The seroepidemiology and transmission dynamics of varicella in Australia

Measles, mumps, rubella and varicella antibodies among international and domestic university students

BACKGROUND

Vaccine-preventable infections are generally well controlled in Australia. However, gaps in immunity can lead to outbreaks and are important to identify. Young adults are a highly mobile population and a potential source of imported infections. We aimed to evaluate anti- measles, mumps, rubella and varicella (MMR&V) IgG seroprevalence and explore factors relating to antibody seropositivity.

METHODS

A cross-sectional online survey was conducted among students from a large Australian university to collect demographic, vaccination, infection and travel characteristics. Blood samples were collected to measure MMR&V seroprevalence. Logistic regression was used to identify factors associated with seropositivity.

RESULTS

Among 804 university students, seroprevalence (positive or equivocal) for measles was 82.3% (95% CI 79.6-84.8%), mumps 79.5% (95% CI 76.7-82.3%), rubella 91.5% (95% CI 89.6-93.5%) and varicella 86.2% (95% CI 84.1-88.8%), with 452 (56.2%, 95% CI 52.8-59.6) seropositive to all four viruses. Varicella seropositivity was highest in the older birth cohort (born 1988-1991). Measles seropositivity was higher for international students compared to domestic students. Among international students, mumps seroprevalence was significantly lower than measles and rubella seroprevalence. International travel in the previous 12 months was reported by 63.1% of students, but only 18.2% of travellers reported seeking pre-travel health advice prior to most recent international travel.

CONCLUSIONS

Overall, this study suggests immunity to MMR&V is sub-optimal. We found the university student population to be highly mobile and unlikely to seek pre-travel advice; thus, they are a potential source of infection importation. The implementation of university immunization policies could address the gaps identified and our findings can inform the development of targeted vaccination campaigns.

Active prospective national surveillance for congenital and neonatal varicella in Australia shows potential prevention opportunities

To compare the incidence and outcomes of congenital and neonatal varicella in Australia in the pre-vaccination (1995-1997) and post-vaccination era (after 2005 to November 2020), active prospective national surveillance for congenital varicella syndrome (CVS) and neonatal varicella infection (NVI) was conducted through the Australian Paediatric Surveillance Unit (APSU). Compared with 1995-1997, there was a 91.5% reduction in the incidence of CVS and a 91.3% reduction in the incidence of NVI in 2009-2020. However, almost half of the mothers in 2009-2020 were born overseas and came from countries without a vaccination program. Although there has been a substantial and sustained decrease in the reported incidence of CVS and NVI in Australia since 2006, congenital and neonatal varicella infections persist. Thus, there is an opportunity for targeted screening of varicella in young migrant, asylum seeker and refugee women at risk of varicella infection and prioritisation for vaccination to prevent CVS and NVI.

Herpes zoster vaccination in Australia: what's available and who benefits?

Acute herpes zoster and associated postherpetic neuralgia is caused by reactivation of latent varicella zoster virus. It can be debilitating for older adults and interfere with activities of daily living

A live, attenuated single-dose vaccine, that protects against both acute herpes zoster and postherpetic neuralgia, is available for free to all Australians aged 70 years, and in a catch-up program for those aged 71–79 years

The vaccine is contraindicated in people who are immunocompromised, but can be considered in those who are receiving low doses of selected disease-modifying antirheumatic drugs

Records of the Australian Immunisation Register suggest that only a third of 70 year olds received the vaccine in the first year-and-a-half of the program. This is likely an underestimation, but emphasises the importance of ensuring the vaccine is offered to all eligible patients and that vaccination is recorded on the Register

A non-live recombinant herpes zoster vaccine has recently been developed which is more efficacious than the live vaccine in clinical trials. It is registered in Australia but not currently available

