Prevalence of anti-hepatitis A antibodies in an urban middle class area of Argentina: some associated factors

Seroprevalence of hepatitis A virus among people born before and after implementation of universal vaccination in Argentina

BACKGROUND

Until 2005, when a single dose of vaccine was implemented in one-year-old children, the Hepatitis A virus (HAV) was responsible for approximately 90% of acute hepatitis cases in the paediatric population in Argentina. However, despite vaccination success, sporadic outbreaks of HAV still occur among adults. This study aimed to assess the seroepidemiology of HAV in Argentina, analysing IgG and IgM antibodies against HAV in a large population, both vaccinated and unvaccinated.

METHODS

The study included 16,982 patients attending a hospital from 2001 to 2023. The cohort was divided into two groups: 16,638 individuals who were not reached by the vaccination program implemented in 2005 and 344 children who were covered by the universal vaccination.

RESULTS

Anti-HAV IgG was detected in 56.7% of cases. The rate was significantly higher in individuals born after 2005 (77.7%) compared to those born before (56.3%), p < 0.001. The age groups 19-40 and 41-60 years showed the anti-HAV IgG lowest rates. On the other hand, 100/3956 cases (2.5%) with suspected acute hepatitis were positive for Anti-HAVIgM. Notably, none of these were born after the mandatory vaccine rollout.

CONCLUSIONS

The study of this large cohort contributes to the understanding of the seroepidemiology of HAV. Although the implementation of the vaccine achieved its main goal, the age segment between 19 and 60 years does not reach the estimated threshold to achieve herd immunity. These findings reveal the importance of targeting vaccination campaigns, provide essential insights for public health planning, and guide future immunisation strategies against HAV in Argentina.

Seroprevalence of hepatitis A virus infection in Central-West of Tunisia

Hepatitis A infections still represent a major global health concern. During the past years, a transition pattern of the hepatitis A epidemiology was noted in many parts of the world. In Tunisia, there is not a recent survey on age-specific hepatitis A virus seroprevalence. This study aimed to investigate the seroprevalence of hepatitis A virus infection in Central-West Tunisia, representative of regions with lowest socioeconomic level in the country, before vaccine implementation. Sera obtained from the blood samples of subjects were screened for the detection of hepatitis A virus. The seroprevalence was evaluated by detection of total antibodies to hepatitis A virus using commercially available immunoassay kits. A total of 1379 subjects, aged 5-75 years (mean age: 29.0 ± 17.3 years) were studied. The global anti-hepatitis A virus seroplevalence was 84.7% (95% confidence interval: [82.6-86.5]). A higher hepatitis A virus seroprevalence was showed in subjects aged 10-14 years compared to those aged less than 10 years (50.0% vs. 31.0%). In subjects aged 20-29 years, a rapid increase in the hepatitis A virus prevalence was noted; it reached 97.0%. The seroprevalence of anti-hepatitis A virus differed by zone of residence (81.1% in rural area vs. 72.4% in urban area, p = .005) and increased significantly with lower level of education (p = .019). There was no statistical significant seroprevalence difference between male and female: 84.2% versus 85.2%, respectively. Our study confirm the transition pattern of the hepatitis A virus endemicity in Tunisia from high to intermediate and provide an evaluation of the hepatitis A virus epidemiological situation before vaccine implementation.

Single-Dose Universal Hepatitis A Immunization in Argentina: Low Viral Circulation and High Persistence of Protective Antibodies Up to 4 Years

BACKGROUND

Single-dose hepatitis A virus (HAV) vaccination was implemented in all Argentinean children aged 12 months in 2005. Between 2005 and 2011, a dramatic decline was observed in HAV infection rates, fulminant hepatitis, and liver transplantation. This study assessed current viral circulation and estimated protective antibody persistence 4 years after vaccination.

METHODS

Prevalence of prevaccination anti-HAV antibodies in 12-month-old children was evaluated as an indirect estimation of viral circulation (Group A). Seroprevalence was also measured in 5-year-old children who received 1 dose of HAV vaccine at 1 year of age (Group B). Blood samples were tested for immunoglobulin (Ig)G anti-HAV antibodies (seroprotection = ≥10 mIU/mL). All Group A-positive samples were tested for IgM anti-HAV antibodies to identify recent infections. Logistic regression analysis was done to evaluate associations between demographic and socioeconomic variables and seroprotection.

