Long-term persistence of immunity to hepatitis B after vaccination during infancy in a country where endemicity is low

Long-term immunogenicity of hepatitis B vaccination in a cohort of Italian healthy adolescents

In 1992, 620 adolescents were vaccinated against hepatitis B. Anti-HBs concentrations were measured in 480 (77.4%) adolescents 1 month after completion of the primary course of vaccination. To assess the persistence of anti-HBs, 347 and 228 of such vaccinees were retested for anti-HBs in 1999 and for anti-HBs and anti-HBc in 2003. More than 10 years after vaccination, individuals with anti-HBs >or=10 mIU/ml were considered protected while those with antibody <10 mIU/ml were given a booster dose and retested 2 weeks later. Check performed in 2003 showed that 208/228 (91.2%) vaccinees retained protective concentrations of anti-HBs. All vaccinees were anti-HBc negative. 11 of the 12 (91.7%) individuals who were given a booster dose of vaccine showed a vigorous anamnestic response while the remaining one showed a weak response (10.6 mIU/ml). These data suggests that hepatitis B vaccination can confer long-term immunity and that immunological memory can outlast the loss of antibody. Hence, the use of routine booster doses of vaccine does not appear necessary to maintain long-term protection in successfully vaccinated immunocompetent individuals.

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Long-term immunogenicity of hepatitis B vaccination and policy for booster: an Italian multicentre study

BACKGROUND

Universal anti-hepatitis-B vaccination of infants and adolescents was implemented in Italy in 1991. We undertook a multicentre study in previously vaccinated individuals to assess the duration of immunity and need for booster, over 10 years after vaccination.

METHODS

In 1212 children and 446 Italian Air Force recruits vaccinated as infants and adolescents, respectively, we measured the concentrations of antibodies to hepatitis-B surface antigen (anti-HBs) and the presence of antibodies to hepatitis-B core antigen (anti-HBc) at enrollment; postimmunisation values were not available. Individuals positive for anti-HBc were tested for hepatitis B surface antigen (HBsAg) and hepatitis B viral DNA. Individuals with anti-HBs concentrations at 10 IU/L or more were regarded as protected; those with antibody less than 10 IU/L were given a booster dose and retested 2 weeks later. Individuals showing postbooster anti-HBs concentrations of less than 10 IU/L were offered two additional vaccine doses and retested 1 month after the third dose.

FINDINGS

Protective anti-HBs concentrations were retained in 779 (64%, 95% CI 61.6-67) children and 398 (89%, 86.4-92.1) recruits. We recorded antibody amounts of less than 10 IU/L in 433 children (36%, 33-38.4) and 48 (11%, 7.9-13.6) recruits. One child and four recruits were positive for anti-HBc, but negative for HBsAg and hepatitis B viral DNA. Antibody concentrations were higher in recruits than in children (geometric mean titre 234.8 IU/L vs 32.1 IU/L, p=0.0001). 332 (97%) of 342 children and 46 (96%) of 48 recruits who received a booster showed an anamnestic response, whereas ten (3%) children and two (4%) recruits remained negative for anti-HBs or had antibody concentrations of less than 10 IU/L. Prebooster and postbooster antibody titres were strongly correlated with each other in both groups. All individuals given two additional vaccine doses (eight children and two recruits) showed anti-HBs amounts of more than 10 IU/L at 1 month after vaccination.

INTERPRETATION

Strong immunological memory persists more than 10 years after immunisation of infants and adolescents with a primary course of vaccination. Booster doses of vaccine do not seem necessary to ensure long-term protection.

