Comparative seroepidemiology of pertussis, diphtheria and poliovirus antibodies in Singapore: waning pertussis immunity in a highly immunized population and the need for adolescent booster doses

Background

We assessed the seroepidemiology of pertussis, diphtheria and poliovirus antibodies in a cohort of highly immunized children, together with the burden of these diseases in Singapore.

Methods

Hospital residual sera collected between August 2008 and July 2010 from 1200 children aged 1–17 years were tested for the prevalence of IgG antibodies against Bordetella pertussis, diphtheria toxoid, and all three poliovirus types by enzyme-linked immunosorbent assays.

Results

We found an overall seroprevalence of 99.4% (95% CI 98.8–99.7%) for diphtheria, and 92.3% (95% CI 90.6–93.6%) for poliomyelitis, along with no indigenous cases of these diseases since 1993. However, the seroprevalence for pertussis was 60.8% (95% CI 58.0–63.5%) only. Among the subjects who had completed three doses of pertussis vaccination by the age of 2 years (n = 1092), the pertussis seroprevalence was 85.0% (95% CI 79.7–89.2%) in those who received the last vaccination within a year before the study, and it decreased to 75.0% (95% CI 64.5–83.2%) and 63.1% (95% CI 50.9–73.8%) in those who had the last vaccination 1 year and 2 years before the study, respectively. The seroprevalence remained at about 50% for those whose last pertussis vaccination was administered 4 years and longer before the study.

Conclusions

The high seroprevalence for poliomyelitis and diphtheria confer solid herd immunity to eliminate these diseases in Singapore. In contrast, immunity against pertussis waned considerably over time, and routine boosters should be given to adolescents to ensure sustained immunity against pertussis.     

Assessment of poliovirus antibody seroprevalence in polio high risk areas of West Africa

We conducted a serological survey of anti-polio antibodies in polio high-risk areas of Mali, Guinea and Cote d’Ivoire to assess risk of future poliovirus outbreaks.Random community sampling of children 6–11 and 36–48 months-old was conducted; neutralizing antibodies against poliovirus were detected using microneutralization assay.We analysed 1059/1064 (99.5%) of enrolled children. Seroprevalence to poliovirus type 1 (PV1) across all age groups and locations ranged between 92 and 100%, for PV2 it was 77–100%, and 89–95% for PV3. PV2 seroprevalence in the younger age group in Guinea and Cote d’Ivoire was <80%. History of <4 polio vaccine doses and acute malnutrition were associated with seronegativity (OR = 2.1 CI95% = 1.5–3.1, OR = 1.8 CI95% = 1.1–3.3 respectively).The risk of poliovirus outbreak following importation is low because of high population immunity to PV1, however, due to large cohort of PV2 seronegative children any future detection of vaccine-derived poliovirus type 2 requires urgent response to arrest rapid spread.     

Poliovirus seroprevalence before and after interruption of poliovirus transmission in Kano State,Nigeria

IntroductionIn September 2015, Nigeria was removed from the list of polio-endemic countries after more than 12 months had passed since the detection of last wild poliovirus case in the country on 24 July 2014. We are presenting here a report of two polio seroprevalence surveys conducted in September 2013 and October 2014, respectively, in the Kano state of northern Nigeria.MethodsHealth facility based seroprevalence surveys were undertaken at Murtala Mohammad Specialist Hospital, Kano. Parents or guardians of children aged 6–9 months, 36–47 months, 5–9 years and 10–14 years in 2013 and 6–9 months and 19–22 months (corresponding to 6–9 months range at the time of 2013 survey) in 2014 presenting to the outpatient department, were approached for participation, screened for eligibility and asked to provide informed consent. A questionnaire was administered and a blood sample collected for polio neutralization assay.ResultsAmong subjects aged 6–9 months in the 2013 survey, seroprevalence was 58% (95% confidence interval [CI] 51–66%) to poliovirus type 1, 42% (95% CI 34–50%) to poliovirus type 2, and 52% (95% CI 44–60%) to poliovirus type 3. Among children 36–47 months and older, seroprevalence was 85% or higher for all three serotypes. In 2014, seroprevalence in 6–9 month infants was 72% (95% CI 65–79%) for type 1, 59% (95% CI 52–66%) for type 2, and 65% (95% CI 57–72%) for type 3 and in 19–22 months, 80% (95% CI 74–85%), 57% (49–63%) and 78% (71–83%) respectively. Seroprevalence was positively associated with history of increasing oral poliovirus vaccine doses.ConclusionsThere was significant improvement in seroprevalence in 2014 over the 2013 levels indicating a positive impact of recent programmatic interventions. However the continued low seroprevalence in 6–9 month age is a concern and calls for improved immunization efforts to sustain the polio-free Nigeria.     

