Age-stratified Seroprevalence Research Articles

Age-Stratified Seroprevalence of Respiratory Syncytial Virus: Analysis Using Prefusion F and G Protein Antibodies.

This is a cross-sectional serosurveillance study for RSV. Between June and September of 2021, a total of 150 sera were collected from 30 individuals in each age group (<5, 5-18, 19-49, 50-64, and ≥65 years). Seroprevalence was estimated using enzyme-linked immunosorbent assays targeting two stabilized prefusion F (preF; DS-Cav1 and SC-TM) and G proteins. The overall seroprevalence was low in young children and older adults, despite them having a higher risk of severe RSV infection. There was a remarkable difference in age-stratified seroprevalence rates between anti-preF and anti-G protein antibodies. Given the high disease burden and low seroprevalence in both infants and old adults, RSV vaccination would be crucial for pregnant women and people aged over 60 years.

Annual risk of hepatitis E virus infection and seroreversion: Insights from a serological cohort in Sitakunda, Bangladesh.

Hepatitis E virus (HEV) is a major cause of acute jaundice in South Asia. Gaps in our understanding of transmission are driven by non-specific symptoms and scarcity of diagnostics, impeding rational control strategies. In this context, serological data can provide important proxy measures of infection. We enrolled a population-representative serological cohort of 2,337 individuals in Sitakunda, Bangladesh. We estimated the annual risks of HEV infection and seroreversion both using serostatus changes between paired serum samples collected 9months apart, and by fitting catalytic models to the age-stratified cross-sectional seroprevalence. At baseline, 15% (95 CI: 14-17%) of people were seropositive, with seroprevalence highest in the relatively urban south. During the study, 27 individuals seroreverted (annual seroreversion risk: 15%, 95 CI: 10-21%), and 38 seroconverted (annual infection risk: 3%, 95CI: 2-5%). Relying on cross-sectional seroprevalence data alone, and ignoring seroreversion, underestimated the annual infection risk five-fold (0.6%, 95 CrI: 0.5-0.6%). When we accounted for the observed seroreversion in a reversible catalytic model, infection risk was more consistent with measured seroincidence. Our results quantify HEV infection risk in Sitakunda and highlight the importance of accounting for seroreversion when estimating infection incidence from cross-sectional seroprevalence data.

The burden of dengue in children and risk factors of transmission in nine districts in Sri Lanka

AbstractWe sought to understand the differences in age‐stratified seroprevalence rates in different regions in Sri Lanka to plan dengue vaccination programs, especially as the WHO has given guidance to vaccinate in high transmission settings. Age stratified seroprevalence rates were assessed in children, aged 10−20 years, in nine districts representing the nine provinces in Sri Lanka, from September 2022 to March 2023. A stratified multistage cluster was used to select 146 schools representing each district. Of the 5207 children recruited, the overall dengue seroprevalence rates in children was 24.8%, with the highest rates reported from Trincomalee (54.3%) and the lowest rates from Badulla (14.2%), which is a high‐altitude estate area. While the age‐stratified seroprevalence rates increased in some districts such as Trincomalee, Jaffna, Gampaha, and Ratnapura, which reported the highest seropositivity rates, there was no such increase with age in the other districts. There was a weak correlation between the dengue antibody positivity rates and age in most districts which had seroprevalence rates of &gt;25%, while there was no increase in antibody titers with age in the other districts. The seroprevalence rates was significantly higher in urban areas (35.8%) compared to rural (23.2%) and estate areas (9.4%), although there was no association with seropositivity rates with population density (Spearman's r = −0.01, p = 0.98), in each district. The seroprevalence rates in many districts were very different to those reported from Colombo, with many districts reporting low transmission rates. These data would be important to consider when rolling out dengue vaccines in Sri Lanka.

