Seroepidemiology of varicella-zoster virus infection in Catalonia (Spain). Rationale for universal vaccination programmes

Epidemiological and clinical characteristics and the approach to infant chickenpox in primary care

Chickenpox is not common in the first year of life (infant varicella) and there is a lack of data on its presentation, especially in primary care. A year-long observational study (July 2015-2016) carried out by a research network of primary care pediatricians throughout Spain.Two hundred and sixty-four pediatricians gathered data from 358 cases of clinically diagnosed chickenpox in infants. The illness was considered mild in 78% of infants < 7 months compared to 65% in those aged 7 to 12 months (p = 0.0144). Fever (46%) was present in 35% of children ≤ 6 months compared to 55% in older children (p = 0.0005). The number of skin lesions was > 50 in 35% of children ≤ 6 months old compared to 47% in > 7 months (p = 0.0273). From the 2% of hospitalized children 86% were younger than 7 months. Oral antiviral treatment was given in 33% of cases ≤ 6 months compared to 18% in older patients (p = 0.0023). Doubts about administering the chickenpox vaccine at a later date were expressed by 18% of pediatricians.Conclusion: Chickenpox is considered benign, having a mild effect on most infants. There is less clinical effect in infants ≤ 6 months although this age group is hospitalized more and is prescribed more antiviral treatment. There are doubts among pediatricians about the subsequent need for vaccination. What is Known: • Chickenpox is uncommon and of uncertain evolution in the first year of life • Hospital admissions for chickenpox are more frequent in the first year of life What is New: • The course of chickenpox in the first year of life is mild, especially in infants younger than 7 months despite the fact they are hospitalized more and are treated more frequently with antivirals. Antivirals are prescribed to 1 in 4 children with chickenpox under 12 months of age. • Almost 50% of pediatricians recommend a subsequent vaccination against chickenpox especially if it occurs in the first 6 months of life.

Epidemiology, treatment and prevention of herpes zoster: A comprehensive review

Herpes zoster is a major health burden that can affect individuals of any age. It is seen more commonly among individuals aged ≥50 years, those with immunocompromised status, and those on immunosuppressant drugs. It is caused by a reactivation of varicella zoster virus infection. Cell-mediated immunity plays a role in this reactivation. Fever, pain, and itch are common symptoms before the onset of rash. Post-herpetic neuralgia is the most common complication associated with herpes zoster. Risk factors and complications associated with herpes zoster depend on the age, immune status, and the time of initializing treatment. Routine vaccination for individuals over 60 years has shown considerable effect in terms of reducing the incidence of herpes zoster and post-herpetic neuralgia. Treatment with antiviral drugs and analgesics within 72 hours of rash onset has been shown to reduce severity and complications associated with herpes zoster and post-herpetic neuralgia. This study mainly focuses on herpes zoster using articles and reviews from PubMed, Embase, Cochrane library, and a manual search from Google Scholar. We cover the incidence of herpes zoster, gender distribution, seasonal and regional distribution of herpes zoster, incidence of herpes zoster among immunocompromised individuals, incidence of post-herpetic neuralgia following a zoster infection, complications, management, and prevention of herpes zoster and post-herpetic neuralgia.

Estimation of the burden of varicella in Europe before the introduction of universal childhood immunization

BACKGROUND

Varicella is generally considered a mild disease. Disease burden is not well known and country-level estimation is challenging. As varicella disease is not notifiable, notification criteria and rates vary between countries. In general, existing surveillance systems do not capture cases that do not seek medical care, and most are affected by underreporting and underascertainment. We aimed to estimate the overall varicella disease burden in Europe to provide critical information to support decision-making regarding varicella vaccination.

METHODS

We conducted a systematic literature review to identify all available epidemiological data on varicella IgG antibody seroprevalence, primary care and hospitalisation incidence, and mortality. We then developed methods to estimate age-specific varicella incidence and annual number of cases by different levels of severity (cases in the community, health care seekers in primary care and hospitals, and deaths) for all countries belonging to the European Medicines Agency (EMA) region and Switzerland.

RESULTS

In the absence of universal varicella immunization, the burden of varicella would be substantial with a total of 5.5 million (95% CI: 4.7-6.4) varicella cases occurring annually across Europe. Variation exists between countries but overall the majority of cases (3 million; 95% CI: 2.7-3.3) would occur in children <5 years. Annually, 3-3.9 million patients would consult a primary care physician, 18,200-23,500 patients would be hospitalised, and 80 varicella-related deaths would occur (95% CI: 19-822).

CONCLUSIONS

Varicella disease burden is substantial. Most cases occur in children <5 years old but adults require hospitalisation more often and are at higher risk of death. This information should be considered when planning and evaluating varicella control strategies. A better understanding of the driving factors of country-specific differences in varicella transmission and health care utilization is needed. Improving and standardizing varicella surveillance in Europe, as initiated by the European Centre for Disease Prevention and Control (ECDC), is important to improve data quality to facilitate inter-country comparison.