Population immunity to polioviruses in the context of a large-scale wild poliovirus type 1 outbreak in Tajikistan, 2010

Background

A serosurvey to evaluate population immunity to polioviruses (PVs) in the context of the importation-related wild PV1 outbreak in Tajikistan in 2010 (461 confirmed cases among children and young adults) was conducted.

Methods

Serum specimens from a nationwide sample of 1–24 year-old persons selected through stratified cluster sampling (n = 2447) were tested for neutralizing antibodies to all three PV types. Samples with titers < 1:8 were considered seronegative. The serosurvey was conducted during the interval after mOPV1 supplementary immunization activities (SIAs) and before tOPV SIAs (targeting ages ≤ 15 years) implemented to control the outbreak. In the absence of pre-outbreak specimens, results for PV3 were used as a proxy for pre-outbreak PV1 immunity patterns.

Results

Overall, PV1 seroprevalence was 98.9%, PV2 seroprevalence was 98.8%, and PV3 seroprevalence was 86.9%. PV1 and PV2 seroprevalence exceeded 95% in all age groups and regions. PV3 seroprevalence was <90% in all age groups and regions, except 15–19 year-olds (91.7%) and Dushanbe (90.0%). PV3 seroprevalence was lowest among 1–4 (82.7%) and 5–9 (84.4%) year-olds, particularly among 1–4 year-olds in Kurgan-Tube (76.3%) and RRS (80.0%) regions. Birth cohorts immunized only through routine services (ages, 1–7 years) had lower PV3 seroprevalence than birth cohorts targeted by the SIAs during 1995–2002 (8–19 years): 82.5% versus 89.3%, p < 0.001.

Conclusions

Suboptimal (<90%) PV3 seroprevalence across wide age range suggests the outbreak resulted from accumulation of susceptibles due to suboptimal coverage over a long time period, particularly in the birth cohorts immunized only through routine services and in areas where the outbreak began (Kurgan-Tube and RRS). High PV1 seroprevalence indicates that mOPV1 SIAs with expanded target age (≤15 years) succeeded in closing the immunity gap and ongoing WPV1 transmission is unlikely. To accelerate outbreak control in areas which have been polio-free for long time, expanding SIA target age should be considered.     

Waning of anti-HAV immunity in Shijiazhuang prefecture,Hebei province,China: A comparison of seroprevalence between 1992 and 2011

Objective

To study the epidemiological patterns of hepatitis A, and immunity of entire population in Shijiazhuang prefecture, Hebei province, a former hyper-endemic area in north China.

Methods

Cross-sectional, seroprevalence surveys with two-stage cluster sampling were conducted among population older than 2-year between 1992 and 2011. During the 2011 serological survey, blood samples from infants <18 months without hepatitis A immunization history were also collected to determine maternal anti-HAV antibody. Serum samples were tested for anti-HAV antibody by domestic reagent or Abbott reagent. Viral hepatitis incidence rates and gross domestic product data were derived from local governmental statistics.