907. Age-stratified seroprevalence of respiratory syncytial virus in Korean population

Abstract Background Respiratory syncytial virus the two modified prefusion (preF) protein antigens (DS-Cav1 and SC-TM) and the fusion (G) protein, (RSV), a major childhood respiratory pathogen, is gaining attention as an important pathogen in adults also, especially in older people and the immunocompromised. Studies on RSV seroprevalence in the adult population are limited, even though it is important to know the level of preexisting immunity to RSV now that approval of RSV vaccines seems imminent. Therefore, we aimed to analyze antibody levels against RSV across age groups. *This study was funded by the grant of the Ministry of Food and Drug Safety of South Korea (21172MFDS179). Methods A total of 150 serum samples were collected from 30 subjects of each age group (under 5 years, 5–18 years, 19–49 years, 50–64 years, and ≥65 years). Considering higher RSV disease burden in infants than older children, children under 5 were further divided into two age groups including 0–12 months and 13–59 months. Age-stratified seroprevalence was estimated using ELISA targeting the two modified prefusion (preF) protein antigens (DS-Cav1 and SC-TM) and the fusion (G) protein, the major immunogens and popular vaccine targets. Seropositivity was determined based on the concentration of medium-titer RSV antiserum manufactured by the United States National Institute of Health. Results Antibody titers against SC-TM were similar across age groups. Antibody titers against DS-Cav1 were higher than those against SC-TM in all age groups except children aged 0–12 months. There was no significant difference in antibody titers between children aged 0–12 months and 13–59 months. Only about one fifth participants aged under 5 and over 65 were seropositive to RSV preF. Conclusion RSV seroprevalence was low overall. This study supports the importance of vaccination against RSV in infants and people over 65. Disclosures Hee Jin Cheong, M.D.,Ph.D., Sequiris: Advisor/Consultant

Seroprevalence of dengue virus infection in Pune City in India, 2019: A decadal change

BackgroundThe burden of dengue infection needs to be monitored along with tracking of the changes in dengue virus (DENV) transmission intensity for vaccine introduction decisions. MethodsThe seroprevalence of dengue was investigated in Pune City in India, in early 2019 using 1654 sera from apparently healthy human participants enrolled randomly through multistage cluster sampling. We used 797 retrospective human sera from late 2009 for comparison. All sera were assessed for the presence of dengue-specific IgG antibodies. A subset (n = 230) was tested for serotype-specific plaque reduction-neutralizing antibodies against all four serotypes. ResultsThe dengue IgG seroprevalence of 62.9% (95% CI 59.4–66.1) in 2009 increased to 88.4% (95% CI 86.8–89.8) in 2019. Age-stratified dengue seroprevalence revealed a gradual increase in IgG seropositivity from 70.1% in 0–9 years to 85.0% in 10–19 years. The annual probability of dengue infection estimated as a force of infection was 4.1 (95% CI 3.8–4.5) in 2009, which increased to 10.9 (95% CI 10.2–11.6) in 2019. Analysis of dengue serotype-specific neutralizing antibodies revealed DENV-3 as the dominant serotype. The age of exposure to at least one dengue serotype was reduced in 2019 over 2009. ConclusionsThere was a significant increase in the intensity of dengue virus transmission in Pune City over the decade. Since over 85% of the participants above nine years of age had exposure to DENV by 2019, dengue vaccine introduction can be considered. Moreover, such repeated serosurveys in different regions might inform about the readiness of the population for dengue vaccination.

Large Diffusion of Severe Acute Respiratory Syndrome Coronavirus 2 After the Successive Epidemiological Waves, Including Omicron, in Guinea and Cameroon: Implications for Vaccine Strategies.

