than 3, cereals less than 4 times a week, chronic stressful situations in life. Patients with MS more frequently reported AVRI, hepatitis and herpes simplex virus. Among patients with MS there were fewer respondents with history of chickenpox, rubella and DPT (diphtheria, pertussis, tetanus), BCG immunizations. Here, we introduced a novel study of MS risk factors within Volyn Region. The Registry established in 2012 is being constantly updated and can be a database for a long-term retrospective study involving a large number of patients.

Varicella seroprevalence in individuals with a negative or unknown varicella history - results from a large travel clinic in Switzerland between 2008 and 2015.

In Switzerland, vaccination against varicella is not recommended in the basic immunisation schedule. However, for individuals aged 11-40 years who do not have a reliable varicella history the Swiss Federal Office of Public Health recommends either (i) a vaccination or (ii) a serology test and vaccination of those with a negative result. In the Travel Clinic of the University of Zurich, the second strategy is followed. In this study we retrospectively assessed the overall percentage of individuals with varicella-specific antibodies despite a negative history and we examined the influence of age, number of siblings, order of siblings, age difference to siblings and nationality on varicella seropositivity. Between December 2008 and August 2015, the sera of 1757 individuals with a negative varicella history were tested for varicella antibodies. A total of 1593 individuals (91%) had a positive result. We found an increasing trend for varicella seropositivity with increasing age. Those aged less than 40 years were significantly more often seronegative (9.5%) than those aged 40 years and above (6.0%, p = 0.049). Seropositivity was associated with nationality. The percentage of seropositives increased with the number of siblings. Our results indicate that, despite the significant varicella seropositivity differences between those aged below and above, the age of 40 may not be an ideal threshold for performing a varicella serology in individuals with a negative or unknown varicella history. In the age groups above 40, testing for varicella antibodies may be especially reasonable in individuals with no or a small number of siblings and in those of specific nationalities.

Prevalence and Characteristics of Pediatric Healthcare Workers without Immunity to Varicella zoster Virus.

This study aimed to determine the proportion of varicella non-immune pediatric healthcare workers (HCWs) of the Pediatrics Department of King Chulalongkorn Memorial Hospital and to determine cost-effective strategies for identifying non-immune personnel. A cross-sectional study using a self-administered questionnaire to determine HCWs' histories of chickenpox or 2-dose varicella vaccination was conducted. From a total of 699 HCWs, 653 HCWs (93%), including 145 physicians (22%), 297 nurses (46%), and 211 administrative staff (32%), responded to questionnaires. There were 475 HCWs (73%) who had a history of chickenpox, 58 (9%) who had completed the 2-dose varicella vaccine schedule, and 120 (18%) whose varicella-zoster virus (VZV) immunity status was uncertain. In total, 107 HCWs (89%) were tested for VZV IgG, 90 of whom had immunity, and 17 were determined to be non-immune. After combining history and VZV IgG test results, the prevalence of non-immune HCWs was 2.6% (95%CI 1.4-3.8), with those ≤40 years of age at higher risk of non-immunity. Implementing a strategy that involves testing of only those with an unknown VZV status and vaccination for only those determined to be non-immune costs 1,801 United States dollar (USD), less than the total cost (4,601 USD) for vaccinating all HCWs with uncertain status.