Hepatitis A and B in children and adolescents--what can we learn from Puglia (Italy) and Catalonia (Spain)?

Hepatitis a Vaccine as Opportunity of Primary Prevention for Food Handlers: A Narrative Review

The hepatitis A virus (HAV) is still a leading cause of viral hepatitis worldwide. After a long incubation period, the clinical manifestations range from asymptomatic infection to acute liver failure. The severity of the disease increases with age and pre-existing liver disease. The transmission is mainly via person-to-person contact or ingestion of contaminated food or water. Food contamination can occur at any step of the food chain, especially when infected people handle not-heated or otherwise-treated food. HAV is endemic in low-income countries because of poor sanitary and sociodemographic conditions. The populations of developed countries are highly susceptible, and large outbreaks occur when HAV is introduced from endemic countries due to globalization, travel, and movement of foodstuffs. HAV prevention includes hygiene practices, immunoglobulins, and vaccination. Safe and effective inactivated and live attenuated vaccines are available and provide long-term protection. The vaccine targets are children and subjects at increased risk of HAV exposure or serious clinical outcomes. This review discusses the critical role of food handlers in the spread of HAV and the opportunity for food industry employers to consider food handler immunization a tool to manage both food safety in compliance with HACCP principles and food operators' biologic risk.

A Study of Hepatitis A Seroprevalence in a Paediatric and Adolescent Population of the Province of Florence (Italy) in the Period 2017-2018 Confirms Tuscany a Low Endemic Area

Background: Italy is considered an area with very low HAV (hepatitis A virus) endemicity. Currently in Italy the anti-HAV vaccine is recommended only for specific risk groups and there is no universal vaccination program. The aim of this study was to assess the level of immunity against hepatitis A in a sample of children and adolescents from the province of Florence. Methods: A total of 165 sera were collected from subjects aged 1 to 18 years, proportionally selected according to the general population size and stratified by age and sex. A qualitative evaluation of anti-HAV antibodies was performed using the enzyme-linked immunosorbent assay (ELISA). Anamnestic and vaccination status data were also collected. Results: Our study showed a hepatitis A seroprevalence of 9.1% in the enrolled population. A statistically significant difference in the prevalence of anti-HAV was found between Italian and non-Italian subjects. About half of the population having anti-HAV antibodies was reported to be vaccinated, and no cases of hepatitis A were found. Conclusions: The data from our study confirmed Tuscany as an area with low HAV endemicity and showed that hepatitis A seroprevalence is significantly higher in foreign children and adolescents. The presence of more seropositive subjects than those vaccinated was probably due to a natural immunization achieved through a subclinical infection and/or to underreporting of the surveillance systems.

Changes in seroprevalence of hepatitis A after the implementation of universal childhood vaccination in Shandong Province, China: A comparison between 2006 and 2014

OBJECTIVES

The hepatitis A vaccine (HepA) has been included in the national expanded program on immunization (EPI) in China since 2008. This study was performed to evaluate the change in dynamics of the seroepidemiology of hepatitis A virus (HAV) before and after the introduction of the program.

METHODS

The trends in seroepidemiology of anti-HAV antibodies were examined in Shandong Province, China, drawing on two population-based samples of persons aged 1-59 years, one obtained in the year 2006 (n = 6682) and the other in 2014 (n = 5095).

RESULTS

A dramatic increase in seroprevalence of anti-HAV antibodies from 30.76% (95% confidence interval (CI) 26.24-35.28%) to 77.46% (95% CI 74.04-80.87%) among children aged 1.5-7 years (born after HepA was recommended for routine childhood immunization), as well as an increase from 35.32% (95% CI 29.31-41.33%) to 66.69% (95% CI 55.59-77.80%) in subjects aged 8-14 years, was observed in 2014 when compared with 2006. By contrast, a decline in seroprevalence among subjects aged 15-29 years, as seen particularly in those 20-29 years of age, from 85.72% (95% CI 80.29-91.14%) to 69.24% (95% CI 62.02-76.45%), was found in this study. There was no statistically significant difference in seroprevalence between 2006 and 2014 among the subjects older than 30 years of age.

CONCLUSIONS

The national HepA routine immunization program has had a positive effect, leading to an increase in anti-HAV seroprevalence among children in Shandong Province, China. More attention should be paid to young adults in the province.

Immunization against Hepatitis A

Worldwide, there are multiple formaldehyde-inactivated and at least two live attenuated hepatitis A vaccines now in clinical use. The impressive immunogenicity of inactivated vaccines is reflected in rapid seroconversion rates, enabling both preexposure and postexposure prophylaxis. Universal childhood vaccination programs targeting young children have led to significant drops in the incidence of hepatitis A both in toddlers and in susceptible nonimmune adults in regions with intermediate endemicity for hepatitis A. Although the safety of inactivated vaccines is well established, further studies are needed concerning the implications of fecal virus shedding by recipients of attenuated vaccines, as well as the long-term persistence of immune memory in children receiving novel immunization schedules consisting of single doses of inactivated vaccines.

Seroprevalence and susceptibility to hepatitis A in the European Union and European Economic Area: a systematic review

Most of the European Union (EU) and European Economic Area (EEA) is considered a region of very low hepatitis A virus (HAV) endemicity; however, geographical differences exist. We did a systematic review with the aim of describing seroprevalence and susceptibility in the general population or special groups in the EU and EEA. We searched databases and public health national institutes websites for HAV seroprevalence records published between Jan 1, 1975, and June 30, 2014, with no language restrictions. An updated search was done on Aug 10, 2016. We defined seroprevalence profiles (very low, low, and intermediate) as the proportion of the population with age-specific anti-HAV antibodies at age 15 and 30 years, and susceptibility profiles (low, moderate, high, and very high) as the proportion of susceptible individuals at age 30 and 50 years. We included 228 studies from 28 of 31 EU and EEA countries. For the period 2000-14, 24 countries had a very low seroprevalence profile, compared with five in 1975-89. The susceptibility among adults ranged between low and very high and had a geographical gradient, with three countries in the low susceptibility category. Since 1975, EU and EEA countries have shown decreasing seropositivity; however, considerable regional variability exists. The main limitations of this study are that the studies retrieved for analysis might not be representative of all EU and EEA publications about HAV and might have poor national representativeness. A large proportion of EU and EEA residents are now susceptible to HAV infection. Our Review supports the need to reconsider specific prevention and control measures, to further decrease HAV circulation while providing protection against the infection in the EU and EEA, and could be used to inform susceptible travellers visiting EU and EEA countries with different HAV endemicity levels.