Burden of varicella in the Asia-Pacific region: a systematic literature review

INTRODUCTION

Varicella is a highly contagious infection that can lead to serious complications, particularly in high-risk groups; however, it is vaccine preventable. Disease awareness and understanding of the disease burden can strongly influence vaccine coverage. This review provides insight into the current epidemiology and the importance of varicella from both public health and economic perspectives across the Asia-Pacific (APAC) region. Areas covered: A systematic literature review was conducted to identify studies on the incidence, seroprevalence, fatality rate and complication rate of varicella. Economic burden studies were also captured. Altogether, 125 studies were identified across the region; these were supplemented by government reports (gray data). Reported vaccine coverage varied from 2.8% to 97%; a key influencing factor was inclusion of the varicella vaccine in national immunization programs. In general, varicella incidence in the unvaccinated population was highest in children ≤5 years old and seroprevalence increased with age. Economic analyses highlighted the cost-saving potential of vaccination programs, especially from a societal perspective. Expert opinion: Varicella-related data varied greatly across the APAC region, highlighting the need to better understand the burden of varicella in this area, and particularly identified the need for better surveillance and reporting.

Epidemic Varicella Zoster Virus among University Students, India

We investigated a yearlong varicella zoster virus outbreak in a highly susceptible young adult population at a large university in India. Outbreaks of varicella infection among adults are not well described in the literature. Infection control measures and vaccination policy for this age group and setting are needed.

The changing epidemiology of varicella and herpes zoster in Hong Kong before universal varicella vaccination in 2014

In Hong Kong, universal varicella vaccination started in July 2014. Before this, children could receive varicella vaccine via the private market. We analysed the epidemiology of varicella and zoster before universal vaccination. We estimated varicella vaccination coverage through surveys in preschool children. We estimated the burden of varicella and zoster with varicella notifications from 1999/00 to 2013/14, Accident and Emergency Department (A&E) attendance and inpatient admissions to public hospitals from 2004/05 to 2013/14. We fitted a catalytic model to serological data on antibodies against varicella-zoster virus to estimate the force of infection. We found that varicella vaccination coverage gradually increased to about 50% before programme inception. In children younger than 5 years, the annual rate of varicella notifications, varicella admission and zoster A&E attendance generally declined. The annual notification, A&E attendance and hospitalisation rate of varicella and zoster generally increased for individuals between 10 and 59 years old. Varicella serology indicated an age shift during the study period towards a higher proportion of infections in slightly older individuals, but the change was most notable before vaccine licensure. In conclusion, we observed a shift in the burden of varicella to slightly older age groups with a corresponding increase in incidence but it cannot necessarily be attributed to private market vaccine coverage alone. Increasing varicella vaccination uptake in the private market might affect varicella transmission and epidemiology, but not to the level of interrupting transmission.

Use of pre-travel vaccine-preventable disease serology as a screening tool to identify patients in need of pre-travel vaccination: a retrospective audit

BACKGROUND

Vaccination is a safe and effective public health intervention that not only protects individual travellers from vaccine-preventable diseases (VPDs), but prevents them from becoming a source of disease in their destination and on their return. Obtaining an accurate vaccination history from travellers during a pre-travel review can be difficult; serology may be used to identify patients who are non-immune to specific diseases in order to guide vaccination requirements. Clinically relevant data about the usefulness of serology in this setting are lacking. We performed a retrospective audit of pre-travel VPD serology requested by practitioners of a busy community-based travel clinic.

METHODS

All serological results for measles, mumps, rubella, varicella zoster virus, hepatitis A and B requested over a 5-year period were extracted and analysed. Results were stratified by gender and year of birth and compared using Stata.

RESULTS

Four thousand four hundred and fifty-one serological assays from 1445 individual were assessed. Overall, 47% of patients tested had at least one negative serological result. High rates of seropositivity for measles, mumps and rubella were seen in those born prior to 1966 but >10% of travellers born after 1966 lacked serological evidence of protection against these diseases. Hepatitis A and B serological results revealed broadly lower rates of immunity in our community likely reflecting the absence of these vaccines from historical vaccine protocols.