We aimed to estimate the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence among the general population in Conakry, Guinea and Yaounde, Cameroon after the coronavirus disease 2019 Omicron wave. We conducted population-based, age-stratified seroprevalence surveys in Conakry and Yaounde (May and June 2022). We collected demographic and epidemiologic information and dried blood spot samples that were tested for SARS-CoV-2 immunoglobulin G (IgG) antibodies using recombinant nucleocapsid and spike proteins with Luminex technology. Samples were obtained from 1386 and 1425 participants in Guinea and Cameroon, respectively. The overall age-standardized SARS-CoV-2 IgG seroprevalence against spike and nucleocapsid proteins was 71.57% (95% confidence interval [CI], 67.48%-75.33%) in Guinea and 74.71% (95% CI, 71.99%-77.25%) in Cameroon. Seroprevalence increased significantly with age categories. Female participants were more likely than male participants to be seropositive. The seroprevalence in unvaccinated participants was 69.6% (95% CI, 65.5%-73.41%) in Guinea and 74.8% (95% CI, 72.04%-77.38%) in Cameroon. In multivariate analysis, only age, sex, and education were independently associated with seropositivity. These findings show a high community transmission after the different epidemiological waves including Omicron, especially among people aged >40 years. In addition, our results suggest that the spread of SARS-CoV-2 has been underestimated as a significant proportion of the population has already contracted the virus and that vaccine strategies should focus on vulnerable populations.

Age-Stratified Seroprevalence of SARS-CoV-2 Antibodies before and during the Vaccination Era, Japan, February 2020-March 2022.

Japan has reported a relatively small number of COVID-19 cases. Because not all infected persons receive diagnostic tests for COVID-19, the reported number must be lower than the actual number of infections. We assessed SARS-CoV-2 seroprevalence by analyzing >60,000 samples collected in Japan (Tokyo Metropolitan Area and Hokkaido Prefecture) during February 2020-March 2022. The results showed that ≈3.8% of the population had become seropositive by January 2021. The seroprevalence increased with the administration of vaccinations; however, among the elderly, seroprevalence was not as high as the vaccination rate. Among children, who were not eligible for vaccination, infection was spread during the epidemic waves caused by the SARS-CoV-2 Delta and Omicron variants. Nevertheless, seroprevalence for unvaccinated children <5 years of age was as low as 10% as of March 2022. Our study underscores the low incidence of SARS-CoV-2 infection in Japan and the effects of vaccination on immunity at the population level.

Age-stratified infection fatality rate of COVID-19 in the non-elderly population

The largest burden of COVID-19 is carried by the elderly, and persons living in nursing homes are particularly vulnerable. However, 94% of the global population is younger than 70 years and 86% is younger than 60 years. The objective of this study was to accurately estimate the infection fatality rate (IFR) of COVID-19 among non-elderly people in the absence of vaccination or prior infection. In systematic searches in SeroTracker and PubMed (protocol: https://osf.io/xvupr), we identified 40 eligible national seroprevalence studies covering 38 countries with pre-vaccination seroprevalence data. For 29 countries (24 high-income, 5 others), publicly available age-stratified COVID-19 death data and age-stratified seroprevalence information were available and were included in the primary analysis. The IFRs had a median of 0.034% (interquartile range (IQR) 0.013–0.056%) for the 0–59 years old population, and 0.095% (IQR 0.036–0.119%) for the 0–69 years old. The median IFR was 0.0003% at 0–19 years, 0.002% at 20–29 years, 0.011% at 30–39 years, 0.035% at 40–49 years, 0.123% at 50–59 years, and 0.506% at 60–69 years. IFR increases approximately 4 times every 10 years. Including data from another 9 countries with imputed age distribution of COVID-19 deaths yielded median IFR of 0.025–0.032% for 0–59 years and 0.063–0.082% for 0–69 years. Meta-regression analyses also suggested global IFR of 0.03% and 0.07%, respectively in these age groups. The current analysis suggests a much lower pre-vaccination IFR in non-elderly populations than previously suggested. Large differences did exist between countries and may reflect differences in comorbidities and other factors. These estimates provide a baseline from which to fathom further IFR declines with the widespread use of vaccination, prior infections, and evolution of new variants.

