Age-adjusted Seroprevalence Research Articles

Cross-Sectional Study of Q Fever Seroprevalence among Blood Donors, Israel, 2021.

We evaluated Q fever prevalence in blood donors and assessed the epidemiologic features of the disease in Israel in 2021. We tested serum samples for Coxeilla burnetii phase I and II IgG using immunofluorescent assay, defining a result of >200 as seropositive. We compared geographic and demographic data. We included 1,473 participants; 188 (12.7%) were seropositive. The calculated sex- and age-adjusted national seroprevalence was 13.9% (95% CI 12.2%-15.7%). Male sex and age were independently associated with seropositivity (odds ratio [OR] 1.6, 95% CI 1.1-2.2; p = 0.005 for male sex; OR 1.2, 95% CI 1.01-1.03; p<0.001 for age). Residence in the coastal plain was independently associated with seropositivity for Q fever (OR 1.6, 95% CI 1.2-2.3; p<0.001); residence in rural and farming regions was not. Q fever is highly prevalent in Israel. The unexpected spatial distribution in the nonrural coastal plain suggests an unrecognized mode of transmission.

High prevalence of trachomatous inflammation-follicular with no trachomatous trichiasis: can alternative indicators explain the epidemiology of trachoma in Côte d'Ivoire?

Baseline trachoma surveys in Côte d'Ivoire (2019) identified seven evaluation units (EUs) with a trachomatous inflammation-follicular (TF) prevalence ≥10%, but a trachomatous trichiasis (TT) prevalence in individuals ≥15y of age below the elimination threshold (0.2%). Two of these EUs, Bondoukou 1 and Bangolo 2, were selected for a follow-up survey to understand the epidemiology of trachoma using additional indicators of Chlamydia trachomatis infection (DNA from conjunctival swabs) and exposure (anti-Pgp3 and Ct694 antibodies from dried blood spots [DBSs]). A two-stage cluster sampling methodology was used to select villages and households. All individuals 1-9y of age from each selected household were recruited, graded for trachoma and had a conjunctival swab and DBS collected. Conjunctival swabs and DBSs were tested using Cepheid GeneXpert and a multiplex bead assay, respectively. The age-adjusted TF and infection prevalence in 1- to 9-year-olds was <1% and <0.3% in both EUs. Age-adjusted seroprevalence was 5.3% (95% confidence interval [CI] 1.5 to 15.6) in Bondoukou 1 and 8.2% (95% CI 4.3 to 13.7) in Bangolo 2. The seroconversion rate for Pgp3 was low, at 1.23 seroconversions/100 children/year (95% CI 0.78 to 1.75) in Bondoukou 1 and 1.91 (95% CI 1.58 to 2.24) in Bangolo 2. Similar results were seen for CT694. These infection, antibody and clinical data provide strong evidence that trachoma is not a public health problem in either EU.

SARS-CoV-2 specific IgG antibodies among participants presenting to a voluntary testing facility in Srinagar, Kashmir.

ABSTRACTBackground:The tide of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) pandemic has scoured the global community with India, from 30 January 2020 to 30 September 2021, reporting 33,739,980 confirmed cases and over 448,090 deaths from coronavirus disease (COVID-19). Serologic testing for SARS-CoV-2 infection among the general public will provide essential information regarding the risk of infection. So, the present study was conducted to provide relevant information on the proportion of people who hadexperienced either a recent or past infection.Methodology:A cross-sectional study was conducted among adults >18 years in the Department of Community Medicine, Government medical college, Srinagar. Blood samples of the participants were tested for the presence of SARS-CoV-2-specific IgG antibodies using a chemiluminescent microparticle immunoassay-based serologic test.Results:A total of 2,107 participants took part in the study. The overall unadjusted seroprevalence of IgG antibodies against SARS-CoV-2 in our study was 49%. The age-adjusted seroprevalence was 52%.Conclusion:The findings of the study suggested that not only a large proportion (49%) of the participants had been infected with COVID-19 infection but many were also susceptible to infection. Therefore, infection control measures still need to be followed properly.

