The vaccinal prophylaxis of hepatitis B in Russia--the achievements, problems and outlook

Certain specific features of the present epidemic situation with hepatitis B (HB) in Russia were established: significant growth of HB morbidity, starting from 1995; the prevalence of persons aged 15-29 years among HB patients, which was linked with the sharp activation of the sexual route of the transmission of HB virus in recent years; an essential increase in the number of patients having contacted this virus in the process of the intravenous use of drugs. The results of the use of vaccine "Engerix B" among persons belonging to different risk groups were considered (a decrease in HB morbidity among them by 8-19 times was noted), the study demonstrated high immunogenicity anti-HBs antibodies on protective titers were determined in 92.3-95.7% of the vaccinees) and low reactogenicity of the vaccine, as well as stable postvaccinal immunity (5 years after the course of vaccination was completed anti-HBs antibodies were retained in 70.6-74% of the vaccinees). The study showed that only the vaccination of adolescents in combination, in the presence of opportunity, with the immunization of newborn infants and young children in the first year of their life made it possible to produce an essential effect on the activity of the epidemic process. Already in 2 years such organization of work on the prophylaxis of HB in one of the cities of the Sverdlovsk region led to a decrease in HB morbidity by 2.9 times, and among adolescents 9 times.     

Experience with vaccine prophylaxis of hepatitis B among different groups of children

The immunological activity of different vaccines against hepatitis B was evaluated in the Hepatological Center organized on the basis of the Infectious Hospital in Tula. Newborn infants were immunized with the use of the following vaccines: Engerix B (Belgium), Combiotech (Russia), Euvax B (Aventis Pastèur, South Korea). Altogether, after the full course of immunization anti-HBs were detected in 76 children out of 81 (in 93.8%). Vaccine Engerix B, when introduced according to the schedule 0-1-2-12 months, exhibited high immunogenic properties in a group of infants born of women with persistent HBs-antigenemia. Anti-HBs at a concentration exceeding 1000 I.U./I could be detected in 84.6%. In another group of children immunized according to the schedule 0-1-6 months first with vaccine Combiotech at the age of 0 and 1 month, then (at the age of 6 months) with vaccine Euvax, the presence of postvaccinal anti HBs at protective concentration was registered in all children. After immunization against hepatitis B with the use of all above-mentioned vaccines introduced according to both schedules high immunological activity and safety of immunization were noted.     

Evaluation of the reactogenicity and immunogenic potency of combined vaccine "Bubo-Kok" in the immunization of children against diphtheria, tetanus, pertussis and viral hepatitis B

Combined vaccine "Bubo-Kok" is characterized by safety and high immunological activity. The number of postvaccinal reactions in children aged 1 and 2 years, immunized with vaccine "Bubo-Kok", was not statistically different from those in groups of children immunized with adsorbed DPT vaccine, as well with such vaccine in combination with vaccine against hepatitis B. After the completion of the primary course of immunization 100% of children had protective antibody titers against diphtheria, tetanus and hepatitis B. Antibody titers against pertussis, equal to or exceeding protective titers, were found in more than 70% of immunized children. The immunogenic potency of vaccine "Bubo-Kok" with respect to all its components was not inferior to that of adsorbed DPT vaccine and vaccine against hepatitis B, when introduced simultaneously in different areas of the body. Vaccine "Bubo-Kok" successfully passed state trials and was recommended for registration.     

含前S蛋白乙肝疫苗免疫人群效果观察

为考核含前Ｓ蛋白乙肝血源疫苗的人群免疫效果,对９６８名ＨＢＶ标志阴性的少年人群以１０μｇ×３的免疫剂量及０、１、２月免疫程序进行接种。全程免疫后一月采血检测其抗－ＨＢｓ免疫应答。结果表明抗－ＨＢｓ阳性率达９６．６％。并对另２９１名抗－ＨＢｃ及ＨＣＶ阳性的少年人群以同样的剂量、同样的免疫程序进行免疫接种,免疫后抗－ＨＢｓ阳性率为９４．１６％,且有２３．９８％的人接种后抗－ＨＢｃ由接种前的阳性转为阴性,全部观察对象无一例检出ＨＢｓＡｇ和其它异常指标     