Results

Concomitant with the reduction of reported hepatitis A cases between 1992 and 1996 was a significant decline of HAV infections. The average prevalence decreased from 93.6% to 41.9%, and the average age at new infection was postponed from infancy to adolescence. This was attributed to improved socio-economic conditions. With intensive vaccination, a return of new seroconversion rate and seroprevalence was observed. A well fitted exponential regression equation (R² = 0.96, p < 0.0001) modeled that the maternal antibody would wane to <20 mIU/mL at 13 months.

Conclusion

Benefiting from the booming economy, rapid improvement in sanitation, safe water supply, and implementation of hepatitis A vaccines, the epidemiological pattern of hepatitis A moved from high to intermediate endemicity in Shijiazhuang. Policy makers should be aware of the waning of immunity in entire population, and adapt immunization strategy timely, to ensure a lifelong protection against hepatitis A virus.     

Survey of poliovirus antibodies in Kano,Northern Nigeria

Introduction

In 1988, the World Health Assembly resolved to eradicate poliomyelitis. Since then, much progress towards this goal has been made, but three countries including Nigeria remain polio-endemic as of end 2012. To assess the immunity level against poliomyelitis in young children in Northern Nigeria, we conducted a seroprevalence survey in the Kano Metropolitan Area (KMA) in May 2011.

Methods

Parents or guardians of infants aged 6–9 months or children aged 36–47 months presenting to the outpatient department of Murtala Mohammad Specialist Hospital were approached for participation, screened for eligibility and were asked to provide informed consent. After that, a questionnaire was administered and blood was collected for neutralization assay.

Results

A total of 327 subjects were enrolled. Of these, 313 (96%) met the study requirements and were analyzed (161 [51%] aged 6–9 months and 152 [49%] aged 36–47 months). Among subjects aged 6–9 months, seroprevalence was 81% (95% confidence interval [CI] 75–87%) to poliovirus type 1, 76% (95% CI 68–81%) to poliovirus type 2, and 73% (95% CI 67–80%) to poliovirus type 3. Among subjects aged 36–47 months, the seroprevalence was 91% (95% CI 86–95%) to poliovirus type 1, 87% (95% CI 82–92%) for poliovirus type 2, and 86% (95% CI 80–91%) to poliovirus type 3. Seroprevalence was associated with history of oral poliovirus vaccine (OPV) doses, maternal education and gender.

Conclusions

Seroprevalence is lower than required levels for poliovirus interruption in the KMA. Persistence of immunity gaps in the 36–47 months group is a big concern. Since higher number of vaccine doses is associated with higher seroprevalence, it implies that failure-to-vaccinate and not vaccine failure accounts for the suboptimal seroprevalence. Intensified efforts are necessary to administer polio vaccines to all target children and surpass the threshold levels for herd immunity.     

Seroprevalence of neutralizing antibodies to measles virus in a vaccinated population in Iran, 1998

Measles is an acute highly infectious viral disease. Although live attenuated vaccine is used throughout the world, outbreaks of disease still occur in many countries including Iran. In this cross-sectional study, by implementing a viral neutralization test and cell culture techniques, the seroprevalence of neutralizing anti-measles antibodies was assessed. Three hundred and fifty-four blood samples were collected and random-cluster classified from healthy subjects 6 months to 16 years old, residing in the town of Khodabandeh and its rural areas. Of the total subjects, 174 (49.2%) were girls and 180 (50.8%) were boys. From 354 subjects studied, 310 (87.6%) had neutralizing anti-measles antibody titer of 1:8 or higher and were considered to be immune and 44 (12.4%) had lower antibody titers. At the time of specimen collection, information with regards to age, sex, history of vaccination and place of residence were collected. ² statistical test demonstrated a significant association between immune status and grouped age at the time of first vaccination (p < 0.009). The proportion test indicated significant differences in rate of seropositivity in paired age groups (3–8 vs. 9–11 and 9–11 vs. 12–64 months) (p < 0.02). The use of reliable techniques for assessing success of vaccination programs and performing seroepidemiological studies in order to organize national programs of control and eradication of measles are necessary.     