Toxoplasma gondii Infection in the United States, 2011-2014.

Toxoplasma gondii can cause severe neurologic and ocular disease when transmitted congenitally and in immunosuppressed persons. Sera collected in the National Health and Nutrition Examination Survey 2011 through 2014 in 13,507 persons ≥ 6 years old were tested for T. gondii immunoglobulin (Ig) G and IgM antibodies, and in those both IgG and IgM antibody positive, for IgG avidity. Overall, 11.14% (95% confidence limits [CL] 9.88%, 12.51%) were seropositive for T. gondii IgG antibody (age-adjusted seroprevalence 10.42% [95% CL 9.19%, 11.76%]); in women aged 15-44 years, the age-adjusted T. gondii IgG seroprevalence was 7.50% (95% CL 6.00%, 9.25%). In multivariable analysis, risk for IgG seropositivity increased with age and was higher in males; persons living below the poverty level; persons with ≤ a high school education compared with those with > a high school education; and non-Hispanic black, Mexican American, and foreign born non-Hispanic white persons compared with U.S.-born non-Hispanic white persons. Overall, 1.16% (95% CL 0.94%, 1.42%) were T. gondii IgM antibody positive and 0.71%, (95% CL 0.54%, 0.92%) were both IgM and IgG antibody positive. In multivariable analysis, the significant risk factors for being both IgM and IgG positive were older age, crowding, and non-U.S. birth origin compared with U.S.-born persons. Among those positive for both IgM and IgG antibody, almost all had high avidity (all women aged 15-44 years had high avidity). Toxoplasma gondii antibody prevalence remains relatively low in the United States, although it is higher in non-U.S.-born persons, males, and some minority and socioeconomically disadvantaged groups.

Seroprevalence of Hepatitis A Twelve Years After the Implementation of Toddlers' Vaccination: A Population-Based Study in Israel.

In 1999, Israel became the first country to introduce an inactivated hepatitis A vaccine into its national childhood vaccination program. The objective of the present study was to evaluate the seroprevalence of hepatitis A virus antibodies in the Israeli population before and after the introduction of the program. A cross-sectional serosurvey using the National Serum Bank was conducted on 1883 and 2027 serum samples collected before and after introduction of the vaccine, respectively. Serologic tests for the presence of hepatitis A IgG antibodies were performed using an automated enzyme-linked fluorescent assay. The age-adjusted seroprevalence rates of hepatitis A virus antibodies before implementation of hepatitis A vaccination program were 47.1% [95% confidence interval (CI): 44.7%-49.5%] among Jews and 82.8% (95% CI: 79.6%-85.9%) among Arabs, increasing 12 years after to 67.4% (95% CI: 64.7%-70.0%) and 88.2% (95% CI: 86.1%-90.2%), respectively. The seropositivity rate among Jews and Arabs increased significantly among the cohorts included in the program. However, among Jews, a significant increase in seropositivity was also detected among age groups not included in the vaccination program. The decrease in the incidence of hepatitis A in Israel is a consequence of high vaccine uptake, persistent seropositivity rates after vaccination and the considerable number of people vaccinated beyond the program.

Current and cumulative malaria infections in a setting embarking on elimination: Amhara, Ethiopia