Evaluation of reactogenicity and immunogenicity of Bubo-M, the Russian combined vaccine for immunization of adults against diphtheria, tetanus and viral hepatitis B

Bubo-M, the first Russian associated vaccine, was found to have low reactogenicity and high immunogenic potency. The frequency of postvaccinal reactions in the group of persons immunized with Bubo-M (20%) appeared to be considerably lower than among persons who received the combined injection of adsorbed DT toxoid with reduced antigen content and vaccine against hepatitis B (47.7%). Following the course of vaccination the level of anti-HBs considerably exceeded the protective level. Immune response to the diphtheria and tetanus components of Bubo-M exceeded that observed after immunization with absorbed DT toxoid with reduced antigen content (p < 0.05).     

Seroepidemiology of hepatitis B virus infection and high rate of response to hepatitis B virus Butang vaccine in adolescents from low income families in Central Brazil

In order to evaluate the seroepidemiology and response to Butang vaccine in adolescents from low income families in Central Brazil, blood samples of 664 adolescents were tested for hepatitis B surface antigen (HBsAg), hepatitis B core antibody (anti-HBc), and hepatitis B surface antibody (anti-HBs) markers, and multiple logistical regression analysis was carried out to determine variables associated with hepatitis B virus (HBV) infection markers. further, three 20 microg Butang vaccine doses were offered to all susceptible individuals (n = 304). Among those who accepted them (n = 182), the seroresponse was evaluated in 170 individuals by quantitative anti-HBs. an overall hbv prevalence of 5.9% was found: four adolescents were HBsAg positive, 24 were anti-HBc, anti-HBs-reactive, and 11 were anti-HBc only. The analyse of risk factors showed that age 16-19 years, place of birth outside Goiás, school B and body piercing were statistically associated with HBV infection markers (p < 0.05). All 170 adolescents responded to Butang, and a geometric mean titer (gmt) of 4344 mUI/ml was obtained. these results reinforce the importance of hepatitis b vaccine in adolescents despite of the hbv regional endemicity, and suggest that three doses of 20 microg of the Butang should guarantee protective anti-hbs levels to individuals at a critical time for hepatitis b acquiring such as latter adolescence and adulthood.     

重庆地区乙肝血清特殊模式患者HBV基因分型及临床自然病程分析

目的了解重庆地区乙肝病毒（HBV）血清学标志物为特殊模式的HBV感染患者病毒基因型的分布情况,分析其临床特征及自然病程。方法从1000例HBV感染者中检测到48例乙肝病毒血清学标志物为特殊模式的患者（HBsAg与抗一HBs同时阳性,HBeAg与抗一HBe同时阳性）。采用巢式聚合酶链式反应（nPCR）对特殊模式患者的HBV进行基因分型,同时对两组特殊模式患者的临床资料和HBV感染的自然史进行分析。结果48例乙肝病毒血清学标志物为特殊模式的HBV感染者中,36例患者HBsAg与抗-HBs同时阳性,12例患者HBeAg与抗-HBe同时阳性。HBeAg＋／抗-HBe＋患者组的年龄较HBsAg＋／抗-HBs＋患者组的小（P〈0．05）。HBsAg＋／抗-HBs＋患者中,3例（8．3％）为B2亚型,12例（33．3％）为c2亚型,21例（58．4％）未分型;HBeAg＋／抗-HBe＋患者中,8例（66．7％）为B2亚型,1例（8．3％）为c2亚型,3例（25．0％）未分型,两组在HBV基因型的分布上差异具有统计学意义（Y2=17．44,P〈0．05）。在HBsAg＋／抗-HBs＋患者中,2例（4．2％）处于免疫清除期,14例（29．2％）处于低复制期,7例（14．6％）处于再活动期。HBeAg＋／抗-HBe＋患者中,5例（10．4％）处于免疫清除期。两组在HBV感染的自然病程中的分布差异具有统计学意义（X2=18．26,P〈0．05）。结论重庆地区乙肝病毒血清学标志物为特殊模式的慢性HBV感染者中,HBeAg与抗-HBe同时阳性的HBV感染者中B2亚型为优势基因型;HBsAg与抗-HBs同时阳性的HBV感染者中,HBV基因型以C2亚型为主。     

Laboratory investigations on "postvaccinall rabies" caused by live sheep-brain vaccine.