Time trends in pediatric hospitalizations for hepatitis A in Greece (1999-2013): Assessment of the impact of universal infant immunization in 2008

Hepatitis A vaccine was introduced in the Greek National Immunization Program in 2008. To estimate possible impact of the universal vaccination implementation, time trends of hospitalizations for hepatitis A at the Infectious Diseases Unit of a Tertiary Pediatric Hospital in Athens during 1999-2013 were analyzed. Hepatitis A hospitalizations were recorded from the discharge database and were expressed as frequencies and rate of annual departmental hospitalizations. Time series analysis (ARIMA) was used to explore trends and the impact of the vaccination. Moreover, changes in patient age, population group distribution and the duration of hospitalization were also examined. Hepatitis A hospitalizations rate significantly decreased between pre-vaccination (1999-2008) and post-vaccination (2009-2013) era from 50.5 to 20.8/1000 hospitalizations (p = 0.005). A 3-year periodicity and a trend of reduction on hepatitis A hospitalizations rates across years were noted. Roma children had significant higher rates of hepatitis A hospitalization, followed by immigrant children. Importantly, possibly due to preceding vaccine availability with considerable uptake in private market and unvaccinated group/pockets of children (Roma), overall vaccination effect was less apparent when compared to data from other countries that implemented universal vaccination. No significant change in patient age, population group distribution, or duration of hospitalization was observed. High risk groups such as Roma children should be targeted for vaccination to reduce future outbreaks.

Hepatitis Vaccines

Viral hepatitis is a serious health problem all over the world. However, the reduction of the morbidity and mortality due to vaccinations against hepatitis A and hepatitis B has been a major component in the overall reduction in vaccine preventable diseases. We will discuss the epidemiology, vaccine development, and post-vaccination effects of the hepatitis A and B virus. In addition, we discuss attempts to provide hepatitis D vaccine for the 350 million individuals infected with hepatitis B globally. Given the lack of a hepatitis C vaccine, the many challenges facing the production of a hepatitis C vaccine will be shown, along with current and former vaccination trials. As there is no current FDA-approved hepatitis E vaccine, we will present vaccination data that is available in the rest of the world. Finally, we will discuss the existing challenges and questions facing future endeavors for each of the hepatitis viruses, with efforts continuing to focus on dramatically reducing the morbidity and mortality associated with these serious infections of the liver.

Dissecting the indirect effects caused by vaccines into the basic elements

Vaccination directly protects vaccinated individuals, but it also has the potential for indirectly protecting the unvaccinated in a population (herd protection). Unintended negative consequences such as the re-manifestation of infection, mainly expressed as age shifts, result from vaccination programs as well. We discuss the necessary conditions for achieving optimal herd protection (i.e., high quality vaccine-induced immunity, substantial effect on the force of infection, and appropriate vaccine coverage and distribution), as well as the conditions under which age shifts are likely to occur. We show examples to illustrate these effects. Substantial ambiguity in observing and quantifying these indirect vaccine effects makes accurate evaluation troublesome even though the nature of these outcomes may be critical for accurate assessment of the economic value when decision makers are evaluating a novel vaccine for introduction into a particular region or population group. More investigation is needed to identify and develop successful assessment methodologies for precisely analyzing these outcomes.

Considerations on the current universal vaccination policy against hepatitis A in Greece after recent outbreaks

Greece is the only European Union member state that in 2008 included hepatitis A (HAV) vaccine in the routine national childhood immunization program (NCIP). Given that the resources allocated to public health have dramatically decreased since 2008 and that Greece is a low endemicity country for the disease, the benefit from universal vaccination has been questioned. The aim of this paper is to summarize the available epidemiological data of the disease for 1982-2013, and discuss the effects of universal vaccination on disease morbidity. Descriptive analysis, ARIMA modeling and time series intervention analysis were conducted using surveillance data of acute HAV. A decreasing trend of HAV notification rate over the years was identified (p<0.001). However, universal vaccination (~ 80% vaccine coverage of children) had no significant effect on the annual number of reported cases (p = 0.261) and has resulted to a progressive increase of the average age of infection in the general population. The mean age of cases before the inclusion of the vaccine to NCIP (24.1 years, SD = 1.5) was significantly lower than the mean age of cases after 2008 (31.7 years, SD = 2.1) (p<0.001). In the last decade, one third of all reported cases were Roma (a population accounting for 1.5% of the country’s total population) and in 2013 three outbreaks with 16, 9 and 25 Roma cases respectively, were recorded, indicating the decreased effectiveness of the current immunization strategy in this group. Data suggest that universal vaccination may need to be re-considered. Probably a more cost effective approach would be to implement a program that will include: a) vaccination of high risk groups, b) universal vaccination of Roma children and improving conditions at Roma camps, c) education of the population and travel advice, and d) enhancement of the control measures to increase safety of shellfish and other foods.

Effectiveness of 10-year vaccination (2001-2010) on Hepatitis A in Tianjin, China

Vaccination is an effective strategy to prevent and control the transmission of hepatitis A. Hepatitis A immunization program has been taken into effect since 2001 in Tianjin, China. This study evaluated the effectiveness of strategies in the prevention and control of hepatitis A. Data of serological survey, annual hepatitis A incidence, immunization coverage and the positive rate of hepatitis A IgG before and after the immunization program in residents under 15 years old were used to do the analysis. The results indicated that hepatitis A vaccine induced a striking decrease of hepatitis A incidence and a significant increase in the positive rate of anti-HAV IgG among the children younger than 15 years old. Hepatitis A vaccination in children was proved to be effective in the prevention and control of hepatitis A in Tianjin, China.

The impact of immigration and vaccination in reducing the incidence of hepatitis B in Catalonia (Spain)

BACKGROUND

The Hepatitis B virus (HBV) infection is a major cause of liver disease and liver cancer worldwide according to the World Health Organization. Following acute HBV infection, 1-5% of infected healthy adults and up to 90% of infected infants become chronic carriers and have an increased risk of cirrhosis and primary hepatocellular carcinoma. The aim of this study was to investigate the relationship between the reduction in acute hepatitis B incidence and the universal vaccination programme in preadolescents in Catalonia (Spain), taking population changes into account, and to construct a model to forecast the future incidence of cases that permits the best preventive strategy to be adopted.

METHODS

Reported acute hepatitis B incidence in Catalonia according to age, gender, vaccination coverage, percentage of immigrants and the year of report of cases was analysed. A statistical analysis was made using three models: generalized linear models (GLM) with Poisson or negative binomial distribution and a generalized additive model (GAM).

RESULTS

The higher the vaccination coverage, the lower the reported incidence of hepatitis B (p <0.01). In groups with vaccination coverage > 70%, the reduction in incidence was 2-fold higher than in groups with a coverage <70% (p <0.01). The increase in incidence was significantly-higher in groups with a high percentage of immigrants and more than 15% (p <0.01) in immigrant males of working age (19-49 years).