Herpes zoster and postherpetic neuralgia in Catalonia (Spain)

The objective of the study was to analyze the descriptive epidemiology and costs of herpes zoster (HZ) and postherpetic neuralgia (PHN) in people aged ≥50 years in Catalonia (Spain). The incidence of HZ in Catalonia was estimated by extrapolating the incidence data from Navarre (Spain) to the population of Catalonia. The incidence of PHN was estimated according to the proportion of cases of HZ in the case series of the Hospital del Sagrado Corazón de Barcelona that evolved to PHN. Drug costs were obtained directly from the prescriptions included in the medical record (according to official prices published by the General Council of the College of Pharmacists). The cost of care was obtained by applying the tariffs of the Catalan Health Institute to the number of outpatient visits and the number and duration of hospital admissions. The estimated annual incidence of HZ was 31 763, of which 21 532 (67.79%) were in patients aged ≥50 years. The respective figures for PHN were 3194 and 3085 (96.59) per annum, respectively. The mean cost per patient was markedly higher in cases of PHN (916.66 euros per patient) than in cases of HZ alone (301.52 euros per patient). The cost increased with age in both groups of patients. The estimated total annual cost of HZ and its complications in Catalonia was € 9.31 million, of which 6.54 corresponded to HZ and 2.77 to PHN. This is the first Spanish study of the disease burden of HZ in which epidemiological data and costs were collected directly from medical records. The estimated incidence of HZ is probably similar to the real incidence. In contrast, the incidence of PHN may be an underestimate, as around 25% of patients in Catalonia attend private clinics financed by insurance companies. It is also probable that the costs may be an underestimate as the costs derived from the prodromal phase were not included. In Catalonia, HZ and PHN cause an important disease burden (21 532 cases of HZ and 3085 de PHN with an annual cost of € 9.31 million) in people aged ≥50 years, in whom vaccination is indicated.

Seroprevalence of varicella-zoster virus infection in children from Cochabamba: tropical or temperate pattern?

OBJECTIVES

To determine the seroprevalence of varicella-zoster viral (VZV) infections in schoolchildren from the Cochabamba region (Bolivia), and its association with socio-demographic variables, socio-economic status and geographical location.

METHODS

Seroepidemiological survey (n = 436) on VZV of schoolchildren living in the Cochabamba region of Bolivia in 2010. An ELISA test was used to measure varicella antibodies. Parents or guardians completed a questionnaire regarding socio-demographic information (age, gender, living area, parental educational level, presence of siblings and number of family members in the household), and a blood sample was collected from each child to check for VZV antibodies. A descriptive and bivariate analysis was performed.

RESULTS

The global prevalence of VZV was 78.2% (95% CI 74.3-82.1). It was higher in females (82.1%), pre-adolescents (aged 10.1-13 years: 81.4%) and adolescents (aged >13 years: 80.2%), in children with less well-educated parents (81.3% to 81.6%), in warmer municipalities (81.4% to 82.2%), in rural areas (80.0%), in children with siblings (80.1%), those who although the latter association was not statistically significant.

CONCLUSIONS

The prevalence of VZV infection in childhood was relatively high for a tropical country, and much closer to that of temperate countries prior to the introduction of varicella vaccine into vaccination programmes.

Seroprevalence of varicella-zoster virus and predictors for seronegativity in the Amsterdam adult population

BACKGROUND

In the Netherlands, infection with varicella-zoster virus (VZV) is considered a benign common childhood illness and routine vaccination against VZV is not done. In 1995 it was estimated that 98-100% of the adult Dutch general population is immune, yet the estimate is based on a database in which a relative small number of people of non-Dutch ethnic origin were represented. As the city of Amsterdam has large immigrant communities originating from various subtropical and tropical countries, such as Morocco, Surinam, and Turkey with probably lower VZV transmission, this study aimed to estimate the seroprevalence of VZV IgG antibodies (anti-VZV) among various ethnic groups in Amsterdam, and identify factors associated with seronegative VZV status.

METHODS

The study was a cross-sectional survey of the Amsterdam population (2004), and the study sample was stratified by age and ethnicity, with deliberate oversampling of minority ethnic groups. Serum samples obtained from 1,341 residents in 2004 were tested for antibodies to VZV. Basic demographic data (gender, age, country of birth, age at immigration and number of children) were also available.

RESULTS

The anti-VZV seroprevalence in the overall Amsterdam population was estimated to be 94% (95% confidence intervals; 92-96%). Regarding ethnic origin, first generation immigrants (Moroccan immigrants 90%, Surinamese or Antillean immigrants 91%, and Turkish 92%), especially those that migrated after the age of 11 years, were more likely to be anti-VZV seronegative compared to those arriving at an earlier age or those born in the Netherlands (97-98%). Both ethnic origin and generation of immigration were positive predictors for IgG seronegativity to VZV (p<0.015). No other predictors for seronegativity were found.

CONCLUSION

The results of this study imply that about 4-8% of the general adult Amsterdam population is still susceptible to infection with VZV, and that susceptibility is even higher in some immigrant groups. When assessing the risk of infection after VZV exposure alertness is needed for vulnerable persons like pregnant women, patients with hematological malignancies or organ transplants in particular among first-generation immigrants.

Contacts with children and young people and adult risk of suffering herpes zoster

We carried out a matched case-control study to analyze the possible association between exposure to the children and the risk of suffering herpes-zoster in adulthood. Cases of herpes zoster in immunocompetent healthy patients aged ≥ 25 years seen in the dermatology department of the Sagrado Corazón Hospital in 2007-2008 were matched with four controls. Data were analyzed using conditional logistic regression. 153 cases and 604 matched controls were included. Contacts with children were significantly associated with a reduction in the risk of suffering herpes zoster in adulthood (adjusted OR 0.56 [0.37-0.85]). Herpes-zoster vaccination in immunocompetent people aged ≥ 50 years could counteract the possible negative effects of mass varicella vaccination in childhood on the epidemiology of herpes zoster in adults.