Hepatitis B surface antigen-specific T and B cell memory in individuals who had lost protective antibodies after hepatitis B vaccination

Long-term protection after hepatitis B vaccination is dependent on the persistence of a strong immunologic memory. In search of reliable markers for a hepatitis B surface antigen (HBsAg)-specific immunological memory we studied the cellular and humoral immune responses of 15 healthy individuals who were successfully vaccinated but had lost anti-HBs titers. To determine the reactivity of vaccine-induced HBsAg-specific T cells of both effector and memory phenotype CD4+/CD45RA+ and CD4+/CD45R0+ T cells, respectively, were isolated, stimulated with HBsAg and tested for IFN-gamma and IL-5-secretion by enzyme-linked immunospot assays (Elispot). To detect even small numbers of specific T cells, we enriched the appropriate subpopulation from the entire PBMC population. B cell memory was analysed by cocultivation of isolated B cells with CD4+ T cells and identification of anti-HBs-secreting cells by Elispot. All individuals were revaccinated and humoral and cellular responses were determined. The results showed significant numbers of HBsAg-specific memory T and B cells present in all vaccinees despite the absence of specific antibodies. Our data suggest that individuals who had lost their anti-HBs seropositivity still show immunologic T cell memory and that these T cells are able to trigger anti-HBs production of B cells activated by revaccination.

Persistence of antibody to hepatitis B and protection from disease among Alaska natives immunized at birth

BACKGROUND

Alaska Native (AN) children were at high risk of acquiring hepatitis B virus (HBV) infection before vaccination began in 1983. We evaluated the long-term protection from hepatitis B (HB) vaccination among AN children immunized when infants.

METHODS

During 1984-1995, we recruited a convenience sample of AN children who had received a three dose series of HB vaccine starting at birth and had serum antibody to hepatitis B (anti-HBs) concentrations of >/= 10 mIU/mL at 7-26 months of age. We evaluated anti-HBs concentrations and the presence of anti-HBc in participants' sera every other year up to age 16 years. Anti-HB core antigen (anti-HBc)-positive specimens were tested for hepatitis B surface antigen and for HBV DNA.

RESULTS

We followed 334 children for 3151 person-years (median, 10 years per child) with 1610 specimens collected. Anti-HBs concentrations dropped rapidly among all participants. Among children 2, 5 and 10 years of age, 37 of 79 (47%), 33 of 176 (19%) and 8 of 95 (8%), respectively, had anti-HBs concentrations of >/= 10 mIU/mL. Receipt of recombinant vaccine was significantly associated with a more rapid antibody decline (P < 0.001). Six (1.8%) children acquired anti-HBc, 3 of whom had definite breakthrough infections (at least 2 consecutive anti-HBc-positive specimens or at least 1 anti-HBc-positive specimen and HBV DNA detection by PCR). None of these children had detectable hepatitis B surface antigen, and none had symptoms of hepatitis.

CONCLUSIONS

Anti-HBs concentrations declined over time among AN infants successfully immunized with HB vaccine starting at birth. Transient anti-HBc appeared in a small percentage of children; however, none developed clinical signs of hepatitis or chronic HBV infection.

Hepatitis B vaccination in a school age population: a feasibility study

There remains no consensus on whether to adopt a universal hepatitis B vaccination strategy in the United Kingdom, where the endemicity of hepatitis B virus (HBV) is considered to be very low in the general population. To assess the feasibility and acceptance of a school-based adolescent vaccination approach, 11-13 years old pupils in local secondary schools in the London Borough of Camden and Islington were contacted and offered a three-dose hepatitis B vaccination course using a 0, 1, and 12 months schedule. The adult dose of hepatitis B vaccine (Engerix B GlaxoSmithKline) containing 20 mug recombinant hepatitis B surface antigen (HBsAg) in 1 ml suspension was administered. This dosage is normally intended for adults and children older than 15 years of age, but can be administered in 10-15 years old children when compliance may be low, since a higher proportion of those vaccinated develop protective antibody levels following administration of only two doses of vaccine. Overall, a total of 528 pupils were contacted, with 122 (23%) consenting to be vaccinated. Of these, 117 (96%) received the complete three-dose regimen according to the schedule (four did not receive vaccine: three were non-attendees and one was previously vaccinated; one withdrew following a flu-like adverse event). The results of this study show that it is feasible and practical to administer hepatitis B vaccination to adolescents in a school setting, and that it is possible to achieve high rates of uptake for the complete three-dose course among adolescents. However, in order to attain and sustain high coverage rates among pupils, this would require additional general health promotion, including health education and provision of information, targeting of teachers, pupils, and parents in order to increase participation in a school-based hepatitis B vaccination programme. A further requirement includes the availability of good local health support within schools so as to allow for an efficient vaccine delivery system to maximize vaccination in this setting.