Polio immunity and the impact of mass immunization campaigns in the Democratic Republic of the Congo

BackgroundIn order to prevent outbreaks from wild and vaccine-derived poliovirus, maintenance of population immunity in non-endemic countries is critical.MethodsWe estimated population seroprevalence using dried blood spots collected from 4893 children 6–59 months olds in the 2013–2014 Demographic and Health Survey in the Democratic Republic of the Congo (DRC).ResultsPopulation immunity was 81%, 90%, and 70% for poliovirus types 1, 2, and 3, respectively. Among 6–59-month-old children, 78% reported at least one dose of polio in routine immunization, while only 15% had three doses documented on vaccination cards. All children in the study had been eligible for at least two trivalent oral polio vaccine campaigns at the time of enrollment; additional immunization campaigns seroconverted 5.0%, 14%, and 5.5% of non-immune children per-campaign for types 1, 2, and 3, respectively, averaged over relevant campaigns for each serotype.ConclusionsOverall polio immunity was high at the time of the study, though pockets of low immunity cannot be ruled out. The DRC still relies on supplementary immunization campaigns, and this report stresses the importance of the quality and coverage of those campaigns over their quantity, as well as the importance of routine immunization.     

Identify the susceptibility profile to measles in the general population: Serological survey of measles antibodies in Shaanxi province,China, in 2016

The reported coverage with two doses of the measles vaccine (MCV) in Shaanxi Province, China, is greater than 95%, but the measles incidence over the whole province remains high. Cross-sectional serological surveys of measles antibodies in Shaanxi Province were conducted in 2016 to assess the population’s immunity. The measles IgG levels were measured in serum samples using ELISA. The geometric means concentration (GMC) levels and seroprevalence rates with 95% CIs were calculated by region, gender, and age. A total of 3574 serum samples were collected from participants aged from 2 months to 49 years. The GMC of measles antibodies was 471.3 mIU/ml (95% CI: 445.9–498.2 mIU/ml), and the seroprevalence was only 85.9% (95% CI: 84.8–87.1%). A significant difference in the GMC (P < .05) but not the seroprevalence (P > .05) was observed among the 3 regions. The report measles incidences were high in individuals aged 0–7 months (33.2/100 000) and 8–17 months (26.8/100 000). Although both measles immunity (90.7%) and MCV coverage (89.7%) were low in children aged 8–17 months, the measles seroprevalence in adults was high at greater than 90%. These results revealed that further actions may be taken to increase vaccination coverage in children aged 8 months to 5 years over the whole province and teenagers in the south region. In particular, timely administration of the first MCV dose should be emphasized to prevent measles epidemics in children aged 8–17 months. Vaccination strategies may be varied by age and region.     

Measles and rubella immunity in the population of Bhutan, 2017

BackgroundIn 2017, measles elimination was verified in Bhutan, and the country appears to have sufficiently high vaccination coverage to achieve rubella elimination. However, a measles and rubella serosurvey was conducted to find if any hidden immunity gaps existed that could threaten Bhutan’s elimination status.MethodsA nationwide, three-stage, cluster seroprevalence survey was conducted among individuals aged 1–4, 5–17, and >20 years in 2017. Demographic information and children’s vaccination history were collected, and a blood specimen was drawn. Serum was tested for measles and rubella immunoglobulin G (IgG). Frequencies, weighted proportions, and prevalence ratios for measles and rubella seropositivity were calculated by demographic and vaccination history, taking into account the study design.ResultsOf the 1325 individuals tested, 1045 (81%, 95% CI 78%–85%) were measles IgG seropositive, and 1290 (97%, 95% CI 95%–99%) were rubella IgG seropositive. Rubella IgG seropositivity was high in all three age strata, but only 47% of those aged 5–17 years were measles IgG seropositive. Additionally, only 41% of those aged 5–17 years who had documented receipt of two doses of measles– or measles-rubella–containing vaccine were seropositive for measles IgG, but almost all these children were rubella IgG seropositive.ConclusionsAn unexpected measles immunity gap was identified among children 5–17 years of age. It is unclear why this immunity gap exists; however, it could have led to a large outbreak and threatened sustaining of measles elimination in Bhutan. Based on this finding, a mass vaccination campaign was conducted to close the immunity gap.     

