A pilot model of vaccination against hepatitis B virus suitable for mass vaccination campaigns in hyperendemic areas

Prevention of hepatitis B virus infection: from the past to the future

About 3-5 % of the world's population is chronically infected by hepatitis B virus (HBV) and is at risk of developing liver cirrhosis or hepatocellular carcinoma. The risk of dying prematurely because of chronic HBV infection is higher in younger people. The current strategies to prevent HBV infection involve immunization (active and/or passive) and antiviral chemoprophylaxis. The vaccines available for active immunization, containing hepatitis B surface antigen, are safe and confer long-term immunity in most healthy subjects. Since the vaccination is unsatisfactory in some patients, e.g., those with chronic kidney disease, human immunodeficiency virus infection, type I diabetes mellitus, and celiac disease, new strategies of vaccination are required. The neonatal, infant, and adolescent routine program vaccination in about 180 countries has greatly decreased the disease burden. Passive immunization with specific HBV immunoglobulins is recommended after single acute exposure, in infants born to infected mothers, and in HBV-infected patients undergoing liver transplantation combined with nucleoside/nucleotide analogues (chemoprophylaxis). Chemoprophylaxis is also indicated in HBV carrier candidates for immunosuppressive treatment and in patients with occult B infection undergoing immunosuppressive therapy or hematopoietic stem cell transplantation. Since HBV is not eradicable by an immune response or by antiviral drugs developed so far, the only preventive strategy remains global neonatal vaccination in all countries, firstly in HBV-endemic countries.

Impact of hepatitis B vaccination in a highly endemic area of south Italy and long-term duration of anti-HBs antibody in two cohorts of vaccinated individuals

The aims of this study were to evaluate the impact of hepatitis B vaccination on the changing pattern of HBV infection in a former hyperendemic area (Afragola, South Italy), and to assess the long-term persistence of anti-HBs in two cohorts of individuals vaccinated as infants 18 and 23 years ago. Our data shows a significant decline in the prevalence of hepatitis B virus (HBV) markers in the general population from 1978 to 2006 (HBsAg: 13.4% versus 0.91%; anti-HBc: 66.9% versus 7.6%; p<0.001). Data from two cohorts of vaccinees provides further evidence regarding the long-term persistence of vaccine-induced anti-HBs. Data here reported indicates that the implementation of vaccination had a great impact in the control and prevention of hepatitis B in Italy.

Hepatitis B vaccination in a hyper-endemic tribal community from India: assessment after three years

Hepatitis B infection is highly endemic among the primitive tribes of Andaman and Nicobar Islands, India and it is necessary to initiate hepatitis B vaccination for control of this infection. A pilot project of mass hepatitis B vaccination using indigenously developed vaccine was initiated among Nicobarese tribe of Car Nicobar Island. Sero-protection rates after second and third year were 89% and 85.5%, respectively. The rate of chronic infection in the vaccinated population after three years was 1.86% compared to the pre-vaccination rate of 20.7%. Considering high sero-protection rates and low cost, the indigenous vaccine could be used for vaccination programme in this tribal community.

Economic analysis of promotion of hepatitis B vaccinations among Vietnamese-American children and adolescents in Houston and Dallas

OBJECTIVE

To ascertain the cost-effectiveness and benefit-cost ratios of 2 public health campaigns conducted in Dallas and Houston in 1998-2000 for "catch-up" hepatitis B vaccination of Vietnamese-Americans born 1984-1993.

DESIGN

Program evaluation.

SETTING

Houston and Dallas, Texas.

PARTICIPANTS

A total of 14,349 Vietnamese-American children and adolescents.

INTERVENTIONS

Media-led information and education campaign in Houston, and community mobilization strategy in Dallas. Outcomes were compared with a control site: Washington, DC.

MAIN OUTCOME MEASURES

Receipt of 1, 2, or 3 doses of hepatitis B vaccine before and after the interventions, costs of interventions, cost-effectiveness ratios for intermediate outcomes, intervention cost per discounted year of life saved, and benefit-cost ratio of the interventions.

RESULTS

The number of children who completed the series of 3 hepatitis B vaccine doses increased by 1176 at a total cost of 313,904 dollars for media intervention, and by 390 and at 169,561 dollars for community mobilization. Costs per child receiving any dose, per dose, and per completed series were 363 dollars, 101 dollars, and 267 dollars for media intervention and 387 dollars, 136 dollars, and 434 dollars for community mobilization, respectively. For media intervention, the intervention cost per discounted year of life saved was 9954 dollars and 131 years of life were saved; for community mobilization, estimates were 11,759 dollars and 60 years of life. The benefit-cost ratio was 5.26:1 for media intervention and 4.47:1 for community mobilization.

CONCLUSION

Although the increases in the number of children who completed series of 3 doses were modest for both the Houston and Dallas areas, both media education and, to a lesser degree, community mobilization interventions proved cost-effective and cost-beneficial.