SARS-CoV-2 infection and antibody seroprevalence in routine surveillance patients, healthcare workers and general population in Kita region, Mali: an observational study 2020–2021

ObjectiveTo estimate the degree of SARS-CoV-2 transmission among healthcare workers (HCWs) and general population in Kita region of Mali.DesignRoutine surveillance in 12 health facilities, HCWs serosurvey in five health facilities...

Decadal Change in Seroprevalence of Chikungunya Virus Infection in Pune City, India.

Chikungunya virus (CHIKV) is an arthropod-borne virus capable of causing large outbreaks. We aimed to determine the decadal change in the extent of chikungunya virus infection from 2009 to 2019. We implemented a prospective cross-sectional survey in Pune City using a 30-cluster approach with probability-proportion-to-size (PPS) sampling, with blood samples collected from 1654 participants in early 2019. The study also included an additional 799 blood samples from an earlier serosurvey in late 2009. The samples were tested by an in-house anti-CHIKV IgG ELISA assay. The overall seroprevalence in 2019 was 53.2% (95% CI 50.7–55.6) as against 8.5% (95% CI 6.5–10.4) in 2009. A fivefold increase in seroprevalence was observed in a decade (p < 0.00001). The seroprevalence increased significantly with age; however, it did not differ between genders. Modeling of age-stratified seroprevalence data from 2019 coincided with a recent outbreak in 2016 followed by the low-level circulation. The mean estimated force of infection during the outbreak was 35.8% (95% CI 2.9–41.2), and it was 1.2% after the outbreak. To conclude, the study reports a fivefold increase in the seroprevalence of chikungunya infection over a decade in Pune City. The modeling approach considering intermittent outbreaks with continuous low-level circulation was a better fit and coincided with a recent outbreak reported in 2016. Community engagement and effective vector control measures are needed to avert future chikungunya outbreaks.

Dynamic Features of Herd Immunity: Similarities in Age-Specific Anti-Measles Seroprevalence Data between Two Countries of Different Epidemiological History.

(1) Background: Measles immunization gap(s) raise the concern of potential outbreaks. Both Croatia and Hungary are situated in the vicinity of measles-endemic countries. Potentially compromised immunization activities due to the COVID-19 surge is a ground for concern. Our aim was to compare age-stratified seroprevalence results in the cross-border region. (2) Methods: Anti-MMR specific antibody levels (IgG) of 950 anonymous Croatian samples were compared with previous Hungarian results (n > 3500 samples), and former Croatian seroprevalence data (n = 1205). Seropositivity ratios were determined using our self-developed anti-MMR indirect ELISA (Euroimmun IgG ELISA kits were used as control). (3) Results: Measured seropositivity ratios of the Croatian samples were largely overlapping with our earlier published Hungarian data (the lowest seropositivity ratios were measured among individuals of 34–43 years of age with 78% of seropositivity) and are in accordance with earlier published data of Croatian researchers. (4) Conclusion: Although the epidemiological histories of the two countries are different, analogies in age-specific measles susceptibility have been discovered. We suggest that besides the potential coincidence in vaccination ineffectiveness, the inherent biological dynamics of vaccination-based humoral protection might have also contributed to the experienced similarities. Our findings may also serve as a lesson regarding the current anti-COVID-19 vaccination strategy.

The seroprevalence, waning rate, and protective duration of anti-diphtheria toxoid IgG antibody in Nha Trang, Vietnam