Hepatitis B virus and hepatitis C virus infections in children

PURPOSE OF REVIEW

To analyse the most relevant recent information on efficacy, duration and coverage of anti-hepatitis B virus vaccination; correlates of mother-to-child hepatitis C virus transmission; the natural history and outcomes of hepatitis B and C virus infections in children; the efficacy and safety of specific therapies.

RECENT FINDINGS

Insufficient hepatitis B virus vaccine coverage and incomplete or delayed vaccine cycles need improvement in many countries. Hepatitis B virus mutants may explain some fulminant hepatitis in perinatally infected infants and vaccine failures. No interventions to prevent vertical hepatitis C virus transmission have been identified. Spontaneous clearance of hepatitis B is lower in children than in adults, while the rates appear to be similar for hepatitis C. The disease progression is slower for both infections in childhood. Several studies support the efficacy and safety of interferons and lamivudine in chronic hepatitis B or of interferons and ribavirin in chronic hepatitis C in children, but the optimal therapy remains unclear.

SUMMARY

There are doubts as to the long-term persistence of anti-hepatitis B immunization in low-endemicity areas. Routine hepatitis C virus testing in pregnancy is not recommended as there are no available prophylactic measures. Although hepatitis B and C virus infections are usually asymptomatic or with mild manifestations in childhood, concerns around their long-term clinical impact suggest the need for early treatment. Children should preferably be treated in the context of targeted trials for a better understanding of the efficacy and tolerance of drugs currently used in adults.

Long-term efficacy of hepatitis B vaccine, booster policy, and impact of hepatitis B virus mutants

The long-term efficacy of hepatitis B vaccine, long-term effectiveness of hepatitis B immunisation programmes, immune memory induced by hepatitis B vaccine, current booster policies, and impact of hepatitis B virus mutants on immunisation programmes were reviewed at the Viral Hepatitis Prevention Board (VHPB) meeting in Sevilla, Spain, March 2004. The main focus was on universal vaccination programmes with data being presented from Italy, Saudi Arabia, Singapore, Spain, Taiwan, Thailand, The Gambia, and USA (Alaska).

Sexual transmission of hepatitis B

PURPOSE OF REVIEW

Hepatitis B virus infection is prevalent worldwide and is a significant cause of morbidity and mortality particularly in Asia. Adults chronically infected with hepatitis B virus remain a significant potential source of sexually transmitted hepatitis B. The purpose of this article is to review the recent literature relating to hepatitis B virus transmission with particular emphasis on sexual transmission and efforts to prevent spread.

RECENT FINDINGS

The introduction of hepatitis B virus vaccine and the implementation of universal childhood vaccination for hepatitis B in some countries have led to a dramatic reduction in the number of children with chronic hepatitis B. However, recent reports suggest that we are not as successful in preventing infection by sexual transmission. It is clear that sexual transmission of hepatitis B virus is still widespread and is a major problem in certain high-risk groups such as men who have sex with men, intravenous drug users, prisoners and sex workers. Significant problems remain with respect to education and vaccination within these groups.

SUMMARY

Hepatitis B virus remains a major health burden but it is preventable by education and vaccination. Greater resources are required to expand vaccination to the at-risk, sexually active adult populations if the World Health Organization ideal of hepatitis B virus eradication is to be realized and the burden of hepatitis B virus-related morbidity and mortality contained.