CONCLUSIONS

The results of the adjusted models in this study confirm that the global incidence of hepatitis B has declined in Catalonia after the introduction of the universal preadolescent vaccination programme, but the incidence increased in male immigrants of working age. Given the potential severity of hepatitis B for the health of individuals and for the community, universal vaccination programmes should continue and programmes in risk groups, especially immigrants, should be strengthened.

Era of vaccination heralds a decline in incidence of hepatitis A in high-risk groups in China

BACKGROUND

Hepatitis A was ranked first among all of the different types of viral hepatitis in China, which occurred an average of 500,000 cases annually during the 1980's. A live attenuated hepatitis A vaccine was applied in preventing of the disease in 1992, large scale used in vaccination program in 1995, and incorporated in the Expanded Program of Immunization in 2008 in China.

OBJECTIVE

The objective of this study was to determine whether, and to what extent, the decline in the incidence of hepatitis A in China was the result of hepatitis A (HA) vaccination.

MATERIALS AND METHODS

Official documents and longitudinal serological follow-up studies were reviewed to compare the incidence of HA before and after the introduction of the vaccine.

RESULTS

National trends in the incidence of HA in China saw rates decrease by 92.7% in 2009, compared to the levels seen in 1992. A mass vaccination program was carried out in 3-18 year old children (Wuhan City, China), and its protective efficacy was 85.4%. In a mass vaccination program of an entire population (Shenshi County, China), the annual HA incidence decreased from 359.7/100,000 to 17.7/100,000 (almost 20.3 times). There was a significant relationship found between vaccine coverage and the incidence of HA, the correlation of the negative regression was significant at the 1% (Kendall rank correlation, significant level P < 0.05).

CONCLUSIONS

In summary, this study highlights the important role of implementing a vaccination program in decreasing the incidence of HA, and the large protective efficacy of such a strategy, as demonstrated in China.

Decline in HAV-associated fulminant hepatic failure and liver transplant in children in Argentina after the introduction of a universal hepatitis A vaccination program

INTRODUCTION

Hepatitis A virus (HAV) infection is a vaccine-preventable disease. The most severe complication in children is fulminant hepatic failure (FHF), estimated to occur in 0.4% of cases; patients with FHF often require a liver transplant (LT). Following another outbreak of HAV infection in Argentina during 2003-2004, a one-dose HAV universal immunization (UI) program was started in 2005, resulting in a reduction in the incidence of HAV infection. We have investigated the impact of HAV UI on the trends in the occurrence of FHF and LT in children.

METHODS

All pediatric cases of FHF admitted to four pediatric centers in Buenos Aires during March 1993-July 2005 were retrospectively reviewed, and data of cases during August 2005-December 2008 were collected. Information about demography, HAV infections and vaccination status, diagnostic data for FHF using the Pediatric Acute Liver Failure criteria, clinical laboratory results, encephalopathy, the severity of liver disease using the Pediatric End Stage Liver Disease score, assessment of patients on the LT waiting list using King's College Criteria for LT, treatment given for FHF (pre- and post-transplant), and clinical outcome were collected using a case report form. The frequency and outcomes of HAV-associated FHF and LT cases before and after UI were analyzed.

RESULTS

During the pre-immunization period, March 1993-July 2005, 54.6% (N = 165) of FHF cases were caused by HAV; HAV-associated FHF cases peaked during 2003-2004. During the post-immunization period, August 2005-December 2008, only 27.7% (N = 18) of FHF cases were caused by HAV infection; only one of these patients had received the HAV vaccine (one dose only). The number of HAV-associated FHF cases decreased from 2005, and no cases were reported from November 2006-December 2008. Multivariate analyses showed that the association of FHF with HAV infection rather than other etiologies decreased with increasing age (P = 0.03), UI against HAV (P = 0.002), and anti-actin antibodies (P = 0.002), and increased with increasing weight (P = 0.0004).

CONCLUSIONS

The number of children with HAV-associated FHF in Argentina has strongly decreased since the initiation of the UI program. Further monitoring is required to confirm the long-term health and economic benefits of UI against HAV infection.

Strategy for hepatitis A seroprevalence survey in a population of young people

In the present research a novel operative strategy of health surveillance with a reduced number of serologic tests is proposed. The approach consists to identify sub-populations with high predictable serological profile that makes the serological tests unnecessary. The study is focused on assays done to detect the response against hepatitis A, which in Italy displays low/intermediate endemicity. Receiver operating characteristics analysis performed on data from documented and self-reported vaccination information of a cohort of students from Padua University Medical School confirmed that anti-hepatitis A antibodies measurement might be avoided in subjects younger than 30 years with negative documented or self-reported history of vaccination or subjected to current vaccination schedule.

Incidence of Hepatitis A in Argentina after vaccination

In Argentina, the annual incidence rate of reported hepatitis A disease ranged from 70.5 to 173.8 per 100,000 during 1995-2004. A single dose universal hepatitis A immunization program aimed at children aged 12 months was started in June 2005. The aim was to observe the impact of universal vaccination against hepatitis A in Argentina. A longitudinal analysis of hepatitis A rates reported in Argentina since 1995 to the National Notifiable Diseases Surveillance System (SINAVE). Incidence rates in 2007 were compared with those for the prevaccination baseline period (1998-2002), overall and by age group and geographical regions. Overall vaccine coverage in Argentina was 95% in 2006 for the single dose. After initiating the program, a sharp decrease in disease rates was observed. The annual incidence of 10.2 per 100,000 during 2007 represents 88.0% reduction with respect to the average incidence rate for the period 1998-2002 (P < 0.001). For children aged 1 year, an 83.1% reduction in disease was observed in 2007, compared with the baseline period (P < 0.001). Furthermore, a sharp decline was also observed in all other age groups 87.1% [2-4 years], 88.7% [5-9 years], 83.6% [10-14 years], 78.8% [15-49 years], 20.7% [>50 years]. Also important reductions were observed in all Argentinian regions. Following the implementation of universal hepatitis vaccination with a single dose to children at 12 months of age, hepatitis A rates have declined substantially in Argentina. Monitoring is needed to verify that vaccination continues to proceed and that low rates are sustained.

Long-term trends in hepatitis A incidence following the inclusion of Hepatitis A vaccine in the routine nationwide immunization program

For many years hepatitis A was one of the most common vaccine preventable diseases in Israel. In 1999, Israel became the first country to introduce an inactivated hepatitis A vaccine into its national childhood vaccination program. The objectives of the present study were to study trends in disease incidence after the implementation of the new vaccination policy and to assess vaccination coverage among children and adults in Israel. We used the databases of the second largest HMO in Israel (1.7 million members) to identify patients who had evidence of hepatitis A in 1998 and 2007 and to collect information on all subjects who received at least one dose of hepatitis A vaccine during the study period. Hepatitis A vaccination coverage in children <5 years and 5-14 years of age increased from 9% and 15% in 1998 to 89% and 68% in 2007, respectively. During this period the annual incidence of hepatitis A dropped from 142.4 per to 7.6 per 100 000. The most prominent reduction in the age-specific annual incidence rates was calculated in children <5 years from 239.4 per 100 000 in 1998 to 2.2 per 100 000 in 2007 and from 310.3 per 100 000 to 3.0 per 100 000 in children aged 5-14 years. In endemic areas, vaccination of infants and children against hepatitis A can greatly reduce the total burden of the disease.