The viral ethiology of postvaccinal complications among 30 dogs vaccinated by live antirabies vaccine (Umeno-Doi type, sheep brain vaccine) was fully confirmed. Three lots of virulent vaccine were inoculated subcutaneously into groups of "Wistar" rats according to the different schemes. Between the 1st and 12th day after the end of the vaccination there were no isolations of fixed virus in direct and blind i.c. passages of suspensions made from the thalamus area on succkling mice and rats. Also the viral antigen in the CNS of vaccinated but apparently healthy rats was undetectable. The "postvaccinal rabies" with the next isolation of fixed r.v. in the CNS was developed experimentally in rats only following the subcutaneous injection of the crude sheep-brain's and spinal cord's suspensions--composing the materials to production of antirabies vaccine.     

Transplacentally acquired maternal antibody against hepatitis B surface antigen in infants and its influence on the response to hepatitis B vaccine

Background

Passively acquired maternal antibodies in infants may inhibit active immune responses to vaccines. Whether maternal antibody against hepatitis B surface antigen (anti-HBs) in infants may influence the long-term immunogenicity of hepatitis B vaccine remains unknown.

Methodology/Principal Findings

Totally 338 pairs of mothers and children were enrolled. All infants were routinely vaccinated against hepatitis B based on 0-, 1- and 6-month schedule. We characterized the transplacental transfer of maternal anti-HBs, and compared anti-HBs response in children of mothers with or without anti-HBs. In a prospective observation, all 63 anti-HBs positive mothers transferred anti-HBs to their infants; 84.1% of the infants had higher anti-HBs concentrations than their mothers. One and half years after vaccination with three doses of hepatitis B vaccine, the positive rate and geometric mean concentration (GMC) of anti-HBs in 32 infants with maternal anti-HBs were comparable with those in 32 infants without maternal antibody (90.6% vs 87.5%, P = 0.688, and 74.5 vs 73.5 mIU/ml, P = 0.742, respectively). In a retrospective analysis, five and half years after vaccination with three doses vaccine, the positive rates of anti-HBs in 88 children of mothers with anti-HBs ≥1000 mIU/ml, 94 children of mothers with anti-HBs 10–999 mIU/ml, and 61 children of mothers with anti-HBs <10 mIU/ml were 72.7%, 69.2%, and 63.9% (P = 0.521), respectively; anti-HBs GMC in these three groups were 38.9, 43.9, and 31.7 mIU/ml (P = 0.726), respectively.

Conclusions/Significance

The data demonstrate that maternal anti-HBs in infants, even at high concentrations, does not inhibit the long-term immunogenicity of hepatitis B vaccine. Thus, current hepatitis B vaccination schedule for infants will be still effective in the future when most infants are positive for maternal anti-HBs due to the massive vaccination against hepatitis B.     

广州市1992-2007年出生新生儿接种乙型肝炎疫苗免疫效果评估

为评估广州市新生儿乙型肝炎疫苗(HepB)接种纳入计划免疫管理后免疫效果。对1992-2007年出生并接种HepB的新生儿2877人,按1992-2001年和2002-2007年出生新生儿分为计划免疫管理前(Ⅰ组)、计划免疫管理后(Ⅱ组)2组,采血检测乙肝病毒表面抗原(HBsAg)、乙肝病毒表面抗体(抗-HBs)和乙肝病毒核心抗体(抗-HBc)。Ⅱ组HBsAg阳性率为0.48%比Ⅰ组的4.54%阳性率下降了80.65%,在统计学意义上有显著差异。抗-HBc阳性率也由36.07%下降为26.73%,Ⅱ组的抗-HBs阳性率为75.19%,高于I组水平。新生儿乙型肝炎疫苗纳入计划免疫管理后群体免疫效果良好,使用不同种类乙肝疫苗效果没有统计学差异。重组(酵母)乙型肝炎疫苗有较好的近期保护效果和免疫原性,与以前使用血源乙型肝炎疫苗效果相当。     