BackgroundSince 2005, Ethiopia has aggressively scaled up malaria prevention and case management. As a result, the number of malaria cases and deaths has significantly declined. In order to track progress towards the elimination of malaria in Amhara Region, coverage of malaria control tools and current malaria transmission need to be documented.MethodsA cross-sectional household survey oversampling children under 5 years of age was conducted during the dry season in 2013. A bivalent rapid diagnostic test (RDT) detecting both Plasmodium falciparum and Plasmodium vivax and serology assays using merozoite antigens from both these species were used to assess the prevalence of malaria infections and exposure to malaria parasites in 16 woredas (districts) in Amhara Region.Results7878 participants were included, with a mean age of 16.8 years (range 0.5–102.8 years) and 42.0% being children under 5 years of age. The age-adjusted RDT-positivity for P. falciparum and P. vivax infection was 1.5 and 0.4%, respectively, of which 0.05% presented as co-infections. Overall age-adjusted seroprevalence was 30.0% for P. falciparum, 21.8% for P. vivax, and seroprevalence for any malaria species was 39.4%. The prevalence of RDT-positive infections varied by woreda, ranging from 0.0 to 8.3% and by altitude with rates of 3.2, 0.7, and 0.4% at under 2000, 2000–2500, and >2500 m, respectively. Serological analysis showed heterogeneity in transmission intensity by area and altitude and evidence for a change in the force of infection in the mid-2000s.ConclusionsCurrent and historic malaria transmission across Amhara Region show substantial variation by age and altitude with some settings showing very low or near-zero transmission. Plasmodium vivax infections appear to be lower but relatively more stable across geography and altitude, while P. falciparum is the dominant infection in the higher transmission, low-altitude areas. Age-dependent seroprevalence analyses indicates a drop in transmission occurred in the mid-2000s, coinciding with malaria control scale-up efforts. As malaria parasitaemia rates get very low with elimination efforts, serological evaluation may help track progress to elimination.

High Hepatitis E Seroprevalence Among Displaced Persons in South Sudan.

Large protracted outbreaks of hepatitis E virus (HEV) have been documented in displaced populations in Africa over the past decade though data are limited outside these exceptional settings. Serological studies can provide insights useful for improving surveillance and disease control. We conducted an age-stratified serological survey using samples previously collected for another research study from 206 residents of an internally displaced person camp in Juba, South Sudan. We tested serum for anti-HEV antibodies (IgM and IgG) and estimated the prevalence of recent and historical exposure to the virus. Using data on individuals' serostatus, camp arrival date, and state of origin, we used catalytic transmission models to estimate the relative risk of HEV infection in the camp compared with that in the participants' home states. The age-adjusted seroprevalence of anti-HEV IgG was 71% (95% confidence interval = 63–78), and 4% had evidence of recent exposure (IgM). We estimated HEV exposure rates to be more than 2-fold (hazard ratio = 2.3, 95% credible interval = 0.3–5.8) higher in the camp than in the participants' home states, although this difference was not statistically significant. HEV transmission may be higher than previously appreciated, even in the absence of reported cases. Improved surveillance in similar settings is needed to understand the burden of disease and minimize epidemic impact through early detection and response.

Herpes virus seroepidemiology in the adult Swedish population

BackgroundHerpes viruses establish a life-long latency and can cause symptoms during both first-time infection and later reactivation. The aim of the present study was to describe the seroepidemiology of Herpes simplex type 1 (HSV1), Herpes simplex type 2 (HSV2), Cytomegalovirus (CMV), Varicella Zoster virus (VZV) and Human herpes virus type 6 (HHV6) in an adult Swedish population (35–95 years of age).MethodsPresence of antibodies against the respective viruses in serum from individuals in the Betula study was determined with an enzyme-linked immunosorbent assay (ELISA). Singular samples from 535 persons (53.9% women, mean age at inclusion 62.7 ± 14.4 years) collected 2003-2005 were analyzed for the five HHVs mentioned above. In addition, samples including follow-up samples collected 1988–2010 from 3,444 persons were analyzed for HSV.ResultsPrevalence of HSV1 was 79.4%, HSV2 12.9%, CMV 83.2%, VZV 97.9%, and HHV6 97.5%. Herpes virus infections were more common among women (p = 0.010) and a lower age-adjusted HSV seroprevalence was found in later birth cohorts (p < 0.001). The yearly incidence of HSV infection was estimated at 14.0/1000.ConclusionWomen are more often seropositive for HHV, especially HSV2. Age-adjusted seroprevalence for HSV was lower in later birth cohorts indicating a decreasing childhood and adolescent risk of infection.