Comparison of hepatitis B vaccine coverage and effectiveness among urban and rural Mongolian 2-year-olds

BACKGROUND

The prevalence of hepatitis B (HBV) carriage in Mongolia is reported to be 14%. Universal HBV immunization of newborns has been shown to decrease carriage in Asian populations. Mongolia began universal newborn vaccination in 1991. This evaluation of vaccine coverage and effectiveness compares the success of the program between urban and nomadic rural populations.

METHODS

Using random cluster sampling, 148 Mongolian 2-year-olds from seminomadic rural families were compared with 127 2-year-olds from Ulaanbaatar, the capital city.

RESULTS

More than 95% of all subjects received hepatitis B vaccine although rural subjects were less likely to complete the series than were urban subjects. Adequate vaccine response differed significantly: 94.2% of urban subjects versus only 70.2% of rural subjects had protective anti-HBs levels (P < 0.001). Overall the proportion of hepatitis B infection in both samples was lower than the historical Mongolian prevalence. However, unexpectedly 40% of subjects in rural Bayanhongor Aimag (Province) were found to be HBsAg positive.

CONCLUSION

The Mongolian infant vaccination program for hepatitis B is successfully reducing the rate of chronic carriage in the immunized generation. However, vaccine response among rural subjects is less than that among urban. There appears to be a pocket of high disease prevalence in Bayanhongor that requires further study.

Analysis of the relationship between immunogenicity and immunity for viral subunit vaccines

The prevention of viral infection by vaccination relies on stimulating an appropriate immune response in order to reduce the probability with which a virus can establish an infection. Post-vaccination antibody responses have therefore been associated with reducing the probability with which an individual can be infected (i.e., the vaccine's "impact"). Quantifying this relationship is essential in evaluating new vaccines, especially since comparisons between vaccines, and vaccine licensure, may be dependent on antibody responses alone. In this paper two principal questions are identified which need to be addressed in the evaluation of subunit vaccines: i) how do specific antibody levels relate to complete protection from infection or disease and ii) how do antigenic subunits interact in developing protection when combined together in a single vaccine. The aim is to identify explicitly certain assumptions that are frequently made implicitly in the discussion of vaccine action. First, antibody levels are related to levels of protection through a novel statistical analysis of incidence data from a published hepatitis B vaccine trial. The antibody response observed after influenza A virus infection is discussed in relation to the selection of neutralisation escape variants. Finally, by way of example, a theoretical situation is examined and three simple models of subunit vaccine action are constructed in order to describe how antibody levels may be related to population level phenomena such as the elimination of an infection by mass vaccination.

Immunization programme against hepatitis B virus infection in Italy: cost-effectiveness

In Italy in the 1980s the extent of viral hepatitis B infection was on average about 11,000 symptomatic cases of acute viral hepatitis (AVH) per year (19/100,000 inhabitants). The prevalence of HBsAg carriers in the general population was about 3% and in pregnant women 2.4%. 64,000 people were affected by chronic viral hepatitis (CVH) or cirrhosis (prevalence rate 112/100,000) and 3400 by hepatocellular carcinoma (HCC) (prevalence rate 5.9/100,000). To reduce these HBV related pathologies in the Italian population, universal vaccination of newborn babies, 12-year old adolescents and high risk groups was implemented in 1991. The annual cost of this immunization is about 57 million 544 thousand USD: direct costs: 41 million 34 thousand USD; indirect costs: 16 million 510 thousand USD. Concerning the vaccination impact on HBV endemicity in Italy, we found a significant reduction of acute viral hepatitis incidence (4.2/100,000 in 1996 versus 19/100,000 in the '80s) and HBsAg carrier prevalence (0.9% in 1997 versus 3% in the '80s). As for the assistance and social cost of acute viral hepatitis occurring from 1991 to 1996 (17,608 cases) it was 238 million 908 thousand USD, while the cost for the same pathology in the years from 1985 to 1990 (35,614 cases) was 483 million 216 thousand USD. Thus, the saving during the years of the vaccination was evaluated in 244 million 308 thousand USD. At the moment, we have no information about the reduction in chronic sequelae of HBV pathology as an effect of the vaccination, because the incidence of this pathology generally starts to appear after 15 years (in our case in 2006).

Long-term epidemiological survey of hepatitis B virus infection in a hyperendemic area (Afragola, southern Italy): results of a pilot vaccination project