Measles and rubella IgG seroprevalence in persons 6 month-35 years of age,Mongolia, 2016

BackgroundIn 2015–2016, Mongolia experienced an unexpected large measles outbreak affecting mostly young children and adults. After two nationwide vaccination campaigns, measles transmission declined. To determine if there were any remaining immunity gaps to measles or rubella in the population, a nationally representative serosurvey for measles and rubella antibodies was conducted after the outbreak was over.MethodsA nationwide, cross-sectional, stratified, three-stage cluster serosurvey was conducted in November-December 2016. A priori, four regional strata (Ulaanbaatar, Western, Central, and Gobi-Eastern) and five age strata (6 months-23 months, 2–7 years, 8–17 years, 18–30 years, and 31–35 years) were created. Households were visited, members interviewed, and blood specimens were collected from age-appropriate members. Blood specimens were tested for measles immunoglobulin G (IgG) and rubella IgG (Enzygnost® Anti-measles Virus/IgG and Anti-rubella Virus/IgG, Siemens, Healthcare Diagnostics Products, GmbH Marburg, Germany). Factors associated with seropositivity were evaluated.ResultsAmong 4598 persons aged 6 months to 35 years participating in the serosurvey, 94% were measles IgG positive and 95% were rubella IgG positive. Measles IgG seropositivity was associated with increasing age and higher education. Rubella IgG seropositivity was associated with increasing age, higher education, smaller household size, receipt of MMR in routine immunization, residence outside the Western Region, non-Muslim religious affiliation, and non-Kazakh ethnicity. Muslim Kazakhs living in Western Region had the lowest rubella seroprevalence of all survey participants.ConclusionsNationally, high immunity to both measles and rubella has been achieved among persons 1–35 years of age, which should be sufficient to eliminate both measles and rubella if future birth cohorts have ≥ 95% two dose vaccination coverage. Catch-up vaccination is needed to close immunity gaps found among some subpopulations, particularly Muslim Kazakhs living in Western Region.     

Using Open-Ended Data to Enrich Survey Results on the Meanings of Self-Rated Health: A Study Among Women in Underprivileged Communities in Beirut,Lebanon

This study extends the debate on self-rated health by using different sources of data in the same study to explore the meanings of self-rated health among women who live in socio-economically disadvantaged communities in Beirut, Lebanon. Using data from the Urban Health Study, a cross-sectional household survey of 1,869 women between 15 and 59 years of age, multiple logistic regression models were developed to assess factors associated with self-rated health. Also, open-ended data was used to analyze women's explanations of their self-rated health ratings. Self-rated health was found to be a complex concept, associated not only with physical health but also with a combination of social, psychological, and behavioral factors. This open-ended analysis revealed new meanings of self-rated health that are often not included in self-rated health epidemiologic research, such as women's experiences with pain and fatigue, as well as exposure to financial stressors and the legacy of wars. We argue that triangulating survey and open-ended data provides a better understanding of the context-specific social and cultural meanings of self-rated health.     