Background: Diphtheria cases reported in Central Vietnam since 2013 were mainly in children aged 6-15 years, which may reflect an immunity gap. There is little information on population immunity against diphtheria in countries without a school-entry booster dose. We aimed to measure the age-stratified seroprevalence of anti-diphtheria toxoid antibodies, quantify the change in antibody levels in individuals over time, and estimate the length of protective immunity after vaccination in well-vaccinated communities in Vietnam.Methods: An age-stratified seroprevalence survey among individuals aged 0-55 years was conducted at Nha Trang, Vietnam. The same participants were followed up after two years to quantify the change in antibody levels. IgG was measured using ELISA. The length of protective immunity after vaccination was estimated using a mixed-effect linear regression model with random intercept.Results: Overall seroprevalence was 26% (95%CI:20-32%). Age-stratified seroprevalence was 68% (95%CI:4-11%), 7% (95%CI:4-11%), 12% (95%CI:7-19%), 33% (95%CI:27-40%), and 28% (95%CI:17-43%) among those aged ≤5, 6-15,16-25, 26-35, and 36-55 years, respectively. The antibody levels declined by 47% (95%CI:31-59%) over two years, and the predicted duration of vaccine-derived protective immunity after receiving four doses was 4.3 years (95%CI:3.5–5.3) among participants aged six years or younger.Conclusion: Given the low seroprevalence and short period of vaccine protection, a school-entry booster dose (5-7 years) is recommended in Vietnam.

Superinfection of other hepatitis viruses on top of chronic hepatitis B: The more, the worse

Superinfection of other hepatitis viruses on top of chronic hepatitis B: The more, the worse

Seroprevalence of SARS-CoV-2 antibodies in university students: Cross-sectional study, December 2020, England

BackgroundIn England, the reopening of universities in September 2020 coincided with a rapid increase in SARS-CoV-2 infection rates in university aged young adults. This study aimed to estimate SARS-CoV-2 antibody prevalence in students attending universities that had experienced a COVID-19 outbreak after reopening for the autumn term in September 2020.MethodsA cross-sectional serosurvey was conducted during 02–11 December 2020 in students aged ≤ 25 years across five universities in England. Blood samples for SARS-CoV-2 antibody testing were obtained using a self-sampling kit and analysed using the Abbott SARS-CoV-2 N antibody and/or an in-house receptor binding domain (RBD) assay.FindingsSARS-CoV-2 seroprevalence in 2,905 university students was 17.8% (95%CI, 16.5–19.3), ranging between 7.6%-29.7% across the five universities. Seropositivity was associated with being younger likely to represent first year undergraduates (aOR 3.2, 95% CI 2.0–4.9), living in halls of residence (aOR 2.1, 95% CI 1.7–2.7) and sharing a kitchen with an increasing number of students (shared with 4–7 individuals, aOR 1.43, 95%CI 1.12–1.82; shared with 8 or more individuals, aOR 1.53, 95% CI 1.04–2.24). Seropositivity was 49% in students living in halls of residence that reported high SARS-CoV-2 infection rates (>8%) during the autumn term.InterpretationDespite large numbers of cases and outbreaks in universities, less than one in five students (17.8%) overall had SARS-CoV-2 antibodies at the end of the autumn term in England. In university halls of residence affected by a COVID-19 outbreak, however, nearly half the resident students became infected and developed SARS-CoV-2 antibodies.

Age-stratified seroprevalence of vaccine-preventable infectious disease in Saravan, Southern Lao People’s Democratic Republic

BackgroundLao People’s Democratic Republic has frequent outbreaks of vaccine-preventable diseases (VPD). This study aimed to determine susceptibility and exposure to VPD in Saravan, a rural province with high ethnic diversity and some of the poorest health indicators nationwide. MethodsPatients from three district hospitals and one provincial hospital were enrolled. Serum was tested by ELISA for IgG against hepatitis B virus (HBV), tetanus, diphtheria, measles, and rubella. ResultsThe study enrolled 2463 participants aged 5–90 years. Exposure to HBV was 33.2% and increased with age up to 62.4% of those aged >50 years. HBV surface antigen prevalence was 5.7% in males and 2.4% in females; 9.9% had serology compatible with vaccination. Seroprevalence of protective anti-tetanus antibodies was 46.3% overall. Protective anti-diphtheria seroprevalence was 40.5%. Anti-measles seroprevalence increased from 16.7% in those aged 5–10 years to 97.7% in those aged >50 years. Anti-rubella seroprevalence was 93.0% overall. There were differences in seroprevalences between sex, districts and ethnicity. ConclusionsRoutine infant vaccination needs strengthening in order to close the immunity gaps. High burden of HBV infection should be addressed by increasing birth dose vaccine coverage. Regional and ethnic differences need to be investigated to enable a targeted approach to vaccination.