Diagnosis, Treatment, and Prevention of Congenital Toxoplasmosis in the United States.

* Abbreviations: AC/HS — : differential agglutination (test) AF — : amniotic fluid CI — : confidence interval CNS — : central nervous system CSF — : cerebrospinal fluid CT — : congenital toxoplasmosis ELISA — : enzyme-linked immunosorbent assay EMSCOT — : European Multicenter Study of Congenital Toxoplasmosis EUROTOXO — : European Toxoprevention Study FDA — : US Food and Drug Administration GRADE — : Grading of Recommendations Assessment, Development, and Evaluation HR — : hazard ratio Ig — : immunoglobulin ISAGA — : immunosorbent agglutination assay MTCT — : mother-to-child transmission NCCCT — : National Collaborative Chicago-Based Congenital Toxoplasmosis Study NPV — : negative predictive value OR — : odds ratio PAMF-TSL — : Palo Alto Medical Foundation Toxoplasma Serology Laboratory PCR — : polymerase chain reaction PPV — : positive predictive value P/S — : pyrimethamine/sulfadiazine RCT — : randomized controlled trial SNHL — : sensorineural hearing loss SNSD — : serious neurologic sequelae or death SYROCOT — : Systematic Review on Congenital Toxoplasmosis Congenital toxoplasmosis (CT) is a parasitic disease that can cause significant fetal and neonatal harm. Coordinated efforts by pregnant women, researchers, physicians, and health policy makers regarding potential primary and secondary preventive measures for CT and their implementation may lead to a lower incidence of CT as well as lower morbidity and mortality rates associated with CT. In the United States, the age-adjusted seroprevalence of Toxoplasma gondii among women of childbearing age (15–44 years) has declined over time (15%, 11%, and 9% in 1988–1994, 1999–2004, and 2009–2010, respectively; among US-born women only, the seroprevalence rates during these time periods were 13%, 8%, and 6%, respectively). Thus, approximately 91% of women of childbearing age in the United States are susceptible to Toxoplasma infection. Should these women become infected during pregnancy and remain undiagnosed and untreated, they could deliver an infant with CT. However, the incidence of acute primary infection is likely very low in the current era and is probably much lower than the 1.1 in 1000 pregnant women originally reported in 1960s. There are 3 ways CT can occur. First, CT can develop through transmission of T gondii to the fetus from a previously seronegative, immunocompetent mother who acquired acute primary infection during pregnancy or within 3 months before …

Prevalence and incidence of toxoplasmosis: a retrospective analysis of mother-child examinations, Styria, Austria, 1995 to 2012.

In Austria, mandatory screening for the prevention of congenital toxoplasmosis stipulates a serological test for antibodies against Toxoplasma gondii as early as possible in pregnancy. In the case of a seronegative result, subsequent tests at intervals of 8 weeks are requested. We analysed serological data from Styria, an Austrian federal state, to determine the seroprevalence and incidence of Toxoplasma infections. The study included 353,599 tests from 103,316 women during 158,571 pregnancies from 1995 to 2012. The age-adjusted seroprevalence decreased from 43.3% in 1995 to 31.5% in 2012, with a yearly decline of 0.84% (95% confidence interval (CI): 0. 79 -0.88). The intergravid incidence showed an annual decrease of 4.2%. The average yearly incidence of intragravid and intergravid seroconversions was 0.52% (95% CI 0.45–0.61) and 0.72% (95% CI 0.67–0.77), respectively. If the difference between these rates (p < 0.001) can be explained by the effect of primary prevention such as avoiding raw meat and taking hygiene precautions when encountering cats or preparing vegetables, only ca two of seven (28%) infections were avoided by hygiene measures taken by pregnant women. Primary prevention may therefore have its limits.