CONCLUSIONS

Serology can be a useful tool in the identification of non-immune travellers to enable targeted vaccination prior to travel. We recommend that travel health clinicians assess patients' vaccination and infection histories, and strongly consider serology or vaccination where there is doubt about immunity. This will help protect the traveller and prevent importation of disease into destination or home communities.

Looking back to move forward: a twenty-year audit of herpes zoster in Asia-Pacific

Background

Herpes zoster (HZ) is a prevalent viral disease that inflicts substantial morbidity and associated healthcare and socioeconomic burdens. Current treatments are not fully effective, especially among the most vulnerable patients. Although widely recommended, vaccination against HZ is not routine; barriers in Asia-Pacific include long-standing neglect of adult immunisation and sparse local data. To address knowledge gaps, raise awareness, and disseminate best practice, we reviewed recent data and guidelines on HZ from the Asia-Pacific region.

Methods

We searched PubMed, Scopus, and World Health Organization databases for articles about HZ published from 1994 to 2014 by authors from Australia, China, Hong Kong, India, Indonesia, Japan, Korea, Malaysia, New Zealand, the Philippines, Singapore, Taiwan, Thailand, and Vietnam. We selected articles about epidemiology, burden, complications, comorbidities, management, prevention, and recommendations/guidelines. Internet searches retrieved additional HZ immunisation guidelines.

Results

From 4007 retrieved articles, we screened-out 1501 duplicates and excluded 1264 extraneous articles, leaving 1242 unique articles. We found guidelines on adult immunisation from Australia, India, Indonesia, Malaysia, New Zealand, the Philippines, South Korea, and Thailand.

HZ epidemiology in Asia-Pacific is similar to elsewhere; incidence rises with age and peaks at around 70 years – lifetime risk is approximately one-third. Average incidence of 3–10/1000 person-years is rising at around 5% per year. The principal risk factors are immunosenescence and immunosuppression. HZ almost always causes pain, and post-herpetic neuralgia is its most common complication. Half or more of hospitalised HZ patients have post-herpetic neuralgia, secondary infections, or inflammatory sequelae that are occasionally fatal. These disease burdens severely diminish patients’ quality of life and incur heavy healthcare utilisation.

Conclusions

Several countries have abundant data on HZ, but others, especially in South-East Asia, very few. However, Asia-Pacific countries generally lack data on HZ vaccine safety, efficacy and cost-effectiveness. Physicians treating HZ and its complications in Asia-Pacific face familiar challenges but, with a vast aged population, Asia bears a unique and growing burden of disease. Given the strong rationale for prevention, most adult immunisation guidelines include HZ vaccine, yet it remains underused. We urge all stakeholders to give higher priority to adult immunisation in general and HZ in particular.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2198-y) contains supplementary material, which is available to authorized users.

Evaluation of a vaccination strategy by serosurveillance data: The case of varicella

Serological studies have many important epidemiologic applications. They can be used to investigate acquisition of various infections in different populations, measure the induction of an immune response in the host, evaluate the persistence of antibody, identify appropriate target groups and the age for vaccination. Serological studies can also be used to determine the vaccine efficacy. Since 1995 a varicella vaccine is available and it has been recommended in several countries (e.g. USA, Australia, Canada, Costa Rica, Ecuador, etc.). Nevertheless few varicella seroprevalence studies in countries that adopted an URV are available. It is related to the relatively recent introduction of the vaccination and to the lack of structured and collaborative surveillance systems based on serosurvey at national or regional level. Varicella seroprevalence data collected before the introduction of vaccination strategies allowed to establish the age of vaccination (e.g., indicated the opportunity to offer the vaccine to Italian susceptible adolescents). In the post-vaccination era, seroprevalence data demonstrated vaccine as immunogenic and excluded an increase of the age of infection linked to the vaccination strategy. New seroprevalence studies should be performed to answer to open questions, such as the long-term immunity and the change of the herpes zoster epidemiological pattern related to the vaccine.