Prevalence of hepatitis B virus markers among blood donors in a tertiary hospital in Tabuk, northwestern Saudi Arabia

OBJECTIVE

This study was carried out to determine the prevalence of hepatitis B virus (HBV) markers among blood donors in a tertiary hospital in Tabuk, northwestern Saudi Arabia.

MATERIALS AND METHODS

A cross-sectional survey was done among male Saudi voluntary blood donors at the blood bank of the King Khalid tertiary care hospital in the northwest region of Saudi Arabia. A total of 3192 subjects were included in the study over the period from June 1, 2005 to May 31, 2006. Subjects were tested for evidence of HBV infection plus other relevant blood-borne pathogens. A questionnaire sheet for the collection of personal information (such as name, age, and sex), socioeconomic data (such as marital status, education, and occupation), family history of HBV infection, history of immunization against HBV, and history of past exposure to a high risk procedure or behavior, was prepared and used for each subject. Data were tabulated and statistically analyzed.

RESULTS

Among the studied sample, the prevalence of HBsAg (hepatitis B surface antigen) was found to be 3.0% and the prevalence of anti-HBc (anti-hepatitis B core antigen) was found to be 18.7%. Blood donors with positive HBV markers showed significant association with increased age, being married, lower educational level, specific occupations such as blue collar worker and the military, family history of HBV infection, and lack of immunization. However, there was no significant association with history of exposure to high-risk procedure or behavior.

CONCLUSIONS

The prevalence of HBV infection among male Saudi blood donors in the northwest region of Saudi Arabia is high compared to that reported from the central capital area (Riyadh). Public health education programs on HBV infection, adult hepatitis B immunization programs, and raising socioeconomic standards should be initiated in order to target the high-risk groups found in this study. Furthermore, a community-based study is recommended to investigate HBV infection in the northwest region of Saudi Arabia.

Long-term antibody persistence induced by a combined hepatitis A and B vaccine in children and adolescents

Two cohorts, comprising of subjects aged 1-6 years and 6-15 years were vaccinated with Twinrix according to a 0-, 1- and 6-month schedule. The 1-6 years cohort was followed up for 7.5 years and the 6-15 years cohort for 10 years. At the latest follow-up time point, all subjects were seropositive for anti-HAV antibodies, while 86.5% (32/37) and 95.5% (21/22) had anti-HBs >or= 10 mIU/ml in the 1-6 years and in the 6-15 years cohort. The geometric mean concentrations (GMCs; mIU/ml) were 233 and 680 for anti-HAV antibodies, and 147 and 165 for anti-HBs antibodies, in the 1-6 years and 6-15 years cohorts, respectively. The high persistence of circulating anti-HAV and anti-HBs antibodies in children and adolescents demonstrates the long-term protection offered by Twinrix in these age groups.

The shifting epidemiology of hepatitis A following routine childhood immunization program in Israel

OBJECTIVES

In 1999 Israel became the first country to introduce immunization against hepatitis A to its national childhood vaccination program. The study objectives were to assess the uptake of hepatitis A vaccine following the new policy and to examine the incidence of hepatitis A and the number of prevented cases.

METHODS

Data on incidence of hepatitis A and vaccination rates were obtained from a large health maintenance organization in Israel covering 1.6 million members. We identified all members that were diagnosed by a primary care physician as suffering from hepatitis A, had a positive hepatitis A virus-IgM test result, or were hospitalized due to hepatitis A between 1998 and 2004.

RESULTS

The results indicate that 5 years following its inclusion in the national childhood immunization program, vaccination coverage levels with at least one dose of hepatitis A vaccine for children aged under 5 years and 5-14 years were 87% and 51%, respectively. During this period the annual incidence rates declined by 88% from 142.4 to 17.3 per 100,000. The most significant reduction in morbidity was observed among children.

CONCLUSIONS

In endemic areas, vaccination of infants and children against hepatitis A may be efficient to greatly reduce the total burden of the disease.

Epidemiological and virological characterization of a large community-wide outbreak of hepatitis A in southern Italy

A large outbreak of hepatitis A virus (HAV) infection occurred in 2004 in Campania, a region of southern Italy, with 882 cases reported between 1 January and 1 August. The local public health authorities and the Italian National Institute of Health carried out investigations in order to characterize the agent, identify the source of infection and the route of transmission, and implement appropriate control measures. A web-based reporting system enhanced the flow of information between public health authorities, providing real-time epidemic curves and frequency distributions. The same 1B HAV genotype was found in 90% of sera from a subset of patients with acute disease, suggesting a local common source. A case-control study in the municipality with the highest attack rate showed that raw seafood consumption, in particular if illegally sold in water, was strongly associated with HAV illness. Samples of seafood systematically collected from retailers were found contaminated by HAV.

Immunogenicity and safety of a pediatric dose of a virosome-adjuvanted hepatitis A vaccine: a controlled trial in children aged 1-16 years

BACKGROUND

The availability of pediatric formulations of hepatitis A virus (HAV) vaccines would facilitate the introduction of universal mass vaccination against HAV. The objective of this study was to compare a pediatric dose (0.25 mL) of Epaxal, a virosomal, aluminum-free HAV vaccine, to 0.5 mL standard dose, and to alum-adsorbed HAV vaccine.

METHODS

Subjects aged 1-16 years, stratified for age, were randomized (2:2:1) into group A (0.25 mL Epaxal), group B (0.5 mL Epaxal), or group C (Havrix Junior). Vaccines were administered at months 0, 6. Seroprotection rates (>or=10 mIU/mL anti-HAV antibodies) were assessed for noninferiority, defined as lower limit of 1-sided 97.5% CI >-10%. Incidence of local solicited adverse events and unsolicited adverse events were recorded.

RESULTS

Mean age of 308 enrolled subjects was 8.9 years (range, 1.0-17.0 years). All 3 vaccines were highly immunogenic. Noninferiority of group A versus group B and group C with regard to seroprotection was demonstrated after both vaccine doses for the entire study group and for all age subgroups (11-23 months, 2-4, 5-7, 8-10, 11-13, 14-16 years). One month after first vaccination, geometric mean antibody concentrations were 69.0, 83.5, and 50.5 mIU/mL for the 3 groups, respectively (A versus B, P = 0.0208; A versus C, P = 0.0015). Local injection site pain occurred more frequently in group C than in groups A and B. No subjects withdrew from study or reported any vaccine-related serious adverse event.