RESULTS

Of 433 children from Group A, 29.5% (95% confidence interval [CI], 25.2-33.8) were positive for IgG anti-HAV antibodies with a geometric mean concentration (GMC) of 6.17 mIU/mL (95% CI, 5.33-7.15 mIU/mL); all IgM anti-HAV were negative. From 1139 in Group B, 93% (95% CI, 91.7-94.6) maintained seroprotection with a GMC of 97.96 mIU/mL (95% CI, 89.21-107.57 mIU/mL). Kindergarten attendance was associated with seroprotection in Group B (odds ratio [OR], 2.0; 95% CI, 1.26-3.3). In contrast, high maternal educational level was associated with a lack of seroprotection in this group (OR, .26; 95% CI, .09-.8).

CONCLUSIONS

Single-dose, universal hepatitis A immunization in infants resulted in low HAV circulation and persistent immunologic protection up to 4 years in Argentina. Variables associated with presence or absence of seroprotection in vaccinated children could be related to differences in hygiene habits in settings with residual viral circulation.

Evidence of hepatitis A virus circulation in central Argentina: seroprevalence and environmental surveillance

BACKGROUND

Hepatitis A virus (HAV) has shown intermediate endemicity in Argentina, but notification of clinical cases has decreased since the introduction of the vaccine in 2005.

OBJECTIVES

In order to get insight into the local circulation of this virus after four years of the official introduction of the vaccine, the aims of this study were to provide information on HAV immune status of the adult population of Córdoba city and to conduct environmental surveillance of HAV in sewage and river samples in the same region.

STUDY DESIGN

The prevalence of anti-HAV was determined by EIA in 416 samples of people (without prior vaccination) from Córdoba city (2009-2010). Spline regression models were estimated under generalized additive models. Environmental surveillance was conducted in river and sewage samples collected in the same period. Viral detection was performed by RT-Nested PCR of the 5'UTR.

RESULTS

In Córdoba, the global prevalence of anti-HAV was 73.5%. It increased with age (p<0.0001) and it was associated with the low-income population (OR: 1.14; 95% CI 1.05-1.25). This prevalence decreased in younger age groups, especially in the high-income population. Environmental monitoring revealed the presence of HAV (IA) in 20.8% and 16.1% of wastewater and river samples, respectively.

CONCLUSIONS

As a consequence of a decrease in HAV circulation due to improvements in immunization, socio-economic and hygienic conditions, young adults are becoming increasingly susceptible to HAV infections. Environmental monitoring demonstrated that HAV circulates in the local population; therefore, health care systems should consider the implementation of preventive measures for susceptible adults in order to reduce the risk of HAV infection.

Co-circulation of genotypes IA and IB of hepatitis A virus in Northeast Brazil

The Northeast region is the location of most cases of acute hepatitis A virus (HAV) in Brazil. In the present study, the genotypes of HAV strains from Pernambuco State, one of most populous states in the Northeast region, were characterized. Blood samples positive for anti-HAV IgM from 145 individuals (mean age = 29.1 years), collected during 2002 and 2003, were submitted to nested RT-PCR for amplification of the 5'non-translated region (5'NTR) and VP1/2A regions of the HAV genome. The VP1/2A and 5'NTR regions were amplified in 39 and 21% of the samples, respectively. Nucleotide sequencing was carried out in 46% of VP1/2A and in 53% of 5'NTR isolates. The identity in nucleotide sequence of the VP1/2A region ranged from 93.6 to 100.0%. Phylogenetic analysis of the VP1/2A sequences showed that 65% belong to sub-genotype IA and 35% to sub-genotype IB. Co-circulation of both sub-genotypes was observed in the two years studied. Distinct clusters of highly related sequences were observed in both sub-genotypes, suggesting endemic circulation of HAV strains in this area. In the 5'NTR isolates, 92.7-99.2% identity was observed and two isolates presented one deletion at position 413. Phylogenetic analysis showed that genotype IA strains cluster in the tree in the same way as genotype IB strains, but one IIIA isolate from Spain clusters with genotype IB strains. These results do not allow us to state that 5'NTR could be used to genotype HAV sequences. This is the first report of co-circulation of sub-genotypes IA and IB in this region, providing additional information about the molecular epidemiology of HAV strains in Brazil.

The effects of socioeconomic development on worldwide hepatitis A virus seroprevalence patterns

BACKGROUND

Hepatitis A virus (HAV) infection confers long-term immunity, so mathematical analysis of age-specific seroprevalence in populations can reveal changes in the infection rate over time. HAV transmission is related to access to clean drinking water, personal hygiene and public sanitation.