A population profile of measles susceptibility in Tianjin,China

BackgroundMeasles is a highly infectious illness requiring herd immunity of 95% to interrupt transmission. Measles is targeted for elimination in China, which has not reached elimination goals despite high vaccination coverage. We developed a population profile of measles immunity among residents aged 0–49 years in Tianjin, China.MethodsParticipants were either from community population registers or community immunization records. Measles IgG antibody status was assessed using dried blood spots. We examined the association between measles IgG antibody status and independent variables including urbanicity, sex, vaccination, measles history, and age.Results2818 people were enrolled. The proportion measles IgG negative increased from 50.7% for infants aged 1 month to 98.3% for those aged 7 months. After 8 months, the age of vaccination eligibility, the proportion of infants and children measles IgG negative decreased. Overall, 7.8% of participants 9 months of age or older lacked measles immunity including over 10% of those 20–39 years. Age and vaccination status were significantly associated with measles IgG status in the multivariable model. The odds of positive IgG status were 0.337 times as high for unvaccinated compared to vaccinated (95% CI: 0.217, 0.524).ConclusionsThe proportion of persons in Tianjin, China immune to measles was lower than herd immunity threshold with less than 90% of people aged 20–39 years demonstrating protection. Immunization programs in Tianjin have been successful in vaccinating younger age groups although high immunization coverage in infants and children alone would not provide protective herd immunity, given the large proportion of non-immune adults.     

Serum antibodies to polioviruses in a Tuscan population,Italy

In order to study the serological status of a population against poliomyelitis, neutralizing antibody for the three types of polioviruses were examined in 742 serum specimens from individuals aged from 1 to 70 years and over were collected during 1985. Sixty-two percent of the sera had antibodies (titre 1:8) to all three polioviruses, while 5% had no poliovirus antibody at all. However the rates of seropositivity did vary with age: the 10–19 age group had the lowest frequency of antibody (38%) to the three viruses and the difference between the percentage of this group and the previous (1–10 years) and following ones (20–70 years and over) was highly significant. The results of this seroprevalence survey indicate a gap in immunity to poliomyelitis in the population examined.     

Effect of maternal immunisation with multivalent vaccines containing inactivated poliovirus vaccine (IPV) on infant IPV immune response: A phase 4, multi-centre randomised trial

Multivalent diphtheria, tetanus, acellular pertussis and inactivated poliovirus vaccine (DTaP/IPV) has been offered to pregnant women in the United Kingdom since 2012. To assess the impact of maternal DTaP/IPV immunisation on the infant immune response to IPV, we measured poliovirus-specific neutralising antibodies at 2, 5 and 13 months of age in a randomised, phase 4 study of Repevax or Boostrix/IPV in pregnancy and in a non-randomised group born to women not given DTaP/IPV in pregnancy. Infants whose mothers received DTaP/IPV were less likely to seroconvert after three IPV doses than those whose mothers did not receive DTaP/IPV. At 13 months of age, 63/110 (57.2 %), 46/108 (42.6 %) and 40/108 (37.0 %) were seropositive to types 1 to 3, compared with 20/22 (90.9 %), 20/22 (90.9 %) and 14/20 (70.0 %) (p-values 0.003, <0.001 and 0.012). UK infants whose mothers are given DTaP/IPV in pregnancy may be insufficiently protected against poliomyelitis until their pre-school booster.     

开封市2005～2011年急性弛缓性麻痹病例监测结果分析

目的 评价开封市2005～2011年急性弛缓性麻痹(AFP)监测系统的运转情况,指导维持无脊髓灰质炎(脊灰)状态.方法 用EpiInfo和Excel软件分析开封市2005～2011年AFP监测病例.结果 开封市2005～2011年共报告15岁以下儿童本地AFP病例222例,年平均报告发病率2.86/10万,无脊灰病毒野毒株检出和脊髓灰质炎病例报告;系统监测的敏感性、及时性和完整性指标均达到世界卫生组织和卫生部要求.结论 要维持无脊灰状态,应继续保持高质量的AFP病例监测和高水平的口服脊髓灰质炎疫苗计划免疫率.     