Seroepidemiology of varicella-zoster virus and reliability of varicella history in Turkish children, adolescents and adults

This study aimed to assess the age specific varicella-zoster virus (VZV) seroprevalence in Izmir, Turkey and to determine the reliability of a history of varicella to detect susceptible children, adolescents and adults. A questionnaire, including previous history of varicella, was completed for each participant and, in 590 of them, VZV-specific IgG was measured using an ELISA test. Overall, 28.5% of individuals were seronegative for VZV. By 5 years of age, only 25.5% of children were seropositive for VZV. Among adolescents and young adults, 18.8% and 11.7% were seronegative, respectively. The negative predictive value was 57.8%, decreasing with age (81.9% in children, 34.5% in adolescents and 8.3% in adults). In conclusion, a negative history of varicella is not a reliable predictor of varicella antibody status in adolescents and young adults. Serological testing before immunisation will be logical, rather than presumptive vaccination, for adolescents and adults with negative history of varicella.

Varicella susceptibility and transmission dynamics in Slovenia

BACKGROUND

A cross-sectional, age-stratified study was conducted to determine varicella-zoster seroprevalence and force of infection in Slovenia.

METHODS

3689 serum samples were tested for VZV IgG antibodies with an enzyme immunoassay. Semiparametric and parametric modelling were used to estimate the force of infection.

RESULTS

Overall, 85.6% of serum samples were seropositive. Age-specific prevalence rose rapidly in preschool children and over 90% of 8 years old tested positive for VZV. However, 2.8% of serum samples among women of childbearing age were seronegative. Semiparametric modelling yielded force of infection estimates of 0.182 (95% CI 0.158-0.206), 0.367 (95% CI 0.285-0.448) and 0.008 (95% CI 0.0-0.032) for age groups 0.5- < 6, 6-11 and >or=12 years, respectively, and 0.175 (95% CI 0.147-0.202), 0.391 (95% CI 0.303-0.480) and 0.025 (95% CI 0.003-0.046) for age groups 0.5- < 5, 5-9 and >or=10 years, respectively.

CONCLUSIONS

Regardless of the age grouping used, the highest transmission occurred in children in their first years of school.

Effectiveness of varicella vaccines as postexposure prophylaxis

BACKGROUND

Although chickenpox is usually a mild disease, it is not always free of complications, especially in adolescents and adults. Previous studies of postexposure prophylaxis conducted with experimental vaccines showed the vaccine to be highly effective if administered in the first 3 to 5 days after exposure. However, studies carried out with commercialized vaccines yielded discordant results. The aim of the present study was to assess the effectiveness of currently available varicella vaccines as postexposure prophylaxis.

METHODS

We conducted a prospective cohort study. Patients susceptible to chickenpox consulting at the Preventive Medicine Department of the Vall d'Hebron Hospital after household exposure to a case of chickenpox were included. Postexposure prophylaxis with varicella vaccine was administered within the first 5 days after contact. Subjects were interviewed by telephone between 4 and 8 weeks after vaccination to ascertain whether chickenpox had appeared and, if so, its severity. The effectiveness of the vaccine in preventing and attenuating the disease was calculated with a confidence interval of 95%.

RESULTS

Sixty-seven subjects were included in the study. Effectiveness of the varicella vaccine in preventing any type of disease was 62.3% (CI 95%: 47.8-74.9) and 79.4% (CI 95%: 66.4-88.9) in preventing moderate and severe disease. No statistically significant differences were found when effectiveness was compared according to sex, age, or days elapsed since exposure.

CONCLUSIONS

Administration of varicella vaccines within the first 5 days postexposure is effective in preventing chickenpox and in attenuating the illness.

Varicella vaccination in Europe - taking the practical approach

Varicella is a common viral disease affecting almost the entire birth cohort. Although usually self-limiting, some cases of varicella can be serious, with 2 to 6% of cases attending a general practice resulting in complications. The hospitalisation rate for varicella in Europe ranges from 1.3 to 4.5 per 100,000 population/year and up to 10.1% of hospitalised patients report permanent or possible permanent sequelae (for example, scarring or ataxia). However, in many countries the epidemiology of varicella remains largely unknown or incomplete. In countries where routine childhood vaccination against varicella has been implemented, it has had a positive effect on disease prevention and control. Furthermore, mathematical models indicate that this intervention strategy may provide economic benefits for the individual and society. Despite this evidence and recommendations for varicella vaccination by official bodies such as the World Health Organization, and scientific experts in the field, the majority of European countries (with the exception of Germany and Greece) have delayed decisions on implementation of routine childhood varicella vaccination, choosing instead to vaccinate high-risk groups or not to vaccinate at all. In this paper, members of the Working Against Varicella in Europe group consider the practicalities of introducing routine childhood varicella vaccination in Europe, discussing the benefits and challenges of different vaccination options (vaccination vs. no vaccination, routine vaccination of infants vs. vaccination of susceptible adolescents or adults, two doses vs. one dose of varicella vaccine, monovalent varicella vaccines vs. tetravalent measles, mumps, rubella and varicella vaccines, as well as the optimal interval between two doses of measles, mumps, rubella and varicella vaccines). Assessment of the epidemiology of varicella in Europe and evidence for the effectiveness of varicella vaccination provides support for routine childhood programmes in Europe. Although European countries are faced with challenges or uncertainties that may have delayed implementation of a childhood vaccination programme, many of these concerns remain hypothetical and with new opportunities offered by combined measles, mumps, rubella and varicella vaccines, reassessment may be timely.

A new challenge for Europe: introducing a pediatric quadrivalent vaccine for measles, mumps, rubella, and varicella

BACKGROUND

Varicella is often considered to be a benign disease of childhood. In fact, varicella is associated with serious complications and mortality even among healthy individuals.