CONCLUSION

In children aged 1-16 years, 0.25 mL dose of Epaxal is as immunogenic as standard 0.5 mL dose and Havrix Junior. The aluminum-free vaccine compares favorably to comparator vaccine regarding local reactogenicity.

Epidemiology of travel-associated and autochthonous hepatitis A in Austrian children, 1998 to 2005

BACKGROUND

In Austria, being an area of low hepatitis A endemicity, every year, several cases of this infectious disease are reported. The aim of the present study was to provide data on disease and hospitalization of children below the age of 15 for imported and autochthonous hepatitis A in Austria.

METHODS

Nationwide, active, hospital-based surveillance during the period 1998 to 2005.

RESULTS

During this 8-year observation period, 413 children below 15 years of age were hospitalized with acute hepatitis due to infection with hepatitis A . The mean annual incidence of hospitalization per 100,000 population was 3.8, with a decreasing trend from 1998 to 2005. The mean length of hospital stay attributable to hepatitis A was 6.5 days. The mean annual number of days of hospitalization attributable to acute hepatitis A infection in children below 15 years of age was 335 days. Information on origin of infection was available in 48% of the reports, the majority of which (69%) were in consequence of infection import. The mean annual incidence of travel-associated, hospitalized hepatitis A cases was 1.3 per 100,000, showing a lesser decrease rate over the observation period than the total hospitalization incidence.

CONCLUSIONS

In an area of low hepatitis A endemicity such as Austria, hospitalization incidence of children is still at a considerable level. Our findings contribute to an open discussion about universal childhood vaccination.

Hepatitis A vaccine recommendations

Since licensure in 1995 of a hepatitis A vaccine, the Centers for Disease Control and Prevention and the American Academy of Pediatrics have been implementing an incremental hepatitis A immunization strategy for children. In 1996, children living in populations with the highest rates of disease were targeted for immunization, and in 1999 the program was expanded to immunization of children 2 years and older living in states and counties with rates of hepatitis A that historically have been higher than the national average. The 1999 program has been successful; the current rate of hepatitis A is the lowest ever reported in the United States. Regional, ethnic, and racial differences in the incidence of hepatitis A have been eliminated. The incidence of hepatitis A in adults in immunizing states has decreased significantly, suggesting a strong herd-immunity effect associated with immunization. In 2005, the US Food and Drug Administration changed the youngest approved age of administration of hepatitis A vaccine from 24 to 12 months of age, which facilitated incorporation of the vaccine into the recommended childhood immunization schedule. As the next step in the implementation of the incremental vaccine immunization strategy, the American Academy of Pediatrics now recommends routine administration of a Food and Drug Administration-licensed hepatitis A vaccine to all children 12 to 23 months of age in all states according to a Centers for Disease Control and Prevention-approved immunization schedule. Available data suggest that hepatitis A vaccine can be coadministered with other childhood vaccines without decreasing immunogenicity. Hepatitis A vaccines have proven to be extremely safe. In prelicensure clinical trials of both Havrix (GlaxoSmithKline, Rixensart, Belgium) and Vaqta (Merck & Co Inc, Whitehouse Station, NJ), adverse events were uncommon and mild when they occurred, with resolution typically in less than 1 day. Hepatitis A vaccine is contraindicated in people with a history of severe allergic reaction to a previous dose of hepatitis A vaccine or to a vaccine component. Because the hepatitis A vaccine is an inactivated product, no special precautions are needed for administration to people who are immunocompromised. No data exist about administration of the hepatitis A vaccine to pregnant women, but because it is not a live vaccine, the risk to mother and fetus should be extremely low to nonexistent.

Marked decrease in the incidence and prevalence of hepatitis A in the Basque Country, Spain, 1986-2004

The aim of this study was to determine changes in the epidemiology of hepatitis A virus (HAV) infection in the Basque Country, Spain, and to evaluate their implications for vaccination strategies. A total of 1356 persons were enrolled in a study of the prevalence of anti-HAV in 2004 and compared with two previous studies (1986-1987 and 1992). The selection method and the characteristics of the population were similar in the three studies. A marked decline in the seroprevalence in all age groups (P<0.001) and in the incidence of cases/100,000 inhabitants (from 38.0 in 1986-1988 to 2.9 in 2002-2004) were observed. The mean age of patients with hepatitis A increased from 17.7 years in 1986-1992 to 21.2 years in 1993-1998 and 25.3 years in 1999-2004 (P<0.001). Between 1997 and 2004, 20% of patients were hospitalized. The changes observed have occurred rapidly causing a change in the epidemiological pattern from middle-high endemicity (1986) to low endemicity (2004).

[Community outbreak of hepatitis A in a marginal population. Vaccination for its control and acceptance of the measure]

OBJECTIVE

To study a community outbreak of hepatitis A in a marginal population and the public health response in order to bring it under control.

DESIGN

Descriptive study of the outbreak that occurred in February-June, 2004. An epidemiological survey was conducted to detect prior cases and active vigilance was set up. Case and susceptibility definitions were established.

SETTING

A gypsy population in Madrid, Spain. They had basic provision of sewerage, water supply and waste disposal.

PARTICIPANTS

A population of 550 in census; estimated population, 800. 70% were under 40 and 55% were illiterate.

INTERVENTIONS

Control measures were: a) health education activities to strengthen habits of hygiene, and b) immunisation of susceptible individuals. A total of 646 people were vaccinated, with the active help of staff from the Institute of Rehousing and Integration into Society.

RESULTS

The outbreak affected 26 people, with an average age of 8 (95% CI, 6.2-9.8), similar distribution by sex and 3.3% attack rate. Fourteen cases were students at state schools, not all in the same classes. There were 7 pairs of siblings among the cases. The diagnosis was conformed by serology in 17 cases. Five needed hospital admission.

CONCLUSIONS

The epidemic curve suggested person-person transmission. All those affected were under 20 years old. Vaccination was seen to be effective in controlling the outbreak. Interventions were assisted by intermediaries in order to respect the gypsies' cultural context and were well accepted.

The cost-effectiveness of universal vaccination of children against hepatitis A in Argentina: results of a dynamic health-economic analysis

BACKGROUND

Socioeconomic improvements can reduce levels of endemic hepatitis A, but conversely increase the burden of disease. Routine childhood vaccination can rapidly control hepatitis A infection rates through the induction of herd immunity, although such programs can be costly.