Influence of parity and sexual history on cytomegalovirus seroprevalence among women aged 20–49 years in the USA

ObjectiveTo assess the influence of parity, as a proxy for exposure to children, and sexual history on cytomegalovirus (CMV) seroprevalence. MethodsData were retrospectively analyzed from women aged 20–49 years who were tested for CMV immunoglobulin G antibodies in the 1999–2004 National Health and Nutrition Examination Survey, a nationally representative survey of the US population. Logistic regression was used to determine independent variables associated with CMV seroprevalence. ResultsAmong 3710 women, the age-adjusted CMV seroprevalence was 61.3% (95% CI 58.9%–63.6%). In age-adjusted univariate analysis, women who had given birth at least once had higher overall CMV seroprevalence (66.0%, 95% CI 63.1%–68.9%) than did those who had not given birth (49.0%, 95% CI 44.4%–53.7%; P<0.001). In multivariate logistic analysis, higher CMV seroprevalence was independently associated with number of live births (each additional birth: adjusted odds ratio [aOR] 1.2, 95% CI 1.1–1.3), age at first sexual intercourse (<18 vs ≥18years: aOR 1.3, 95% CI 1.1–1.6), lifetime sexual partners (≥10 vs <10: aOR 1.4, 95% CI 1.1–1.9), and herpes type 2 seropositivity (aOR 1.9, 95% CI 1.5–2.6) after controlling for age, race/Hispanic origin, place of birth, poverty index, and education. ConclusionAmong US women of reproductive age, parity and sexual exposures were independently associated with increased CMV seroprevalence.

Cytomegalovirus Seroprevalence Among Children and Adolescents in Germany: Data From the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), 2003-2006.

Background. Congenital cytomegalovirus (CMV) infection can cause severe birth defects. The majority of children with congenital CMV are born to CMV-seropositive women; however, transmission from mother to fetus and resulting defects are more likely to occur when mothers experience seroconversion during pregnancy. The objective of this study was to provide a population-based estimate of CMV seropositivity and to identify factors that correlate with the detection of CMV-immunoglobulin (Ig)G antibodies. Methods. Cytomegalovirus-specific IgG antibodies were determined by enzyme-linked immunosorbent assay in 13 876 serum samples from children and adolescents (aged 1-17 years). Cytomegalovirus seroprevalence was correlated with children's age, gender, migration background, country of origin, place of birth, socioeconomic status, breast feeding, daycare attendance, order and number of siblings, and residence in East versus West Germany. Results. Age-adjusted seroprevalence was 27.4% (95% confidence interval, 25.8-29.0). Cytomegalovirus seroprevalence increased with age (21.5% at ages 1-2; 32.0% at ages 14-17). Cytomegalovirus seropositivity was significantly associated with migration background, country of origin and place of birth, and (among migrants only) with low socioeconomic status. Risk factors for CMV acquisition included the birth order of siblings, breastfeeding, early daycare attendance, and living in East Germany. Conclusions. In Germany, CMV seroprevalence increases with age, irrespective of gender. These data highlight risk factors associated with seroprevalence and help to identify a target age for the application of a CMV vaccine.

Hepatitis C virus seroprevalence in the general female population from 8 countries

BackgroundHepatitis C virus (HCV) infection is a significant global health issue because it is widespread and persistent and can cause serious liver diseases. ObjectivesThe aim of this study is to estimate HCV prevalence in women from the general population in different geographical areas worldwide and to assess the potential role of sexual behaviour in the virus transmission. Study designEach participating centre recruited a random sample of women from the general population aged from less than 20 to more than 75 years. The study included 8130 women from 8 countries with information on sociodemographic factors, reproductive and sexual behaviour, smoking habit and HPV DNA through individual interviews. A blood sample was also collected to perform serological tests. We estimated the prevalence ratios associated to HCV to evaluate the effect of sexual behaviour in viral transmission. ResultsWomen were reactive to a minimum of two HCV antigens, including at least one non structural protein were considered as positive (33% of the samples were classified as positive, 40% as negative, and 27% as indeterminate (N=402), that were considered as not positive). The age-adjusted HCV seroprevalence varied significantly by regions (0.3% in Argentina to 21.1% in Nigeria). We found no association between HCV prevalence and age, educational level, smoking habit and any of the available variables for sexual behaviour and reproductive history. ConclusionsThis large study showed heterogeneous distribution of HCV seroprevalence in female and provides evidence of the null impact of sexual behaviour in HCV transmission.