Parental Attitudes and Factors Associated With Varicella Vaccination in Preschool and Schoolchildren in Hong Kong: A Cross-Sectional Study

This study investigates parental attitudes and factors associated with varicella vaccination among preschool and schoolchildren prior to introduction of the vaccine into Hong Kong's universal Childhood Immunization Program.Fourteen kindergartens and 5 primary schools in Hong Kong were randomly selected in 2013. Parents of the students were invited to answer the self-administered questionnaires. Acquired information included demographic characteristics and socioeconomic statuses of families, children's history of chickenpox infection and vaccination, and reasons for getting children vaccinated. Logistic regression was applied to examine the factors associated with vaccination.From the 3484 completed questionnaires, the calculated rates of varicella infection and vaccination were 20.7% and 69.0%, respectively. Barriers to vaccination included parental uncertainties about vaccine effectiveness, lack of recommendation from the government, and concerns on adverse effects. Overall, 71.8%, 69.0%, and 45.7% of the parents rated family doctors, specialists, and the government, respectively, as very important motivators of vaccination. Higher parental educational level and family income, better perceived knowledge of varicella and chance of infection, discussion with a family doctor, and positive health belief towards vaccination were associated with vaccination (all P < 0.05).The rate of vaccination in Hong Kong was higher than that of some other countries that also did not include the vaccine in their routine immunization programs. More positive parental attitudes, higher socioeconomic status, and discussion with a family doctor are associated with greater vaccination rates. The important roles that health professionals and the government play in promoting varicella vaccination were emphasized.

Control of varicella in the post-vaccination era in Australia: a model-based assessment of catch-up and infant vaccination strategies for the future

In Australia, varicella vaccine was universally funded in late 2005 as a single dose at 18 months. A school-based catch-up programme for children aged 10-13 years without a history of infection or vaccination was funded until 2015, when those eligible for universal infant vaccination would have reached the age of high school entry. This study projects the impact of discontinuing catch-up vaccination on varicella and zoster incidence and morbidity using a transmission dynamic model, in comparison with alternative policy options, including two-dose strategies. At current vaccine coverage (83% at 2 years and 90% at 5 years), ceasing the adolescent catch-up programme in 2015 was projected to increase varicella-associated morbidity between 2035 and 2050 by 39%. Although two-dose infant programmes had the lowest estimated varicella morbidity, the incremental benefit from the second dose fell by 70% if first dose coverage increased from 83% to 95% by age 24 months. Overall zoster morbidity was predicted to rise after vaccination, but differences between strategies were small. Our results suggest that feasibility of one-dose coverage approaching 95% is an important consideration in estimating incremental benefit from a second dose of varicella vaccine.

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.

Seroepidemiology of varicella-zoster virus in Korea

This study was designed to assess the immune status of the Korean population against varicella-zoster virus (VZV) through a seroepidemiologic study. Residual blood samples were collected from diagnostic laboratories throughout Korea. Samples were collected in October 2009 to March 2010 from persons 0-79 yr of age and were tested by ELISA (Enzygnost®; Dade Behring, Schwalbach, Germany). Total seroprevalence in subjects 1-79 yr of age was 89.6%. Seroprevalence increased as age increased from 67.3% in subjects 1-4 yr of age to 94.2% in subjects 10-14 yr of age and in subjects over 20 yr of age seroprevalence ranged from 98.0% to 100%. In children under 1 yr of age, passive immunity waned after birth with none of the subjects having antibodies from 7 months of age and over. Among subjects 1-79 yr of age, susceptible subjects to VZV were mainly under 20 yr of age. These results provide information in understanding the dynamics of varicella disease in Korea, which is important in building up strategies for disease control.

Susceptibility to varicella-zoster among pregnant women in the province of Lecce, Italy

BACKGROUND

Varicella is predominantly a childhood disease, considered a mild self-limiting disease that can have serious complications for a pregnant woman and her developing fetus.