Coexistence of hepatitis B surface antigen (HBs Ag) and anti-HBs antibodies in chronic hepatitis B virus carriers: influence of "a" determinant variants

In chronic hepatitis B (CHB), the persistence of hepatitis B surface antigen (HBs Ag) is sometimes associated with antibodies (Ab) to HBs (anti-HBs). To assess the hypothesis of the selection of HBs Ag immune escape variants in CHB patients, the variability of the HBV S gene was determined for patients persistently carrying both HBs Ag and anti-HBs antibodies and patients solely positive for HBs Ag. We selected 14 patients who presented both markers (group I) in several consecutive samples and 12 patients positive for HBs Ag only (group II). The HBs Ag-encoding gene was amplified and cloned, and at least 15 clones per patient were sequenced and analyzed. The number of residue changes within the S protein was 2.7 times more frequent for group I than for group II patients and occurred mostly in the "a" determinant of the major hydrophilic region (MHR), with 9.52 versus 2.43 changes per 100 residues (P = 0.009), respectively. Ten patients (71%) from group I, but only three (25%) from group II, presented at least two residue changes in the MHR. The most frequent changes in group I patients were located at positions s145, s129, s126, s144, and s123, as described for immune escape variants. In CHB patients, the coexistence of HBs Ag and anti-HBs Ab is associated with an increase of "a" determinant variability, suggesting a selection of HBV immune escape mutants during chronic carriage. The consequences of this selection process with regard to vaccine efficacy, diagnosis, and clinical evolution remain partially unknown.     

Seropositivity for hepatitis B virus, vaccination coverage, and vaccine response in dentists from Campo Grande, Mato Grosso do Sul, Brazil

This study investigated the seropositivity for hepatitis B virus (HBV), the vaccination index, and the vaccine response index in dentists from Campo Grande, MS. Blood samples from 474 dentists (63.7% women and 36.3% men), with a mean age of 38.5 +/- 10.5 years were analyzed by enzyme-linked immunosorbent assay to detect the serological markers: HBsAg, anti-HBs, and anti-HBc. The HBsAg positive samples were tested for anti-HBc IgM, HBeAg, and anti-HBe. A total of 51 (10.8%) dentists showed seropositivity for HBV. Three (0.6%) were HBsAg/anti-HBc/anti-HBe positive, 43 (9.1%) were anti-HBc/anti-HBs positive, and 5 (1.1%) had only anti-HBc. Viral DNA was detected by polymerase chain reaction in 9 (17.6%) out of 51 HBV seropositive samples. A vaccination index of 96.6% (458/474) was observed, although 73.1% (335/458)completed the three-dose schedule. Excluding 46 HBV seropositive individuals from 458 that reported vaccination, 412 were analyzed for vaccine response index. It was observed that 74.5% (307/412) were anti-HBs positive; this percentage increased to 79.1% when three doses were administered. The results showed a high vaccination index and a good rate of vaccine response; however, the failure in completing the three-dose schedule and the occurrence of HBV infection reinforce the need for more effective prevention strategies.     

Multicenter study on the immunogenicity and safety of two recombinant vaccines against hepatitis B

The immunogenicity and safety of a new recombinant hepatitis B vaccine from the Instituto Butantan (Butang) were evaluated in a multicenter, double-blind, prospective equivalence study in three centers in Brazil. Engerix B was the standard vaccine. A total of 3937 subjects were recruited and 2754 (70%) met all protocol criteria at the end of the study. All the subjects were considered healthy and denied having received hepatitis B vaccine before the study. Study subjects who adhered to the protocol were newborn infants (566), children 1 to 10 years old (484), adolescents from 11 to 19 years (740), adults from 20 to 30 years (568), and adults from 31 to 40 years (396). Vaccine was administered in three doses on the schedule 0, 1, and 6 months (newborn infants, adolescents, and adults) or 0, 1, and 7 months (children). Vaccine dose was intramuscular 10 microg (infants, children, and adolescents) or 20 microg (adults). Percent seroprotection (assumed when anti-HBs titers were > 10 mIU/ml) and geometric mean titer (mIU/ml) were: newborn infants, 93.7% and 351.1 (Butang) and 97.5% and 1530.6 (Engerix B); children, 100% and 3600.0 (Butang) and 97.7% and 2753.1 (Engerix B); adolescents, 95.1% and 746.3 (Butang) and 96% and 1284.3 (Engerix B); adults 20-30 years old, 91.8% and 453.5 (Butang) and 95.5% and 1369.0 (Engerix B); and adults 31-40 years old, 79.8% and 122.7 (Butang) and 92.4% and 686.2 (Engerix B). There were no severe adverse events following either vaccine. The study concluded that Butang was equivalent to Engerix B in children, and less immunogenic but acceptable for use in newborn infants, adolescents, and young adults.     