DISCUSSION

Although the course of varicella can be uncomplicated, it can also be associated with serious complications such as pneumonia, fluid and electrolyte disturbances, skin and soft tissue infections and central nervous system disturbances. Worldwide studies have confirmed the high frequency of disease as well as the resultant morbidity, mortality and medical resource use. A quadrivalent vaccine is now available in certain countries to protect against measles, mumps, rubella and varicella (MMRV). Countries that have initiated routine vaccination pro- grams have reported substantial reductions in morbidity and mortality as well as improved health outcomes. The MMRV vaccine facilitates coverage against all four diseases, and would be expected to improve compliance as well as coverage of varicella.

CONCLUSIONS

Universal vaccination programs with MMRV should be considered as a way to reduce the medical and economic impact of varicella. The MMRV vaccine provides a means to achieve universal coverage.

Varicella vaccination in Europe: are we ready for a universal childhood programme?

Safe and effective vaccines against varicella zoster virus (VZV), the aetiological agent of varicella and shingles, have been available in Europe for the last 5-10 years. The USA has had a universal childhood vaccination policy since 1995 and this has resulted in a dramatic decrease in the incidence, morbidity and mortality related to varicella. The economic and medical burden of VZV has led to discussions regarding both the desirability and feasibility of a similar routine immunisation policy for all European children. This article examines the epidemiology of varicella in Europe and how the data emerging from the USA can be used to achieve adequate prevention of the disease. It looks into the current evidence of the health economic evaluation of universal varicella vaccination and explores the concerns surrounding such a policy, including the postulated impact on the incidence of zoster. In conclusion, the Society of Independent European Vaccination Experts (SIEVE) recommends that the immunisation of susceptible adolescents needs to be urgently implemented, in addition to the current recommendations targeting high-risk patients, their close contacts with a negative history of varicella and seronegative health-care workers. A universal policy, optimally incorporating a two-dose schedule, will be needed to finally reduce the burden of disease of varicella from a societal point of view. The SIEVE recommends the implementation of such a policy as soon as financially and practically possible.

Seroprevalence of varicella zoster virus infection in child and adult population of Catalonia (Spain)

The aim of this study was to determine the prevalence of varicella IgG antibodies in the population of Catalonia, and the variables associated. The study was carried out in 2002 in a representative sample of juvenile (5-14 years) and adult population (> or =15 years) of Catalonia (Spain). The global prevalence determined by ELISA test was 95.5% (95% CI 94.7-96.3). The prevalence increased with age, from 82% (95% CI 77.0-87.0) in the 5-9 years age up to 99.4% (95% CI 98.2-100) in >64 years of age. No statistically significant differences in the seroprevalence according to the sociodemographic variables were observed. The current strategy of vaccinating preadolescents at 12 years of age who have not suffered the disease will require more than 30 years to cover the current gap immunity in adolescents and young adults. Vaccination with two doses of vaccine for all adolescents and adults < or = 50 years who report not having suffered the disease during childhood should be considered.

Prevalence of varicella-zoster antibodies in pregnant women in Catalonia (Spain). Rationale for varicella vaccination of women of childbearing age

OBJECTIVE

The objective of this study was to determine the prevalence of antibodies against varicella-zoster virus (VZV) in pregnant women in Catalonia (Spain).

SETTING

The prevalence of antibodies against VZV was assessed in a representative sample (n = 1522) of pregnant women of Catalonia obtained in 2003.

METHOD

The sample was obtained including all women attended for childbirth, during 2 months of 2003, in 27 randomly selected hospitals with maternity clinics.

MAIN OUTCOME MEASURES

Varicella-zoster antibodies were determined using the enzyme-linked immunosorbent assay test.

RESULTS

The total number of women included in the study was 1522, corresponding to a participation rate of 83%. The prevalence of varicella-zoster antibodies in pregnant women was 96.1% (95% CI 95.1-97.1). The prevalence of antibodies was 94% in pregnant women aged 15-24 years, 95% in those aged 25-29 years and >95% in those aged 30-49 years. The prevalence of antibodies was not associated to the place of birth, place of residence (urban or rural), educational level and social class. The study showed that 6% of pregnant women aged 15-24 years and 5% of those aged 25-29 years were susceptible to varicella-zoster infections in Catalonia (Spain).

CONCLUSION

The study showed that a varicella-zoster vaccination programme aimed at women of childbearing age could be necessary in Catalonia to prevent all varicella-zoster infections during pregnancy.

Susceptibility to varicella in childbearing age women, Central Italy: is there a need for vaccinating this population group?

We conducted a cross-sectional seroprevalence study of varicella-zoster virus (VZV) antibodies in childbearing age women aged 17-42 years. Sera were collected in Central Italy in years 2001-2002 and were tested by a commercial VZV IgG enzyme immunoassay. Overall VZV seroprevalence was 80.9% and it showed a significant increase by age, confirming a considerable circulation of VZV also in the older age groups not commonly considered at high risk. This study further supports the importance of vaccinating susceptible adolescents and women of childbearing age in order to reduce both maternal and foetal complications associated with varicella in pregnancy.

Varicella seroprevalence in Turkish population in Cyprus

AIM

This study was conducted to determine the age-specific seroprevalence of varicella zoster virus (VZV) infection in Turkish population in Cyprus.

METHODS

A total of 600 unvaccinated individuals aged 1-30 years were selected for the study with cluster sampling. Information on socio-demographic characteristics was gathered for each participant and, anti-VZV antibodies were assayed by using enzyme immune assay.

RESULTS

Of the 578 assayed samples, 486 (84.1%) were seropositive. Varicella seroprevalence increased sharply with age from 25% for the 2-3 year olds to 55, 78 and 85% for 4-5, 6-7 and 8-9 year olds, respectively. More than 90% of individuals >16 years of age were seropositive. Varicella seroprevalence was higher in large families with five and more members (91.2%) than in small families with four or fewer members (80.2%).