Persistence of immunity to poliomyelitis among a southern population that received four doses of OPV 5 to over 15 years before

The immune status against polioviruses was investigated in a population of 545 students aged 11–20 years residing in the Neapolitan area, who had completed the vaccination cycle with four doses of OPV 5 to over 15 years before. Assuming as unprotected those individuals without detectable neutralizing antibodies at the dilution 1:2, nobody resulted without protection against all types of poliovirus; 0.7% lacked antibodies only against type 1, 0.6% only against type 3 and none against type 2. A very slight decreasing trend was observed for GMT values in function of the distance from the last dose of OPV for polio 1 and 2, but not for polio 3. As expected, GMT values for polio 2 resulted higher than those for polio 1 and both were higher than those for polio 3, when calculated by age groups as well as by distance groups. The last four Italian cases of autoctonous paralytic poliomyelitis, occurred in the period 1981/83, regarded unvaccinated children aged 6 months – 2 years, residing in the same geographical area to which the study population belong. In the same area a delay of immunization practices was also ascertained in the recent past. Results of this study confirm that a priority for public health services is to devote their human and economic resources to reduce the vaccination delay more than administrate a further fifth dose of OPV at the age of twelve.     

Preventive Healthcare of Infants in a Region of Lebanon: Parental Beliefs,Attitudes and Behaviors

Objectives: This study aimed to investigate healthcare seeking behaviors of mothers for themselves and their infants in the Bekaa Valley, Lebanon, to identify attitudes and beliefs towards the preventive healthcare of infants and to assess whether a healthcare-based intervention program would be accepted by the population. Methods: Ninety-two interviews were conducted with women who had delivered a live birth in two hospitals in the Bekaa. The hospitals selected attracted women from different socioeconomic classes. Results: Differences were found in adequacy of healthcare utilization based on household size, number of children and prenatal care utilization. There was a higher perception of barriers to healthcare by parents who did not seek adequate preventive care for their infants. Mothers of infants who had inadequate care had a lower perception of severity of illness and of physicians ability to prevent illness. The population believes strongly that medical professionals are reliable sources of health information and guidance. Infants mothers and grandmothers are important sources of healthcare-related information. Conclusions: Rates of preventive infant healthcare in the Bekaa need improvement. Any intervention must target mothers and grandmothers, as they appear to influence the medical care of infants. Other targets include parents of larger families. Dissemination of information regarding the seriousness of illness and the ability to prevent illness is required. The medical profession may influence health choices made by this population. However, further investigation of healthcare barriers, especially economic and geographic barriers, is needed. In preparing to improve healthcare utilization for infants in the Bekaa, local, regional and international organizations should refer to the populations beliefs, attitudes and behaviors described in this study, as these findings may aid in planning interventions that are likely to positively impact mothers and infants.     

Changes in seroprevalence to hepatitis A in Victoria, Australia: A comparison of three time points

Serological data provide an important measure of past exposure and immunity to hepatitis A virus (HAV) infection in a population. National serosurveys from developed countries have typically indicated a decline in HAV seroprevalence over time as sanitation levels improve. We examined trends in the seroepidemiology of HAV antibodies in Victoria, Australia, drawing on cross-sectional samples taken at three time points over a 20-year period. Stored sera from 1988 (n=753), 1998 (n=1091), and 2008 (n=791) from persons aged 1-69 years were obtained from the state of Victoria, Australia. The within-year population adjusted results show a significant trend of increasing population HAV seroprevalence over time from 34.3% (95% CI 31.7-36.9) in 1988, to 40.0% (95% CI 37.1-42.8) in 1998 and 55.1% (95% CI 52.1-58.1) in 2008, P<0.0001. A particularly noticeable rise in population seroprevalence was observed between 1998 and 2008 for those aged 5-39 years. The increase in HAV seropositivity over time is in contrast to the declining rates of disease notification in Australia. Based on comparisons with other Australian data, it appears the increase in population seroprevalence over the last two decades is unlikely to be due to endemic transmission of infection. Instead, other factors, including increases in travel to HAV endemic regions, migration to Australia from HAV endemic regions and vaccine uptake are more likely causes. Ongoing monitoring of serological HAV profiles in the population is required to determine future policy direction to prevent increased burden.