METHODS

We evaluated the healthcare benefits and cost-effectiveness of a routine childhood vaccination program against hepatitis A in Argentina, using a dynamic model that incorporated the changing epidemiology of infection and the impact of vaccine-induced herd immunity. Demographic, disease, and economic data from Argentina were used where available.

RESULTS

At 95% coverage, the program would reduce the number of hepatitis A infections by 352,405 annually, avoiding 121,587 symptomatic cases and 428 deaths. Substantial healthcare benefits were also observed with vaccination coverage as low as 70%, which would prevent 295,826 infections. Economically, the program would save 23,989,963 US$ annually at 95% coverage, equivalent to 3,429 US$ per life-year gained. The program remained cost-saving in response to variation in factors, including disease-related costs, discount rate, herd immunity level, and rate of decrease of force of infection. The break-even cost per vaccine dose for the society was 25 US$ in the base-case, more than three times the current public cost of 7 US$ per dose.

CONCLUSIONS

Routine childhood vaccination against hepatitis A showed both health benefits and robust economic benefits in this analysis, supporting the recent decision of the Argentine government to implement such a program.

Universal mass vaccination against hepatitis A

When first introduced in 1992 the hepatitis A vaccine was recommended for individuals at high risk of exposure. This policy was not expected to have a significant impact on disease incidence at population level in view of the epidemiology of the hepatitis A virus (HAV). More recently two countries, Israel and Bahrain, and regions or subpopulations in others (Australia, China, Byelorussia, Italy, Spain, US) have embarked upon more ambitious vaccination programmes that aim to immunize whole birth cohorts. After a brief survey of the virology and epidemiology of HAV, the disease burden it inflicts and a short history of the development of HAV vaccines--both live (in China) and killed vaccines are available--he vaccination programmes introduced in the countries mentioned above are described. The results have been spectacular: disease incidence, not only in the vaccinated cohorts but also in the whole population, have plummeted within a few years of the start of mass vaccination. There is now convincing evidence that the vaccine confers herd immunity if the main spreaders of the virus are targeted for immunization. This finding should encourage other countries to start mass vaccination programmes against HAV, particularly as pharmacoeconomic studies are beginning to show that such a strategy could be a cost-effective way of controlling the disease. It is now even conceivable to eradicate HAV. In fact, this should be easier to achieve than polio eradication as HAV vaccines confer more durable immunity than polio vaccines. However, the global disease burden of HAV is generally thought not to be high enough to justify such an undertaking in the foreseeable future.

Impact et modélisation des effets attendus de la stratégie de vaccination contre les hépatites A chez les militaires français, 1990-2004

BACKGROUND

Hepatitis A is a public health problem specially for migrants or travellers from industrialized countries with a low hepatitis A endemic level. French armed forces adopted an immunization strategy which first targeted overseas forces and subsequently was extended to all armed forces. In this work we studied the impact of this policy.

METHODS

Epidemiological surveillance data from 1990 to 2004 was analyzed by Poisson regression and exponential models of decrease used to forecast future rates.

RESULTS

From the 826 cases of hepatitis A reported during the study period, 266 (32.2%) occurred in overseas forces and 560 (67.8%) in forces stationed in France. Three periods could be identified in the decline of annual incidence: before 1994, with an average rate of 23.2 per 100,000; from 1994 to 1998: 10.2; and after 1998: 1.2 for all French armed forces. For overseas armed forces, the average rate was 117 per 100,000 before 1994 and 17.1 from 1994 to 1998 (p<0.001). For armed forces stationed in France, the average rate was 12.2 per 100,000 before 1998 and 0.9 after (p<0.001). For overseas armed forces, models clearly described the declining incidence subsequent to targeted immunization in 1995 and for armed forces stationed in France, the decline with generalized immunization starting in 1998.

DISCUSSION

The impact of immunization against hepatitis A virus was significant both in an overseas population and in a population staying in France where the risk level can be considered low due to the low endemic rate in France. These results suggest that immunization should be proposed not only for travellers but also for the general population based on real knowledge of the situation and cost-effectiveness analyses.

Prevention of hepatitis A by Havrix: a review

Hepatitis A is one of the most common vaccine-preventable infectious diseases in the world. With at least 1.5 million cases of hepatitis A worldwide each year, disease management constitutes a substantial economic burden. The first effective vaccine against hepatitis A, Havrix was introduced in 1992. This review summarizes data accumulated following more than a decade of clinical experience with this vaccine and compares clinical data with other currently available hepatitis A vaccines. Based on this data and on the current immunological knowledge, a recent consensus concluded that hepatitis A vaccines induce lifelong protection, and thus booster vaccinations against hepatitis A are unnecessary in fully immunized, healthy people. In view of this, current regulatory recommendations for the use of hepatitis A vaccines are reviewed and possible future strategies identified.

Changing prevalence, clinical features, and outcome of acute hepatitis in Spain (1982-2003)

BACKGROUND

Diagnostic and preventive measures have contributed to a change in the epidemiology of acute hepatitis. The purpose of the present paper was to assess the changing prevalence of acute hepatitis from 1982 to 2003.

METHODS

Trends in the epidemiology, clinical findings, and outcome of acute viral hepatitis from 1982 to 2003 were examined. A total of 548 episodes of acute hepatitis diagnosed between 1982 and 2003, the clinical course of which was monitored up to the year 2003, were included. Annual changes as well as for the intervals 1982-1992 and 1993-2003 were compared.

RESULTS

Severe infections occurred in 1.3% of cases, with a mortality of 0.6%, with progression into chronicity in 25.1%. The annual incidences of acute hepatitis and the comparative intervals 1982-1992 and 1993-2003 showed a decline of parenterally -B, delta and C virus- transmitted infections, unchanged number of cases of acute hepatitis A, an increase in the number of cases of drug-induced hepatitis, increase in median ages, and a decrease in the proportion of hepatitis in injecting drug users. Ages of patients with hepatitis A tended to increase.

CONCLUSIONS

A decline of parenterally transmitted acute hepatitis was documented throughout a 22-year period, while the number of cases of hepatitis A was unchanged and that of drug-induced hepatitis increased. Evaluation of the current targeted hepatitis A vaccination approach and adequate pharmacovigilance measures are required in the near future.

Anti-hepatitis A virus frequency in adolescents at an outpatient clinic in São Paulo, Brazil

The prevalence of hepatitis A virus (HAV) antibodies was assessed in adolescents (age ranging from 10.4 to 19.9 years) at an Adolescent Outpatient Clinic in São Paulo, Brazil. Anti-HAV was detected in 137 (54.2%) out of 253 individuals. When separated into two age groups, anti-HAV frequency was higher in the 15 to 19 year-old group (64%) in comparison to the 10 to 14 year-old group (46%) (Chi-square test: p = 0.004). These results suggest that adolescents in São Paulo are at risk of hepatitis A infection and are probably contracting HAV infection during this age period.