Drinking water source and human Toxoplasma gondii infection in the United States: a cross-sectional analysis of NHANES data

BackgroundToxoplasma gondii imparts a considerable burden to public health. Human toxoplasmosis can be life-threatening in immunocompromised individuals, has been associated with psychiatric disorders, and can cause severe congenital pathologies, spontaneous abortion, or stillbirth. Environmental modes of transmission contributing to the incidence of human toxoplasmosis are poorly understood. We sought to examine National Health and Nutrition Examination Survey (NHANES) data for risk factors associated with T. gondii seroprevalence.MethodsT. gondii serology results reported for Continuous NHANES survey years 1999–2004 and 2009–10 were examined. To explore associations with toxoplasmosis seropositivity, covariates of interest were selected a priori, including source and home treatment of tap water. Associations between potential risk factors and evidence of IgG antibodies against T. gondii were assessed using multivariable logistic regression.ResultsAmong 23,030 participants with available T. gondii serology across 8 years of continuous NHANES survey data (1999–2004; 2009–2010), persons born outside the United States were significantly more likely to be seropositive, and seropositivity was inversely associated with years spent in the United States. Among US-born participants, participants with homes on well water (both those who used at-home water treatment devices and those who did not), as well as participants with public/private company-provided tap water who did not use at-home water treatment devices, were significantly more likely to be seropositive compared to participants who used home treatment devices on tap water provided by a private or public water company. A comparative subpopulation analysis revealed age-adjusted seroprevalence among US-born persons 12-49 yrs old significantly declined to 6.6% (95% CI, 5.2-8.0) (P <0.0001) in 2009–10, compared to previously published reports for NHANES data from 1988–1994 (14.1%) and 1999–2004 (9.0%).ConclusionsData suggests that T. gondii infections continue to decline in the United States, but the overall infection rate remains substantial at nearly 7%. Despite the limitations in the Continuous NHANES cross-sectional survey, the association between well water use and T. gondii infection warrants further research.

Epidemiology and seroepidemiology of human enterovirus 71 among Thai populations

BackgroundHuman enterovirus 71 (EV71) is an important pathogen caused large outbreaks in Asian-Pacific region with severe neurological complications and may lead to death in young children. Understanding of the etiological spectrum and epidemic changes of enterovirus and population’s immunity against EV71 are crucial for the implementation of future therapeutic and prophylactic intervention.ResultsA total of 1,182 patients who presented with the symptoms of hand foot and mouth disease (67.3%) or herpangina (HA) (16.7%) and admitted to the hospitals during 2008-2013 were tested for enterovirus using pan-enterovirus PCR targeting 5′-untranslated region and specific PCR for viral capsid protein 1 gene. Overall, 59.7% were pan-enterovirus positive comprising 9.1% EV71 and 31.2% coxsackievirus species A (CV-A) including 70.5% CV-A6, 27.6% CV-A16, 1.1% CV-A10, and 0.8% CV-A5. HFMD and HA occurred endemically during 2008-2011. The number of cases increased dramatically in June 2012 with the percentage of the recently emerged CV-A6 significantly rose to 28.4%. Co-circulation between different EV71 genotypes was observed during the outbreak. Total of 161 sera obtained from healthy individuals were tested for neutralizing antibodies (NAb) against EV71 subgenotype B5 (EV71-B5) using microneutralization assay. The seropositive rate of EV71-B5 was 65.8%. The age-adjusted seroprevalence for individuals was found to be lowest in children aged >6 months to 2 years (42.5%). The seropositive rate remained relatively low in preschool children aged > 2 years to 6 years (48.3%) and thereafter increased sharply to more than 80% in individuals aged > 6 years.ConclusionsThis study describes longitudinal data reflecting changing patterns of enterovirus prevalence over 6 years and demonstrates high seroprevalences of EV71-B5 NAb among Thai individuals. The rate of EV71 seropositive increased with age but without gender-specific significant difference. We identified that relative lower EV71 seropositive rate in early 2012 may demonstrate widely presented of EV71-B5 in the population before account for a large outbreak scale epidemic occurred in 2012 with due to a relatively high susceptibility of the younger population.