CONCLUSION

The majority of varicella-zoster virus infections occur during preschool period and at the first years of schooling. Therefore, routine varicella vaccination of children would be logical in Northern Cyprus, as is currently recommended by the European Working Group on Varicella.

Seroprevalence of varicella antibodies among pregnant women in Lyon-France

The purpose of the study was to calculate the seroprevalence of immunity to the varicella-zoster virus (VZV) infection and to evaluate the positive predictive value (PPV) and the negative predictive value (NPV) of the self-reported history of VZV infection in pregnant women. A cross sectional study was conducted in 18 private medical analysis laboratories. Information on socio-demographic characteristics and past history of varicella or zoster were collected using a questionnaire. Blood samples were obtained to determine the serological levels of past exposure to VZV. Overall, 486 pregnant women were recruited. The seroprevalence of VZV antibodies was 98.8%. Six women were seronegative, of whom four were primiparous. The PPV was high (99.5%) while the NPV was only 10.3%. The PPV is a reliable marker of prior VZV infection. In contrast, a negative history does not predict lack of immunity and should be completed by serological analysis which might be introduced to routine antenatal blood tests.

Parent-dependent barriers to varicella immunization in Israel: the importance of adequate information

AIM

To examine the parent-dependent barriers to varicella immunization in Israel.

METHODS

Data were collected by questionnaire from parents of children aged 1 to 18 years who attended an outpatient paediatric centre in five cities in Israel from March to May 2003.

RESULTS

A total of 1474 parents completed the questionnaire. A history of chicken pox was reported in 850 children (57.8%), mostly (83%) between ages 1-6 years. Of the 624 children without a history of chicken pox, 213 (34.1%) were immunized against varicella. Immunization rates were significantly lower in families with lower parental education and in patients from cities with a lower socioeconomic ranking (p < 0.05). The main reasons for not being vaccinated (49%) were related to insufficient information about the vaccine itself and the vaccination process. These reasons were more common in families with lower parental education and from cities with lower socioeconomic ranking (p < 0.01). Other reasons included fear of adverse effects (12%) and waning immunity (6%), preference of natural illness over immunization (12%), and financial limitations (5%).

CONCLUSIONS

Promoting parental knowledge about the varicella vaccine appears to be a key factor in improving the immunization rate, especially in families of lower education, and from cities with low socioeconomic ranking.

Changes in seroprevalence to four herpesviruses over 30 years in Swedish children aged 9–12 years

BACKGROUND

Changing social conditions and life-styles in Sweden may have affected the spread of varicella-zoster virus (VZV), herpes simplex virus (HSV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV).

OBJECTIVES

To study possible changes over 30 years in prevalence of antibodies against VZV, HSV, CMV, and EBV in Swedish children, using modern serological methods.

STUDY DESIGN

Serum samples from 819 Swedish children who were 9-12 years old in 1967-1968, in 1977-1978 (two cohorts), and in 1997, respectively, were examined. IgG antibodies against VZV, HSV, and CMV were measured by well validated enzyme-linked immunosorbent assays and against EBV by indirect immunoflourescense.

RESULTS

The seropositivity for VZV for 9-12 years old children was 50% in 1967-1968, 74-82% in 1977-1978, and 98% in 1997. The corresponding figures were 31%, 53%, 50%, and 58% for CMV, 35%, 35%, 32%, and 38% for HSV, and 64% in 1967-1968 and in 1977-1978 (both cohorts), and 62% in 1997 for EBV.

CONCLUSIONS

The seroprevalence for VZV increased significantly from 1967-1968 to 1997, and there was also a significant but smaller increase in the CMV seroprevalence, while seroprevalence to HSV and EBV remained relatively stable.

European seroepidemiology network 2: Standardisation of assays for seroepidemiology of varicella zoster virus

BACKGROUND

The aim of the European Sero-Epidemiology Network (ESEN2) is to harmonise the serological surveillance of vaccine-preventable diseases in Europe.

OBJECTIVE

To allow comparison of antibody prevalence in different countries by standardising results into common units.

STUDY DESIGN

For varicella zoster virus (VZV), a reference laboratory established a panel of 148 samples, characterised by indirect enzyme-immunoassay (ELISA), indirect immunofluorescence, and complement fixation test. Fifty-seven samples were also studied by the fluorescence antibody to membrane antigen test. The geometric mean of the antibody activity (GMAA) obtained from four ELISA determinations was used to characterise each sample of the panel as positive (GMAA: >100 mIU/ml), equivocal (GMAA: 50-100 mIU/ml) or negative (GMAA: <50 mIU/ml) for antibody to VZV (anti-VZV). Thirteen laboratories, using five different ELISA tests, tested the panel.

RESULTS

Agreement with the reference laboratory was above 85% in all cases, and the R(2) values obtained from regression analysis of the quantitative results were always higher than 0.87. Finally, the regression equations could be used to convert national values into a common unitage.

CONCLUSION

This study confirmed that results for anti-VZV obtained by different ELISA methods can be converted into common units, enabling the comparison of the seroprevalence profiles obtained in the participant countries.