In 1983, a pilot project of universal hepatitis B vaccination was introduced in a hyperendemic area in southern Italy (Afragola) and is ongoing to date. In this area before the start of vaccination, we found significant evidence of HBV endemicity: the acute viral hepatitis B incidence in the general population averaged 63/100,000; the HBsAg and anti-HBc prevalence rates were 13.4% and 66.9%, respectively; there was involvement of hepatitis B virus (HBV) in 48.1% of chronic liver pathologies (46.3%) in chronic viral hepatitis, 49.5% in cirrhosis and 71.7% in hepatocellular carcinoma cases). We studied the acute viral hepatitis incidence during the vaccination period from 1983 to 1997 and compared the HBsAg and anti-HBc prevalences in 1978 to those in 1997, after 15 years of vaccination. The HBV-related chronic pathology prevalence was also studied. We found a remarkable drop in the acute viral hepatitis incidence, from an average annually of 63/100,000 in the five years before vaccination to 3/100,000 in the last five years of vaccination. In addition, the HBsAg carrier prevalence in the general population decreased from 13.4% in 1978 to 3.7% in 1997. The percentage dropped in children and adolescents from 6.8% to 0.7%, in young people from 10.2% to 1.1% and in adults from 15.8% to 4.0%. The anti-HBc carrier prevalence, found to be 66.9% in 1978, was 34.2% in 1997. Finally, we found a much less significant involvement of HBV in chronic liver pathologies; in fact, it was present in only 18.2% of cases in 1997 and in 48.2% in 1982. In the light of the data, we can assert that universal hepatitis B vaccination has had a substantial effect on HBV endemicity in the Afragola area. We believe that the reduction found in the incidence of acute viral hepatitis B and HBV-related chronic liver pathologies is connected to the decrease in HBV carriers in the area, which therefore reduces the risk of contagion for the unvaccinated.

A simplified schedule to integrate the hepatitis B vaccine into an expanded program of immunization in endemic countries

OBJECTIVE

To investigate the safety, immunogenicity, and efficacy of a simplified hepatitis B vaccination schedule.

METHODS

The second dose of hepatitis B vaccine and the first dose of diphtheria-tetanus-pertussis (DTP) vaccine were given simultaneously at age 6 weeks. The second dose of DTP vaccine was given at age 3.5 months. The third dose of DTP vaccine and the third dose of hepatitis B vaccine were given at age 5.5 months. One hundred three infants (group A) born to mothers without hepatitis B surface antigen (HBsAg) received DTP with whole-cell pertussis vaccine. Fifty-five infants (group B) born to mothers with HBsAg and hepatitis B e antigen received DTP with acellular pertussis vaccine.

RESULTS

By age 9 months, none of group A and 4 (7%) group B infants were sero-positive for HBsAg. The protective efficacy against the hepatitis B carrier state in these infants at high risk was 92%. Antibody to hepatitis B surface antigen was 10 mlU/ml or greater in 99 (96%) of group A infants and in 50 (91%) of group B infants. Both the acellular and whole-cell DTP vaccines were immunogenic, and the incidences of adverse reactions were within an expected and acceptable range.

CONCLUSIONS

The simplified vaccination schedule to integrate the hepatitis B vaccine into the Expanded Programme of Immunization was safe, Immunogenic, and effective. This schedule may improve vaccine compliance and be applied to DTP and hepatitis B combination vaccines now under investigation.

Integration of hepatitis B vaccination into the expanded programme on immunization in Chonburi and Chiangmai provinces, Thailand

Hepatitis B (HB) immunization was introduced as part of the expanded programme on immunization (EPI) in two provinces in Thailand and evaluated over a four year period. Three doses of HB vaccine were offered to 60,980 newborns at birth, 2 and 6 months of age. The overall coverage for complete HB immunization was 90.4%. Serosurveys of randomly selected children under the age of 5 years were undertaken before and at the end of the project. Levels of HBsAg positivity were reduced by 85%, and there was a corresponding 70% increase in protective immunity. These findings demonstrate that HB immunization can be successfully integrated into EPI without adverse effect on coverage rates of other antigens, and results in a marked reduction in the rate of chronic carriage of HB virus in preschool age children.

Hepatitis B vaccination: universal vaccination of newborn babies and children at 12 years of age versus high risk groups. A comparison in the field

From 1983 to 1993 two anti-hepatitis B vaccinal strategies were adopted in two small towns of Southern Italy at high incidence for HBV infections: Afragola (prevalence of HBsAg carriers of 13.4%) and Frattamaggiore (prevalence of HBsAg carriers of 12.9%). In Afragola, the universal vaccination of infants in their first year of life and adolescents at 12 years of age was carried out, while in Frattamaggiore the selective vaccination of high risk groups of population was introduced. During this study, the changes in the HBV infection endemicity in both towns has been tested by monitoring the incidence of new cases of viral hepatitis B and by the prevalence study of HBsAg carriers prior to and 10 years after the beginning of the immunization programme (1978-1993). The results suggest that universal vaccination of infants in the first year of life and adolescents at 12 years of age has a greater efficiency on the improvement on the endemic status of the infection in the general population in comparison with selective vaccination, when the incidence of new cases of disease and the prevalence of number of HBsAg and anti-HBc carriers in the two populations are considered.

Successful mass vaccination against hepatitis B virus in a hyperendemic area in Italy

A pilot model of vaccination against hepatitis B virus suitable for mass vaccination was performed from 1983-1989 in the hyperendemic area of Afragola, a town of 60,000 inhabitants near Naples. In this area of high prevalence of HBsAg carriers, a consistent reduction in the incidence of hepatitis B virus infections as well as chronic related liver complications was observed.