Monitoring the proportion of the population infected by SARS-CoV-2 using age-stratified hospitalisation and serological data: a modelling study

BackgroundRegional monitoring of the proportion of the population who have been infected by SARS-CoV-2 is important to guide local management of the epidemic, but is difficult in the absence of regular nationwide serosurveys. We aimed to estimate in near real time the proportion of adults who have been infected by SARS-CoV-2.MethodsIn this modelling study, we developed a method to reconstruct the proportion of adults who have been infected by SARS-CoV-2 and the proportion of infections being detected, using the joint analysis of age-stratified seroprevalence, hospitalisation, and case data, with deconvolution methods. We developed our method on a dataset consisting of seroprevalence estimates from 9782 participants (aged ≥20 years) in the two worst affected regions of France in May, 2020, and applied our approach to the 13 French metropolitan regions over the period March, 2020, to January, 2021. We validated our method externally using data from a national seroprevalence study done between May and June, 2020.FindingsWe estimate that 5·7% (95% CI 5·1–6·4) of adults in metropolitan France had been infected with SARS-CoV-2 by May 11, 2020. This proportion remained stable until August, 2020, and increased to 14·9% (13·2–16·9) by Jan 15, 2021. With 26·5% (23·4–29·8) of adult residents having been infected in Île-de-France (Paris region) compared with 5·1% (4·5–5·8) in Brittany by January, 2021, regional variations remained large (coefficient of variation [CV] 0·50) although less so than in May, 2020 (CV 0·74). The proportion infected was twice as high (20·4%, 15·6–26·3) in 20–49-year-olds than in individuals aged 50 years or older (9·7%, 6·9–14·1). 40·2% (34·3–46·3) of infections in adults were detected in June to August, 2020, compared with 49·3% (42·9–55·9) in November, 2020, to January, 2021. Our regional estimates of seroprevalence were strongly correlated with the external validation dataset (coefficient of correlation 0·89).InterpretationOur simple approach to estimate the proportion of adults that have been infected with SARS-CoV-2 can help to characterise the burden of SARS-CoV-2 infection, epidemic dynamics, and the performance of surveillance in different regions.FundingEU RECOVER, Agence Nationale de la Recherche, Fondation pour la Recherche Médicale, Institut National de la Santé et de la Recherche Médicale (Inserm).

The interplay between COVID-19 restrictions and vaccination

Lancet Infectious Diseases, The - Sous presse. Epreuves corrigees par l'auteur. Disponible en ligne depuis le jeudi 1 avril 2021

Monitoring the Proportion Infected by SARS-CoV-2 from Age-Stratified Hospitalisation and Serological Data