Seroepidemiology ofToxoplasma gondiiinfection in the Israeli population

Toxoplasmosis seroprevalence varies considerably between countries. We studied the seroprevalence of Toxoplasma gondii IgG antibodies in a national sample of the Israeli population; 2794 sera were tested. The highest age-adjusted seroprevalence rate was in Arabs (non-Bedouins) (60.4%), significantly higher compared to the rate in Jews (19.9%) and Bedouins (27.5%) (P < 0.01). There were no significant gender differences. Seropositivity increased with age in all population groups. For Jews, seropositivity was associated with place of birth and socioeconomic status. A finding of low seroprevalence rate in Bedouins despite their poor living conditions and close contact with livestock is surprising, and might be attributed to the dry and hot climate conditions in their area of residence. In women of reproductive age the seroprevalence was 15.1% in Jews, 25.4% in Bedouins and 72.3% in Arabs (non-Bedouins). Thus, the majority of pregnant women are susceptible to primary infection with T. gondii, and the risk for congenital toxoplasmosis remains high.

Trends in the seroprevalence of hepatitis B surface antigen in the South Korean population

Trends in hepatitis B virus (HBV) infection are important in evaluating the effectiveness of the recommended routine vaccination of infants and adolescents. The prevalence of HBV infection was determined in a representative sample of the Korea National Health and Nutrition Examination Survey for 1998 (n=9771) and 2009 (n=8304). Participants aged ≥10 years were tested for the hepatitis B surface antigen (HBsAg). The overall age-adjusted HBsAg seroprevalence was 4.6% (95% confidence interval (CI) 4.2-5.0%) in 1998 and 3.2% (95% CI 2.9-3.6%) in 2009, which represents a relative decrease of 30.4% between the two survey populations (p<0.05). The prevalence of HBsAg decreased among persons 10-19 years of age (from 2.2% to 0.3%), 20-29 years of age (from 5.4% to 2.5%), 30-39 years of age (from 6.1% to 4.3%), 40-49 years of age (from 5.1% to 4.7%), and 50-59 years of age (from 5.3% to 3.7%). HBsAg seroprevalence did not decrease among persons ≥60 years of age (2.7% vs. 2.9%). These data show a decline in HBsAg seroprevalence, primarily due to the dramatic decrease in adolescents and younger adults.

An age-adjusted seroprevalence study of Toxoplasma antibody in a Malaysian ophthalmology unit