OBJECTIVES

We investigated the susceptibility to varicella-zoster Virus (VZV) among pregnant women in the province of Lecce.

STUDY DESIGN

A cross-sectional study was carried out in Departments of Gynecology and Obstetrics of the Province of Lecce, where 539 pregnant women were recruited, and face-to-face interviews were conducted. Varicella IgG tests were performed.

RESULTS

The prevalence of varicella susceptibility among pregnant mothers was 10.6%. The prevalence of IgG antibodies increases significantly with increasing age, from 62.5% in the age group 15-19 years to 94.4% in the age group 40-49 years.

DISCUSSION

In the Italian National Vaccination Plan 2005-2007, varicella vaccine is only recommended for childbearing women. A safe and effective vaccine is available and no abnormalities have been observed among infants born to susceptible women who received varicella vaccines during pregnancy. Such a high number of susceptible women indicates that preventive and informative programs should be introduced, even among those who do not plan to become pregnant. Routine counselling, varicella IgG antibody screening and varicella vaccination should be considered if they have no history of the infection, to reduce the risk of fetal complications and the cost of healthcare associated with the infection.

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.

Modelling the impact of one-dose vs. two-dose vaccination regimens on the epidemiology of varicella zoster virus in Australia

We examined the impact of one-dose vs. two-dose vaccination strategies on the epidemiology of varicella zoster virus (VZV) in Australia, using a mathematical model. Strategies were assessed in terms of varicella (natural and breakthrough) and zoster incidence, morbidity, average age of infection and vaccine effectiveness (VE). Our modelling results suggest that compared to a one-dose vaccination strategy (Australia's current vaccination schedule), a two-dose strategy is expected to not only produce less natural varicella cases (5% vs. 13% of pre-vaccination state, respectively) but also considerably fewer breakthrough varicella cases (only 11·4% of one-dose strategy). Therefore a two-dose infant vaccination programme would be a better long-term strategy for Australia.

Herpes zoster burden of illness and health care resource utilisation in the Australian population aged 50 years and older

Incidence of zoster and post-herpetic neuralgia (PHN) and associated health care resource utilisation were investigated in the Australian population aged > or =50 years, using general practice data from 2000 to 2006, and pharmaceutical prescribing, hospital morbidity and emergency department data from 1998 to 2005. Zoster and PHN incidence rates were estimated as approximately 10/1000 and 1.45/1000 persons, respectively, with antivirals prescribed for 73.5% of zoster cases. Estimated hospitalisation and emergency department visit rates were 0.67/1000 and 0.38/1000 persons, respectively. Management of zoster (including PHN) involved approximately 2.4 general practitioner consultations. Total costs to the health care system were estimated as approximately 32.8 million per year. The substantial burden of zoster and PHN highlights the potential benefit of zoster vaccination.

Varicella vaccination in Australia and New Zealand

Varicella-zoster virus has been responsible for a significant disease burden, including hospitalizations and deaths in Australia and New Zealand. Varicella vaccine has been available in Australia since 1999 and, since November 2005, has been funded under the National Immunisation Program for use in all children as a single dose at 18 months of age and in a school-based catch-up program at 10-13 years of age. Recent hospitalization data from Australia show a decline in varicella hospitalizations in children 1-4 years of age, most likely related to vaccination. In New Zealand, varicella vaccine has been available since 1999 but is currently not recommended or funded on the New Zealand national immunization schedule. The anticipated licensure of combination measles-mumps-rubella-varicella vaccines in both countries may lead to future schedule changes.

National serosurvey of poliovirus immunity in Australia, 1996-99

OBJECTIVE

To measure immunity to poliovirus types 1, 2 and 3 in the Australian population.

METHODS

Sera were collected opportunistically from laboratories around Australia between 1996 and 1999. A representative sample by age and gender was tested for neutralising antibodies to poliovirus types 1, 2 and 3. A titre of > or = 8 was considered antibody positive and indicative of immunity.