Background: Regional monitoring of the proportion infected by SARS-CoV-2 is important to guide local management of the epidemic, but is difficult in the absence of regular nationwide serosurveys. Methods: We developed a method to reconstruct in real-time the proportion infected by SARS-CoV-2 and the proportion of infections being detected from the joint analysis of age-stratified seroprevalence, hospitalisation and case data. We applied our approach to the 13 French metropolitan regions. Findings: We estimate that 5.7% [5.1%-6.4%] of adults in metropolitan France had been infected by SARS-CoV-2 by May 2020. This proportion remained stable until August and increased to 12.6% [11.2%-14.3%] by the end of November. With 23.8% [21.2%-26.8%] infected in the Paris region compared to 4.0% [3.5% - 4.6%] in Brittany, regional variations remained large (Coefficient of Variation CV: 0.53) although less so than in May (CV: 0.74). The proportion infected was twice higher (17.6% [13.4%-22.7%]) in 20-49 y.o. than in 50+ y.o (8.0% [5.7% - 11.5%]). Forty percent [33.7% - 45.4%] of infections in adults were detected in June-August compared to 55.7% [48.7% - 63.1%] in September-November. Our method correctly predicted seroprevalence in 11 regions in which only hospitalisation data were used. Interpretation: In the absence of contemporary serosurvey, our real-time monitoring indicates that the proportion infected by SARS-CoV-2 may be above 20% in some French regions. Funding Statement: EU RECOVER, ANR, Fondation pour la Recherche Medicale, Inserm. Declaration of Interests: Prof Fabrice Carrat reports personal fees from Imaxio and Sanofi, outside the submitted work. The other authors declare no competing interests.

Hepatitis A Virus in Lao People's Democratic Republic: Seroprevalence and Risk Factors.

Despite several recent reports of outbreaks of hepatitis A, little is known about the disease burden in Lao People's Democratic Republic (PDR). We conducted a cross-sectional age-stratified seroprevalence study of anti-hepatitis A virus (HAV) IgG and risk factors in a rural province (Xiengkhouang) and Vientiane capital in Lao PDR. Overall, 62% of participants were anti-HAV positive in Xiengkhouang Province compared with 45.5% in Vientiane capital. In Xiengkhouang, 23.7% of 5- to 10-year-olds were already seropositive compared with 5% in Vientiane. A dramatic increase in seroprevalence occurred between 15- to 20-year and 21- to 30-year age-groups (35.7-62.4%, Xiengkhouang, and 11.5-69.7%, Vientiane) until essentially all older adults were positive in both locations. The main risk factors for HAV antibodies were age, non-Lao-Tai ethnicity, and food-related risk factors. In conclusion, Lao children seem to be exposed very early to HAV, particularly in rural settings, and exposure continues throughout their lives, mostly without being reported. In the older birth cohorts, the high seroprevalence may largely reflect poor sanitation and exposure during childhood. In Vientiane capital, the lower seroprevalence at young ages may reflect better water sanitation since the late 1990s. A comparison with neighboring Thailand indicates that the impact of improved sanitation in Lao PDR began only two decades later. Further improvements in water sanitation, in particular in the rural districts, and better food hygiene are warranted. Our study also suggests that HAV infections are underreported. Improved reporting would provide guidance for targeted interventions to further reduce HAV infections.

Epstein-Barr Virus Seroprevalence and Force of Infection in a Multiethnic Pediatric Cohort, Singapore.

Epstein-Barr virus (EBV) spreads through bodily fluids, especially saliva, and can cause infectious mononucleosis. EBV immunity and infection status can be assessed by testing EBV viral capsid antigen and nuclear antigen (EBNA) antibodies in blood. In this study, we investigated the seroprevalence and force of infection (FOI) of EBV antibodies among children and young people in 3 ethnic groups in Singapore. Eight hundred ninety-six residual serum samples at a tertiary hospital were tested for viral capsid antigen (IgG and IgM) and EBNA IgG antibodies using Abbott Architect assays. We calculated the EBV seroprevalence using catalytic models to estimate the EBV force of infection from age-stratified seroprevalence data, both overall and by ethnic group. Overall seropositivity was 68.3% (n = 612). Seropositivity was higher in Malays (81.8%) compared with both Chinese (64.2%) and Indians (58.4%). EBV FOI was consistently higher in Malays, with an estimated annual rate of seroconversion of 25% in children 1 year, of age compared with 14% among Chinese and Indians at the same age. The seroprevalence patterns of EBV antibodies in the Chinese and Indian, but not Malay children in Singapore by 19 years of age resemble those previously reported in developed countries. Ideally, any future EBV vaccination strategy would need to target infants <1 year of age for maximum population benefit.