Toxoplasma gondii is a public health risk in developing countries, especially those located in the tropics. Widespread infection may inflict a substantial burden on state resources, as patients can develop severe neurological defects and ocular diseases that result in lifelong loss of economic independence. We tested sera for IgG antibody from 493 eye patients in Malaysia. Overall age-adjusted seroprevalence was estimated to be 25% (95% CI: [21%, 29%]). We found approximately equal age-adjusted seroprevalence in Chinese (31%; 95% CI: [25%, 38%]) and Malays (29%; 95% CI: [21%, 36%]), followed by Indians (19%; 95% CI: [13%, 25%]). A logistic regression of the odds for T. gondii seroprevalence against age, gender, ethnicity and the occurrence of six types of ocular diseases showed that only age and ethnicity were significant predictors. The odds for T. gondii seroprevalence were 2.7 (95% CI for OR: [1.9, 4.0]) times higher for a patient twice as old as the other, with ethnicity held constant. In Malays, we estimated the odds for T. gondii seroprevalence to be 2.9 (95% CI for OR: [1.8, 4.5]) times higher compared to non-Malays, with age held constant. Previous studies of T. gondii seroprevalence in Malaysia did not explicitly adjust for age, rendering comparisons difficult. Our study highlights the need to adopt a more rigorous epidemiological approach in monitoring T. gondii seroprevalence in Malaysia.

Seroprevalence of Hepatitis A Virus Antibodies in the U.S.: Results from the National Health and Nutrition Examination Survey

We described seroprevalence of antibody to hepatitis A virus (anti-HAV) in the United States during 1999-2006 and compared it with seroprevalence before the availability of vaccine. We analyzed data from the 1988-1994 and 1999-2006 National Health and Nutrition Examination Survey (NHANES) to obtain estimates of anti-HAV seroprevalence for the U.S. household population. We grouped region of residence based on the 1999 Advisory Committee on Immunization Practices recommendations into 17 states with any recommendation (vaccinating) and 33 states without any recommendation (non-vaccinating). During 1999-2006, the overall seroprevalence of anti-HAV was 34.9% (95% confidence interval [CI] 33.1, 36.7). During 1999-2006, U.S.-born children living in vaccinating states (33.8%, 95% CI 26.2, 42.2) had a higher seroprevalence than children in non-vaccinating states (11.0%, 95% CI 9.4, 12.8; p < 0.001). Seroprevalence among children increased from 8.0% (95% CI 6.3, 10.1) during 1988-1994 to 20.2% (95% CI 16.0, 24.8) during 1999-2006 (p < 0.001). For U.S.-born children aged 6-19 years, the strongest factor associated with seroprevalence was residence in vaccinating states. Among U.S.-born adults aged > 19 years, the overall age-adjusted seroprevalence of anti-HAV was 29.9% (95% CI 28.3, 31.5) during 1999-2006, which was not significantly different from the seroprevalence during 1988-1994 (32.2%, 95% CI 30.1, 34.4). Increases in seroprevalence among children in vaccinating states suggest a positive effect of the 1999 vaccination recommendations.

Seroprevalence of antibody to mumps virus in the US population, 1999-2004.

In 2006, the largest mumps outbreak in the United States in 20 years occurred. To understand prior mumps seroprevalence and factors associated with the presence of antibody to mumps virus, data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES) were analyzed. A mumps virus-specific enzyme immunoassay was used to measure the seroprevalence of serum immunoglobulin G (IgG) antibody among NHANES participants aged 6-49 years. Participants were grouped on the basis of 10-year birth cohorts, 95% confidence intervals (CIs) were calculated using SUDAAN software, and logistic regression was used to identify independent predictors. The overall age-adjusted seroprevalence of IgG antibody to mumps virus during 1999-2004 was 90.0% (95% CI, 88.8%-91.1%). Seroprevalence was higher among US-born non-Hispanic blacks (96.4% [95% CI, 95.5%-97.2%]) and non-US-born Mexican Americans (93.7% [95% CI, 92.0%-95.2%]). Seroprevalence was significantly lower in the 1967-1976 birth cohort (85.7% [95% CI, 83.5%-87.8%]). The variables sex, education, and race/ethnicity/birthplace were independent predictors in at least 1 of the birth cohorts. The overall estimate of 90.0% is at the lower end of the estimated population immunity (90%-92%) needed to achieve herd immunity. Lower seroprevalence among groups suggest that they represent populations at an increased risk. For mumps control, high vaccine coverage and high population immunity must be achieved and maintained.