RESULTS

Of the 1,813 sera tested, 82% were antibody positive for poliovirus type 1 and 88% were positive for type 2. Immunity to type 3 poliovirus was lower overall (74%) and especially in school-aged children and young adults. For all three poliovirus types, there were more females immune than males and immunity peaked in the 2-4 years age group. The proportion of the population immune to all three types was 59%, and 3% were negative for all three types.

CONCLUSIONS AND IMPLICATIONS

This is the first national serosurvey for immunity to poliovirus in Australia. Herd immunity is probably sufficient to prevent generalised outbreaks due to type 1 and 2 poliovirus, but this may not be the case for type 3. However, localised outbreaks of any poliovirus type could still occur following reintroduction unless uniformly high levels of vaccination coverage are maintained. Ongoing serosurveillance is required following the recent change back to inactivated polio vaccine.

The comparative sero-epidemiology of varicella zoster virus in 11 countries in the European region

The European sero-epidemiology network (ESEN2) aims to standardise serological surveillance of varicella zoster virus (VZV) in 11 participant countries. In each country, serum banks were collected between 1996 and 2003 and tested for VZV antibodies. Assay results were standardised so that international comparisons could be made. Age-specific forces of infection were calculated for three age groups (<5, 5-9 and >or=10 years of age) and used to estimate the base reproduction number (R(0)) and the herd immunity threshold (H). Most VZV infection occurred in childhood, but there was a wide variation in transmissibility, with R(0) ranging from 16.9 in the Netherlands to 3.3 in Italy. Herd immunity thresholds varied from 70% in Italy to 94% in the Netherlands. There are substantial differences in VZV sero-epidemiology within the European region, which will need to be taken into account in designing national policies regarding VZV vaccination.

Incidence of cytomegalovirus infection among the general population and pregnant women in the United States

Background

Cytomegalovirus (CMV) is a common opportunistic infection among HIV-infected individuals, a major source of serious complications among organ-transplant recipients, and a leading cause of hearing loss, vision loss, and mental retardation among congenitally infected children. Women infected for the first time during pregnancy are especially likely to transmit CMV to their fetuses. More children suffer serious disabilities caused by congenital CMV than by several better-known childhood maladies such as Down syndrome or fetal alcohol syndrome

Methods

Using CMV seroprevalence data from the nationally representative Third National Health and Nutrition Examination Survey, we estimated CMV incidence among the general United States population and among pregnant women. We employed catalytic models that used age-specific CMV seroprevalences as cumulative markers of past infections in order to derive estimates of three basic parameters: the force of infection, the basic reproductive rate, and the average age of infection. Our main focus was the force of infection, an instantaneous per capita rate of acquisition of infection that approximates the incidence of infection in the seronegative population.

Results

Among the United States population ages 12–49 the force of infection was 1.6 infections per 100 susceptible persons per year (95% confidence interval: 1.2, 2.4). The associated basic reproductive rate of 1.7 indicates that, on average, an infected person transmits CMV to nearly two susceptible people. The average age of CMV infection was 28.6 years. Force of infection was significantly higher among non-Hispanic Blacks (5.7) and Mexican Americans (5.1) than among non-Hispanic Whites (1.4). Force of infection was significantly higher in the low household income group (3.5) than in the middle (2.1) and upper (1.5) household income groups. Based on these CMV incidence estimates, approximately 27,000 new CMV infections occur among seronegative pregnant women in the United States each year.

Conclusion

These thousands of CMV infections in pregnant women, along with the sharp racial/ethnic disparities in CMV incidence, are compelling reasons for accelerating research on vaccines and other interventions for preventing congenital CMV disease. Nevertheless, the relatively low force of infection provides encouraging evidence that modestly effective vaccines and rates of vaccination could significantly reduce CMV transmission.

Reliability of information on varicella history in preschool children

OBJECTIVE

To verify how reliable is the information provided by parents about the history of varicella in their children.