The epidemiology of varicella and herpes zoster in The Netherlands: implications for varicella zoster virus vaccination

We studied the epidemiology of varicella (chickenpox) and herpes zoster (shingles) in The Netherlands to assess the desirability to implement routine varicella zoster virus vaccination in The Netherlands. Data on seroprevalence of varicella zoster virus in the general population (1995-1996), consultations of general practitioners for varicella (2000-2002) and herpes zoster (1998-2001) and hospital admissions due to varicella (1994-2001) and herpes zoster (1994-2001) in The Netherlands were analysed. The seropositivity increased sharply with age from 18.4% for both 0- and 1-year-olds, to 48.9%, 59.0%, 75.7% and 93.0% for 2-, 3-, 4- and 5-year-olds, respectively, and varied between 97.5% and 100% for older age groups. The average annual incidence of GP-consultations amounted to 253.5 and 325.0 per 100,000 for varicella and herpes zoster, respectively. The incidence of hospital admission due to varicella and herpes zoster was 1.3 (2.3 including side diagnosis) and 2.7 (5.8) per 100,000, respectively. Whilst for varicella, the incidence of GP-consultations and hospital admissions were highest in childhood, for herpes zoster, these were highest in elderly. Insight into epidemiology of varicella zoster is needed for the assessment of the desirability of introduction of routine varicella zoster vaccination.

Cost-effectiveness of varicella vaccination of healthcare workers

OBJECTIVE

Although transmission of VZV is recognized as an important cause for morbidity in health care workers (HCWs), there is no general agreement on the recommended immunization policy. This study aimed to evaluate several of such prevention policies in economic terms.

SETTINGS

Analysis of the cost per avoided future varicella cases among HCWs in Israel.

METHODS

A cost-effectiveness analysis was performed by comparing the cost per avoided case of varicella among a theoretical cohort of 63,353 physician and nurses aged less than 45 years in Israel. Four policies were examined: (a) do nothing (status quo); (b) vaccination of susceptible workers using VZV serotesting; with (c) or without anamnestic history of chickenpox; and (d) presumptive mass vaccination of all eligible workers. A Markov-based model was developed using data from our recent seroepidemiological study in target population and from the literature.

RESULTS

Screening and vaccination of susceptible workers using anamnestic selection is expected to reduce future cases, within 20 years since vaccination, from 58.3 to 33.0 with an incremental cost of 23,713 US dollars per avoided cases. Using only serological tests to detect susceptible workers would prevent additional 5.7 cases with an incremental cost of 206,692 US dollars per avoided case. Vaccinating all HCWs without serotesting, raises the costs markedly, with almost identical effectiveness, resulting in an incremental cost of 10.4 million US dollars per avoided case. Sensitivity analyses do not alter the ranking of the options.

CONCLUSION

From the employer's perspective, routine varicella vaccination program for HCWs with or without selection of susceptible workers is extremely expensive compared to other high-cost practiced approaches. Substantial reduction in cost of vaccination may alter this conclusion.

[Varicella-zoster virus seroprevalence in nursery and day-care workers in Lyon (France)]

OBJECTIVE

Varicella is a potential occupational hazard for susceptible individuals working in pediatric institutions because infected adults run a greater risk of severe or even fatal varicella and because the disease is so common in children and so contagious. The seroprevalence of varicella-zoster virus (VZV) was examined in a sample of day-care workers in Lyon (France) to determine whether a targeted vaccination policy was needed.

METHODS

Two hundred forty-one sera were sampled and analysed with an Elisa test between March and May 2001. Histories of past VZV infection were collected via questionnaires documented either before or after consultation of medical records or other sources of information.

RESULTS

The overall VZV seroprevalence was 99.6%. The positive predictive values of past varicella histories (documented or not) were>99% showing that a history of previous varicella in day-care workers was reliable. However, only 68 to 71% of these with serologically confirmed varicella reported a prior history of varicella. All subjects reporting a non-positive history of varicella were seropositive.

CONCLUSIONS

Virtually all day-care workers enrolled in this study presented serological evidence of VZV so that sub-populations at risk for varicella infection for which VZV vaccination may be effective could not be identified. However, the VZV seroprevalence of the workers in pediatric institutions being presumably higher than that of the general adult population (94-96.3%), vaccination of susceptible young recruits before any exposure to the VZV, or even vaccination of students willing to work in a pediatric institution, may be positive.

Seroepidemiology of varicella-zoster virus infection in a cosmopolitan city (Erzurum) in the eastern Turkey

OBJECTIVE

The aim of the study was to determine VZV seroprevalence under age 30 and to identify the relationship of VZV seroprevalence and several sociodemographic characteristics of the study subjects. The results were presented in order to design a strategy for vaccination against varicella-zoster virus (VZV).

MATERIAL AND METHOD

It was planned to include a total of 568 subjects. The sampling method of 30 clusters recommended for field studies was used for selecting subjects of a predetermined number in the rural and urban areas in eastern Turkey. ELISA method was used to examine the blood samples for VZV seropositivity. Age, gender, place of living, educational level, family size and socioeconomic status was investigated in the study subjects.

RESULTS

Positive VZV seroprevalence was detected in 78% of 559 subjects. Seroprevalence increased with age. Seroprevalence was 16.67% at the age of 1 year, subsequently increased to 57.58% at the age of 4 years, 70% at the age of 7 years, 92.31% at the age of 10 years and then remained 86.78-96.36% in subjects over the age of 10 years. No association was found between sociodemographic variables studied and prevalence levels of antibodies except for educational level in the 0-14 year group.

CONCLUSION

These results suggest that the majority of VZV infections occur during the early childhood; the best option to reduce the circulation of wild type VZV in the population would be the immunization of young children. VZV vaccine should be introduced into the routine childhood vaccination programme in Turkey.