METHODS

We used an SIR (susceptible-infectious-recovered) compartmental model with age structure to fit a time-dependent logistic function for HAV force of infection for 157 published age-seroprevalence data sets. We then fit linear regression models for socioeconomic variables and infection rate.

RESULTS

The proportion of the population with access to clean drinking water, the value of the human development index (HDI), and per capita gross domestic product (GDP) are all inverse predictors of HAV infection rates. Declining infection rates were observed in 65.6% of the surveys. Discussion This work demonstrates the utility of HAV seroprevalence studies to reveal patterns of change in force of infection and to assess the association between socioeconomic risk factors and transmission rates.

Overlapping epidemiologies of hepatitis A and typhoid fever: the needs of the traveler

Hepatitis A and typhoid fever are endemic infectious diseases in many parts of the world. They share a common, simple mode of transmission--the fecal--oral route-associated with poor hygiene. The low endemicity of both diseases in developed countries, and the rise in travel to exotic destinations for business and leisure, mean that increasing numbers of travelers are being exposed to infection. Effective, established vaccines are available against both diseases, and recently new formulations combining both vaccines in one injection have been licensed. We review the present epidemiologic situation for both diseases, to determine the necessity to routinely vaccinate travelers against both diseases.

Loss of hepatitis A virus (HAV) antibodies after peripheral stem cell transplantation (PSCT)

The majority of patients with hepatitis A have a benign course, but some may develop fulminant hepatitis and hematological complications. Peripheral stem cell transplantation (PSCT) is associated with loss of immunity. There are no data regarding loss of HAV antibodies (anti-HAV) after PSCT. We retrospectively evaluated the persistence of anti-HAV in a nonvaccinated population that underwent PSCT. Serum detection of anti-HAV was determined before and after PSCT using a qualitative commercially available enzyme immunoassay. From January 1997 to March 2001, 136 (68%) of 201 patients tested (+) for anti-HAV prior to PSCT. Subsequent investigation of anti-HAV was possible in 36 of these patients at a median of 12 months after PSCT. The median age of patients was 47 years old; they had diagnoses of hematological malignancies (33) and solid tumors (three), and underwent autologous (31) and allogenic (five) PSCT. A total of 31 (86%) of 36 patients remained anti-HAV (+) and five (14%) became (-) after PSCT. The variables age, sex, diagnosis, type of PSCT, time of testing, and number of CD34 cells infused were not predictors of loss of anti-HAV. In conclusion, 14% of 36 nonvaccinated anti-HAV (+) patients lost their antibodies at a median of 12 months after PSCT.

Empiric immunization versus serologic screening: developing a cost-effective strategy for the use of hepatitis A immunization in travelers

BACKGROUND

Older individuals and those born overseas are thought at increased risk of prior exposure and thus have naturally acquired immunity to hepatitis A. Whether these individuals or other groups of international travelers should be screened for acquired immunity or empirically immunized is not clear. Hepatitis A serology and risk factor data was obtained prospectively in patients presenting for hepatitis A immunization and used to develop a cost-effective strategy for the use of serologic screening and empiric immunization in our traveler population.

METHOD

Candidates for hepatitis A immunization were routinely screened for total hepatitis A serum antibody. Risk factor data including country of birth, travel history, and history of jaundice was collected. Cost-effectiveness was assessed by comparing the cost of serology to screen all patients plus cost to immunize those found to be seronegative with, the cost of empirically immunizing all patients.

RESULTS

Analyses were conducted comparing age, travel history, country of birth, and history of jaundice for significance in predicting seropositivity in a group of 115 subjects. Country of birth was statistically a significant predictor of positive results with 80.0% of foreign-born patients positive for total antibody against hepatitis A compared with 35.6% of patients born in the United States. Living outside of the United States (defined as greater than 30 days) was also correlated with a higher prevalence of hepatitis A positive serology. Age was not predictive for the group as a whole. A lower prevalence (24.3%) was noted in the group of US born individuals aged 30 to 60. Travel and prior history of jaundice failed to demonstrate significance.

CONCLUSIONS

Employing a simple cost-effectiveness equation using cost of serological testing, cost of vaccine, and prevalence of acquired immunity in the community, a strategy was developed. In our population it was cost-effective to screen all foreign-born individuals and those who had lived outside the United States.