Determinants of acquiring hepatitis A virus disease in a large Italian region in endemic and epidemic periods

Viral hepatitis A is endemic in Puglia region (southeast Italy). Over the last 13 years, annual incidence rates have ranged from 4 to 138 per 100,000 inhabitants and periodical regional epidemics have been described. Between 1 January 1996 and 31 December 1997 over 11,000 cases of hepatitis A were reported accounting for an annual incidence rate over 130/100,000. To identify exposures during the epidemics, a case-control study was performed in two different rounds and since 1997, an enhanced surveillance system has permitted the monitoring of exposures of subsequent cases. Raw seafood consumption was identified as the major risk factor for hepatitis A. Adjusted odds ratio and 95% confidence intervals for this exposure from the first round of the case-control study was 38.6 (12.2-122.4) and for the second round for consumption of raw mussels it was 30.7 (16.0-52.0). Hepatitis A epidemiology in Puglia is consistent with an endemic situation sustained by locally contaminated seafood consumed raw and by the recurrence of large epidemics, where size is influenced by the accumulation of susceptible subjects in the population.

Reactogenicity profile of a combined hepatitis A and B vaccine in clinical practice: a naturalistic study in adult travellers

A prospective observational naturalistic study was conducted to assess the reactogenicity of the combined hepatitis A and hepatitis B (HAB) vaccine in a real-life setting. All healthy candidates for HAB vaccination attending an adult vaccination centre between October 1998 and February 2000 were invited to participate in the study. A follow-up diary card was provided to subjects to record local and general symptoms during a 4-day follow-up. Intensity was graded from 1 to 3. Redness was recorded as presence or absence. Fever was defined as axillar temperature > or =37.5 degrees C and grade 3 >39.0 degrees C. For all other symptoms, grade 3 was defined as an adverse reaction preventing normal everyday activities; 998 subjects (74% females), mean age (+/-S.D.) of 23 years (+/-4.5) (range: 11-54 years) agreed to participate. At first immunization 92% were <30 years old. Grade 3 pain and swelling was recorded in 1.2% and 0.3% of local symptom sheets completed, respectively; 438 subjects received the HAB vaccine alone (group 1) whereas 560 received at least one concomitant vaccine (group 2). In 45%, 27%, 18% and 10% of subjects the HAB vaccine was coadministered with 1, 2, 3 or 4 to 6 vaccines (mainly Td adult-type, typhoid, MMR and IPV vaccine). Grade 3 pain and swelling were recorded in 1.2% & 0.3% of symptom sheets (SS), respectively. In group 1, any fever and grade 3 fever was recorded in 3.5% and 0.1% of SS. Group 1 versus 2 had a lower risk for any fatigue (p=0.0002; OR=0.617) and any malaise (p=0.0076; OR=0.693) but not for grade 3 symptoms. In conclusion, our study showed that the HAB vaccine is well tolerated in adults either alone or coadministered with other vaccines in the routine clinical practice.

Combined hepatitis A and B vaccines: a review of their immunogenicity and tolerability

Three combined hepatitis A and B vaccine preparations are commercially available in various countries: a two-dose paediatric formulation (Ambirix) [administered at months 0 and 6-12]; and a three-dose adult (Twinrix Adult) or paediatric (Twinrix Paediatric) formulation (administered at months 0, 1 and 6). The adult vaccine provides consistent, marked immunogenicity which is at least similar to that of its constituent vaccines used together and with a tolerability profile that is possibly improved. An accelerated, day-0, -7 and -21 regimen has also shown immunogenicity similar to that of the monovalent vaccines given concurrently, and now has an emerging role in adults likely to travel to hepatitis A virus (HAV) and/or hepatitis B virus (HBV) endemic regions within 1 month. The adult vaccine appears effective and generally well tolerated when given concurrently with monovalent typhoid vaccine (Typherix). Immunogenicity of the two-dose paediatric vaccine is high and appears to be similar whether administered as a month-0, -6 or month-0, -12 schedule and when compared to that of the three-dose paediatric vaccine (months 0, 1, 6), both of which provide a similar degree of protection to the adult vaccine. Although both preparations also provide high end-of-schedule seroprotection against hepatitis B surface antigen, protection between the first and second doses of the two-dose regimen appears lower than with the three-dose schedule. Therefore, the three-dose paediatric vaccine is a practical option in individuals at risk of immediate exposure to HBV, while the two-dose regimen may have an important function in immunisation programmes in regions where such risk is low. Combined hepatitis A and B vaccines are generally well tolerated. The most frequently reported adverse events in clinical trials were injection-site pain and redness, and general fatigue and headache; most events were mild and transient. Pharmacoeconomic models suggest the combined vaccine is cost effective compared with no vaccine (in children/adolescents) or monovalent hepatitis B vaccine (in children/adolescents and prison inmates).

CONCLUSION

The three commercially available combined hepatitis A and B adult and paediatric vaccines are highly immunogenic and generally well tolerated; the adult vaccine demonstrates immunogenicity at least as marked as that of monovalent hepatitis A and B vaccines. While further research is required to confirm potential advantages such as improved cost effectiveness, the combined vaccines have established a key role in the prevention of hepatitis A and B in defined risk groups, and have an expanding role in population-based vaccination programmes with younger age groups.

Calendario vacunal de la Asociación Española de Pediatría: recomendaciones 2004

The Vaccine Assessment Committee of the Spanish Association of Pediatrics discusses vaccine developments in 2003 and recommends some modifications to the vaccination schedule. The recommendation of substituting the oral polio vaccine for the inactivated polio vaccine, suppressing the fifth dose, is maintained. The introduction of the conjugate pneumococcal vaccine and the varicella vaccine is stressed. Concerning the meningococcal C vaccine, the improvement introduced by being able to immunize with just two doses is discussed. In agreement with the information received from the European Medicines Agency, there appear to be no well-founded reasons to abandon hexavalent preparations.

Hepatitis A booster vaccination: is there a need?

Hepatitis A is one of the most common vaccine-preventable infectious diseases in the world. Effective vaccines against hepatitis A have been available since 1992, and they provide long-term immunity against the infection. However, there is no worldwide consensus on how long protection will last or whether there will be a need for hepatitis A virus (HAV) booster vaccinations in the future. In most countries, booster-vaccination policy is guided by manufacturers' recommendations, national authorities, or both. In June, 2002, a panel of international experts met to review the long-term immunogenicity and protection conferred by HAV vaccine in different population groups. Data have shown that after a full primary vaccination course, protective antibody amounts persist beyond 10 years in healthy individuals, and underlying immune memory provides protection far beyond the duration of anti-HAV antibodies. The group concluded that there is no evidence to lend support to HAV booster vaccination after a full primary vaccination course in a healthy individual. However, further investigations are needed before deciding if boosters can be omitted in special patient-groups.