Prevalence of IgG varicella zoster virus antibodies in the Kuikuro and Kaiabi indigenous communities in Xingu National Park, Brazil, before varicella vaccination

The purpose of the study was to estimate the prevalence of IgG antibodies against varicella zoster virus (VZV) in the two most populated indigenous ethnic groups from Xingu Indigenous National Park, in Brazil, prior to the introduction of vaccination against the disease, and to determine the positive and the negative predictive values of a history of varicella infection. In 2001, 589 inhabitants of two Kuikuro villages and three Kaiabi villages were evaluated and provided information concerning previous varicella infection. An indirect immunosorbent assay (ELISA) to detect IgG anti-VZV antibodies was performed in 224 blood samples - volunteer selection had no interference of anamnesis. IgG prevalence was 80.8% (95% Confidence Interval: 76% - 86%). The seroepidemiology of varicella in Xingu National Park prior to varicella vaccine introduction was comparable to the Brazilian national seroprevalence described in the literature, and so were the positive (98%) and the negative predictive value (41%) of the referred history.

Varicella seroprevalence and molecular epidemiology of varicella-zoster virus in Argentina, 2002

There is limited data on immunity against varicella-zoster virus (VZV) in adults in different parts of Argentina, and it is not known which VZV strains are circulating in Argentina. The objectives of this study were as follows: (i) to evaluate seroprevalence of varicella among adults, assessing the accuracy of clinical history and determining the sociodemographic factors associated with seropositivity; and (ii) to determine the VZV strains circulating in Argentina. A cross-sectional serological survey enrolling 2,807 women aged 15 to 49 years attending public health-care settings in four cities in Argentina (i.e., Buenos Aires, Salta, Mendoza, and Rosario) and one rural area was conducted from August to November 2002. Specimens for identification of VZV strains were obtained from vesicular lesions from 13 pediatric patients with varicella from different areas of the country. PCR amplification was used for genotyping. The overall seroprevalence of varicella antibodies was 98.5% (95% confidence interval, 98.0 to 98.9), ranging from 97.2% in central Buenos Aires to 99.3% in southern Buenos Aires and Salta. Varicella seroprevalence increased with age. Crowding and length of residence in the same place were associated with seropositivity. The positive predictive value of varicella history for immunity to varicella was 99.4%; however, the negative predictive value was 2.5%. The European genotype was identified in all viral specimens. In Argentina, seroprevalence in women more than 15 years old was high regardless of the area of residence. Negative or uncertain varicella history was not a good predictor of immunity. VZV genotype was stable in all areas of the country.

Seroprevalence of varicella antibodies in healthcare workers and health sciences students

The objective of this study was to assess the seroprevalence of varicella antibodies in healthcare workers and students of healthcare professions and to determine the validity of the self-reported varicella history for detecting susceptible subjects. Personnel of a general hospital and students were recruited and a 5 mL blood sample was obtained from all participants. A case report form, including previous self-reported history of varicella, was completed. A total of 91 healthcare workers (mean age, 30.6 years; S.D., 4.0; range, 23-40) and 92 students (mean age, 19.8 years; S.D., 2.5; range, 18-25) were recruited. The prevalence of varicella antibodies was 91.2% in healthcare workers and 92.1% in students. Overall, the sensitivity, specificity, positive and negative predictive values of a self-reported history of varicella were 68.4%, 66.7%, 95.4% and 17.2%, respectively. The preferred approach in these groups at risk of varicella will be to undergo serologic testing before immunization in those with negative or unknown history of varicella.

Screening healthcare workers for varicella-zoster virus: can we trust the history?

OBJECTIVE

To determine the relationship between immunity and a history of chickenpox based on a self-administered questionnaire.

METHODS

We investigated immunity to varicella-zoster virus in a cohort of newly recruited employees with different job categories and different nationalities using enzyme-linked immunosorbent assay IgG.

RESULTS

There were 1,058 new recruits. Of these, 890 (84%) were immune and 168 (16%) were susceptible. The susceptibility rate was 23% (n = 77) for Asian, 15% (n = 14) for South African, 13% (n = 66) for Middle Eastern, and 9% (n = 11) for Western employees. Physicians were more likely to be immune (93%) than were nurses (85%), medical technicians (75%), or administrative clerks (84%). Seropositivity was not affected by age or gender. The positive predictive value of a history of chickenpox for the seropositivity was 89% (511 of 574); the negative predictive value was 22% (105 of 484). History of chickenpox had a sensitivity of 57% (511 of 890) and a specificity of 63% (105 of 168).

CONCLUSIONS

The varicella-zoster virus seroprevalence among new employees was low, posing an important risk to existing employees and patients. Positive or negative history of chickenpox was an unreliable indicator of susceptibility among healthcare workers of different nationalities. Serologic screening of all employees and vaccination of those susceptible was recommended.

Immunofluorescence test for sensitive detection of varicella-zoster virus-specific IgG: an alternative to fluorescent antibody to membrane antigen test

A highly sensitive indirect fluorescence antibody test (IFAT) has been developed on the basis of varicella-zoster virus (VZV)-infected human lung carcinoma (A549) cells and evaluated for the determination of immunity to VZV. Different serum panels with negative, low, moderate or high anti-VZV IgG levels detected by the fluorescent antibody to membrane antigen (FAMA) assay were investigated. As a result, the sensitivity and the specificity of IFAT were 100% compared to FAMA test. In anti-VZV IgG-positive sera, a significant correlation between the results of FAMA procedure and IFAT could be shown. However, there were considerably higher antibody titers by the IFAT than by FAMA. Whereas the FAMA test had a detection limit of 250 mIU/ml anti-VZV IgG, the limit of detection of IFAT was 50 mIU/ml. In conclusion, the IFAT using VZV-infected A549 cells as antigen allows a highly sensitive, specific, and rapid detection of anti-VZV IgG class antibodies. This simple technique can replace the labor-intensive FAMA procedure for laboratory determination of immunity to VZV.