METHODS

204 parents of previously healthy children attending two municipal day-care centers of São Paulo city were interviewed between August 2003 and September 2005. A standardized form was filled out with information regarding age, sex, history of varicella and other diseases, drug use and antecedent of immunization, After medical history, physical examination and checking of immunization records, 5 ml of blood were collected for ELISA (in house) varicella test. Exclusion criteria were: age less than 1 year or more than 60 months, previous immunization against chickenpox, presence of co-morbidities or recent use of immunosuppressive drugs. Data were filed in a data bank using the Excel 2003 Microsoft Office Program and stored in a PC computer. The exact Fisher test was employed to calculate sensibility, specificity, positive and negative predictive values of history of varicella informed by children's parents.

RESULTS

The age of the children varied from 12 to 54 months (median, 26 months; 49 (24%) children had positive history of varicella, 155 (76%) a negative or doubtful history. The predictive positive and negative values of the information were 90% and 93%, respectively (p = 0.0001).

CONCLUSIONS

The degree of reliability of information about history of varicella informed by parents of children attending day care centers was high and useful to establish recommendations on varicella blocking immunization in day-care centers.

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.

Modelling the impact of vaccination on the epidemiology of varicella zoster virus in Australia

OBJECTIVE

To model the impact of universal varicella vaccination in Australia.

METHODS

The results of an Australia-wide serosurvey for varicella zoster virus (VZV) immunity were used to parameterise realistic, age-structured deterministic models (RAS) developed by Brisson and colleagues. We examined the impact of a vaccination program for one-year-olds alone, and with a catch-up campaign for 11-year-olds, on the incidence of varicella and zoster, using Australia's population structure. Morbidity was then determined by calculating the number of hospital in-patient days.

RESULTS

Infant vaccination is predicted to reduce the incidence of varicella. However, zoster incidence is expected to increase initially, assuming exposure to varicella boosts immunity to zoster. Accumulated morbidity from both varicella and zoster is predicted to remain above that expected without vaccination for the first 70 years of an infant program (assuming 90% coverage with boosting for 20 years). However, after 70 years the net health savings from vaccination are predicted to increase substantially.

CONCLUSIONS AND IMPLICATIONS

Infant vaccination is expected to be a successful long-term commitment to reducing morbidity associated with VZV infection in Australia.

Uptake of varicella vaccine—a cross sectional survey of parental attitudes to nationally recommended but unfunded varicella immunisation

The aim of this study was to assess the uptake of varicella vaccine in South Australian children under circumstances where varicella immunisation is recommended, but is not funded by Government. The study examined the main reasons that determined a parent's decision whether or not to have their child immunised with varicella vaccine. A cross-sectional survey was conducted by Computer Aided Telephone Interviews (CATI) in June 2004. Data were obtained from 613 households containing 1148 children aged from birth to 17 years of age. Statistical analyses were performed using data weighted to the South Australian population. Six hundred and eighty children (55.7%) had a history of varicella infection and 446 children (42.0%) had received varicella vaccine (weighted data). The most common reasons cited for not having children immunised included lack of knowledge about the vaccine and cost. One year after inclusion of varicella vaccine in the Australian Standard Vaccination Schedule there is evidence of incomplete coverage in children in South Australia due to absence of government funding for vaccine provision.

Varicella vaccination in Australia

Varicella zoster virus (VZV) causes both chickenpox and herpes zoster and is responsible for a significant disease burden, including hospitalizations and deaths, in Australian children and adults. Varicella vaccine has been available in Australia for 5 years; however, from November 2005, it will be funded for use in all susceptible children at 18 months and 10-13 years of age under the National Immunisation Program. Experience with universal varicella vaccination of children in the USA over the last 10 years has shown that the vaccine is safe and highly effective in reducing varicella-related disease. This review summarizes the epidemiology of VZV-related disease in Australia, the use of varicella vaccine and the international experience with vaccine efficacy and safety. The potential impact of varicella vaccination on the incidence of herpes zoster is also discussed.