Genetic analysis of HAV strains recovered from patients with acute hepatitis from Southern Italy

Southern Italy is an endemic area for HAV infection contributing to the majority of Italian hepatitis A cases. Using molecular analysis, HAV strains have been classified in distinct genotypes and subgenotypes. To characterize HAV wild-type strains circulating in Southern Italy, sequence analysis of VP3-VP1 and VP1/2A junction regions of HAV isolates recovered from 25 patients with acute hepatitis during 2000 and 2001 was carried out. HAV isolates showed a degree of identity, after pairwise comparison with one another, ranging from 91.9-100% in the VP3-VP1 junction region and 89.9-100% in the VP1/2A junction region. All strains belonged to genotype I, with 84% (21/25) of samples clustering in subgenotype IA and 16% (4/25) in subgenotype IB. Cocirculation of subgenotypes IA and IB was observed among isolates from 2000, whereas all strains from 2001 were subgenotype IA. In addition, the subgenotype IA strains formed different clusters, one of which was related closely to some Cuban strains, showing a percent similarity of 98.8% in the 168-base pair segment encompassing the VP1/2A junction and the same amino acid substitution. The latter finding suggests that this subgenotype variant circulates also in the Mediterranean area. The results of the phylogenetic analysis confirm the genetic heterogeneity among HAV strains in Western Europe.

Inactivated hepatitis A vaccine: immunogenicity, efficacy, safety and review of official recommendations for use

There is 10 years of marketing experience with the hepatitis A vaccine Havrix. It is highly immunogenic, provides lasting protection in healthy individuals and generates protective levels of antibodies in patients with chronic liver disease or impaired immunity. Postmarketing surveillance data have confirmed the outstanding safety profile of the vaccine. The timing of the booster dose is not critical to effectiveness, which has advantages for the protection of travelers to regions of high endemicity. The vaccine is effective in curbing outbreaks of hepatitis A and also when administered postexposure, due to rapid seroconversion and the long incubation period of the disease. In intermediate endemic regions, an epidemiological shift in hepatitis A infection has driven the development of universal preventive strategies to be added to the targeting of at-risk groups. Existing official recommendations and future directions for vaccine use are reviewed.

Genetic analysis of hepatitis A virus strains recovered from the environment and from patients with acute hepatitis

The molecular epidemiology of hepatitis A virus (HAV) was studied by analysing HAV strains recovered from environmental water samples over a 7 year period and strains recovered from patients with acute hepatitis over a 5 year period. A total of 54 samples of raw domestic sewage and 66 samples of river water were collected. HAV particles were concentrated and detected by nested RT-PCR. HAV infection in patients with acute hepatitis was serologically diagnosed in 26 of 74 serum samples, which were also analysed by nested RT-PCR. HAV RNA was detected in 57.4% of sewage samples, 39.2% of Llobregat river water samples, 20% of Ter river water samples and 61.6% of serum samples. The HAV genomes detected were characterized further by directly sequencing a region of the 5' non-translated region, the VP1/2A junction region and, in some samples, the 2B region. Results showed a 95% prevalence of genotype I, with nearly 50% being either subgenotype IA or subgenotype IB. Various strains were found simultaneously in both environmental and clinical samples. These strains were closely related to those described in distant geographical areas. Genotype IIIA was also found in 5% of sewage samples and in 12.5% of serum samples. Strains belonging to a common endemic genotype were not identified. The abundance of HAV in the environment produces a situation of sanitary risk, especially considering the low prevalence of antibodies in the young population.

Vaccination against hepatitis A in children aged 12 to 24 months [corrected]

BACKGROUND

Current hepatitis A vaccines are either licensed for children >2 years of age, as in the U.S. or Chile, or >1 year of age, as in Europe and other parts of the world. Recent recommendations for immunization against hepatitis A have included routine vaccination of children in areas or regions of higher endemicity. However, data on hepatitis A vaccination in toddlers aged between 1 and 2 years are scarce.

METHODS

This open clinical study investigated the reactogenicity and immunogenicity of two doses (0, 6-month schedule) of an inactivated hepatitis A vaccine (Havrix pediatric, Glaxco SmithKline Biologicals, Rixensart, Belgium) in 120 seronegative children aged 12-24 months.

RESULTS

Pain at the injection site and irritability were the most frequently reported local and general symptoms, respectively. No serious adverse events related to the study vaccine were reported. One month after the first dose, all but one subject had antibodies against hepatitis A with a GMT of 159 mIU/mL. After the booster dose, all had antibodies with a GMT of 2,939 mIU/mL.

CONCLUSIONS

Our data show that the inactivated hepatitis A vaccine was well tolerated by these toddlers and that the vaccine elicits a good immune response.

Combining hepatitis A and B vaccination in children and adolescents

Hepatitis A and B are common infections worldwide and their severity is related to the individual's age upon initial infection. Furthermore, when hepatitis B infection occurs in infants, the risk of becoming a chronic carrier is 90%. For hepatitis A, the lower incidence of disease arising from an improvement in living conditions leaves a greater number of children, adolescents and young adults susceptible to residual circulating virus. Consequently, initial infection occurs later in life when clinical illness is more frequent and the rate of morbidity and mortality higher. Although both viruses differ greatly, including their modes of transmission, the overlap in their epidemiology warrants the combination of hepatitis A and B vaccination. The immune response elicited by the combined hepatitis A and B vaccine following a three-dose schedule compares well with the anti-hepatitis A virus (HAV) and anti-hepatitis B sero-responses obtained with monovalent vaccines. In addition, it was shown that the seroprotection rate for anti-hepatitis B increased more rapidly with the administration of the combined vaccine, with values of more than 80% within 1 month after the first two doses (schedule, 0, 1 and 6 months). Currently, according to the World Health Organization recommendations, more than 116 countries are vaccinating their infants and/or adolescents against hepatitis B. Recently, several countries were considering or have decided to begin mass vaccination against HAV (more than fifteen states in the US, Spain (Catalonia), Italy (Puglia)). For these countries, the combination of hepatitis A and B antigens in one single vaccine offers the following advantages: fewer injections for protection against two infections, better compliance, lower implementation costs, and fewer missed vaccination opportunities. Further simplification of the schedule, by reducing the number of doses, would improve the compliance rate as well as being more convenient for the vaccinee. This should translate into a reduction in costs associated with vaccine administration. In some recent vaccine studies, the immunogenicity and safety profile of a two-dose schedule (0 and 6 months) of the adult formulation of the combined hepatitis A and B vaccine was investigated in children aged 1-11 years, as well as in adolescents aged 12-15 years. Current results indicate that this two-dose schedule of the adult formulation could be considered a viable alternative for immunization of children and adolescents.