Consensus: varicella vaccination of healthy children--a challenge for Europe

The seriousness of varicella-zoster virus (VZV) infection as a public health issue is becoming clearer as country-specific epidemiologic and pharmacoeconomic data become available. In Germany, for example, studies have shown that >5.5% of immunologically healthy individuals develop varicella-related complications such as bacterial superinfections, acute neurologic disorders, pneumonia, bronchitis and otitis media; whereas in Italy, 3.5 to 5% of childhood cases of varicella cause complications such as upper respiratory tract and cutaneous infections. Varicella vaccines are now available. These live attenuated Oka strain vaccines have been shown in extensive studies to be highly immunogenic and well-tolerated in immunocompetent and immunocompromised children, with seroconversion rates ranging from 94 to 100% and 53 to 100%, respectively. These vaccines are also highly effective against clinical disease. These considerations led to a reevaluation of varicella vaccination policies. A routine varicella vaccination program targeting healthy children has already been implemented in the US, and data produced are encouraging and valuable. Similar strategies have not yet been adopted across Europe. The European Working Group on Varicella (EuroVar) was formed in 1998 to address the issues surrounding varicella epidemiology in Europe. After a series of meetings, the EuroVar members prepared a consensus statement recommending routine varicella vaccination for all healthy children between 12 and 18 months and to all susceptible children before their 13th birthday, in addition to catch-up vaccination in older children and adults who have no reliable history of varicella and who are at high risk of transmission and exposure. However, such a policy is recommended only if a very high coverage rate can be achieved. This could be reached with a measles-mumps-rubella-varicella combined vaccine.

[Prevalence of varicella-zoster virus antibodies in young adults from different Brazilian climatic regions]

To evaluate the prevalence of varicella-zoster virus infection in young adults from different Brazilian urban regions, 975 serum samples from blood donors aged 20 to 29 years, from tropical climate cities (Salvador and Fortaleza) and from temperate climate cities (S o Paulo, Curitiba and Porto Alegre) were tested by an in-house ELISA for detection of anti-varicella-zoster virus IgG antibodies. The overall prevalence was 94.2%. The lowest rate was observed in Fortaleza (88.7%) and the highest in Curitiba (99.5%). Seroprevalence in tropical regions of Brazil (89.4%) was significantly higher than in temperate regions (97.3%), a similar pattern to that observed in other tropical countries.

Epidemiology of primary varicella hospitalizations in Spain

An approach to the burden of varicella can be obtained from information on the hospitalizations. Data were obtained from the national surveillance system for hospital data. All hospital discharges for varicella were analyzed for the 1995-1998 period. A total of 3632 primary varicella-related discharges were identified, representing an annual incidence of 2.8 per 100,000 population. A total of 58% of cases were <10 years of age and 33% were 21-50 years old. Each year primary varicella will be responsible for 6174 days of hospitalization, representing an annual cost of 1.6 million euros. There is substantial severe morbidity each year from varicella that, to reduce, would require vaccination of infants and susceptible adults.

Seroprevalence of varicella-zoster virus in the German population

The present study was conducted to generate data on the epidemiology of varicella-zoster virus (VZV) infections in Germany as a basis for health economic evaluations of varicella vaccination strategies. The survey was designed as a cross-sectional, age-stratified study of the VZV seroprevalence in the German population. The status of immunity of 4602 individuals a aged 0 to >70 years was investigated by means of an indirect enzyme immunoassay and the fluorescent antibody to membrane assay. After waning of maternal antibodies over the period of 6-9 months seropositivity rates remained low by the end of the 1st year of life. By the age of 4-5 years 62.5% (95% CI; 56.0-68.5) of the pre-school children had already been infected with VZV and at the age of 10-11 years 94.2% (95% CI; 91.0-96.0) of children were positive for anti-VZV antibodies. Among the age-group of >40 years old, only few individuals were susceptible for VZV. The median antibody levels to VZV did not significantly decline with increasing age. In comparison with figures of previous studies the age-specific seroprevalence data presented here do not provide evidence for an upward shift in the age distribution of varicella in Germany. Since the majority of VZV infections occurs during the early childhood, the best option to reduce the circulation of wild-type VZV in the population would be the immunization of young children.

Seroprevalence of varicella-zoster virus immunoglobulin G antibodies in Swiss adolescents and risk factor analysis for seronegativity

BACKGROUND

Little is known about the seroprevalence of anti-varicella-zoster virus (VZV) serum antibodies in adolescents in Switzerland as in most other European countries.

METHODS

Serum specimens from 13- to 15-year-old students from eight urban and rural areas in Switzerland, obtained as part of an allergy risk assessment study project (SCARPOL), were available for analysis of IgG antibodies against VZV by enzyme-linked immunosorbent assay (ELISA) and confirmation by fluorescent antibody staining of membrane antigen in a subcohort. Serum specimens and comprehensive sociodemographic data had been collected during two study periods between 1992 and 1995.

RESULTS

Data and serum specimens were available from 1709 and 1788 subjects, respectively. Seroprevalence of anti-VZV antibodies as measured by ELISA was 95.5% (95% confidence interval, 94.5 to 96.4). When serum specimens that were indeterminate by ELISA were tested by FAMA, seroprevalence was 96.5% (95% confidence interval, 95.7 to 97.4). After logistic regression analysis, the number of siblings was the only factor that significantly influenced the presence of VZV antibodies (90.1% in those with no siblings, >96% with 1 or more siblings), whereas residence (urban vs. rural), parental education, nationality and gender did not.

CONCLUSIONS

Seroprevalence of anti-VZV serum antibodies is comparatively high among Swiss adolescents. Individuals who grow up without siblings have a significant risk of evading natural VZV infection in childhood, and they therefore form a potential target group for varicella immunization in Switzerland.