不同来源血浆对静注人免疫球蛋白中抗-HBs、白喉抗体效价的影响

调查分析不同来源原料血浆对静注免疫球蛋白(IVIG)制品内的抗-HBs、白喉抗体效价的影响。选择6个单采血浆站,对其提供的血浆为原料制备的IVIG所含的抗-HBs抗体、白喉抗体效价进行了测定。检测结果显示,用A、B、C、D、E、F编号的6个相应血浆站采集的血浆为原料制备成IVIG其抗-HBs抗体(IU/g)效价分别为33.77、103.95、70.94、132.45、78.84、58.28;白喉抗体平均效价分别为5.17、7.36、4.26、7.67、10.14、9.24。6个单采血浆站间的IVIG制品中白喉抗体效价无明显差异,但抗-HBs效价却存有显著差异。     

Intradermal vaccination of adults with three low doses (2 micrograms) of recombinant hepatitis B vaccine. I. Seroconversion rate and adverse effects

A total of 250 dentists (53.6% men and 46.4% women), with a mean age of 35.1 +/- 9.8 years, were submitted to serological tests for the diagnosis of hepatitis B (HB)--HBsAg, anti-HBs, anti-HBc, HBeAg, and anti-HBe--using a radioimmunoassay. One or more of these markers were detected in 78 individuals (31.2%) who were excluded from the group to be vaccinated. Of the 172 HB-susceptible individuals, 135 (78.5%) responded to the call and were intradermally injected with three 2 micrograms doses of the Belgian HB recombinant vaccine, applied at an interval of one month between the 1st and 2nd dose and of five months between the 2nd and 3rd dose. A new determination of HB markers carried out 50 days after the 3rd dose showed that 110 (81.5%) individuals had become anti-HBs positive (65.5% good responders and 34.5% poor responders). Mean serum anti-HBs titer of these 110 dentists was 42.4 U S/N, similar in both sexes. The adverse effects analyzed in 106 dentists were: (a) local: pain (12.3%), burning sensation (14.1%), pruritus (25.5%), erythema (28.3%), local heat (18.9%), and a hypochromic spot (32.1%); (b) systemic (4.7%): discomfort in two patients, and fever, anorexia, and asthenia in one patient each. Intradermal administration of a fourth 2 micrograms vaccine dose to 39 dentists (poor or non-responders) increased the total number of anti-HBs-positive individuals from 110 (81.5%) to 114 (84.4%), with the number of good responders increasing from 72 (65.5%) to 85 (74.6%). We conclude that the Belgian recombinant vaccine applied in the scheme used here induces a high rate of seroconversion and causes only mild and transitory adverse effects.     

钦南区1～6岁儿童乙肝及白喉疫苗免疫效果分析

目的分析钦南区儿童乙肝及白喉疫苗接种后的免疫效果,为该地区儿童免疫规划工作提供科学依据。方法采用整群随机抽样方法,选取5个乡镇1~6岁常住儿童151名为调查对象,进行病毒性乙型肝炎(乙肝)、白喉血清学检测,并对结果进行分析。结果 HBsAg阳性2人,阳性率1.32%;抗-HBs阳性112人,阳性率74.17%。白喉IgG阳性142人,阳性率94.04%。抗-HBs中位数21.32 mIU/mL,白喉IgG中位数0.14 mIU/mL,乙肝疫苗首针及时接种率83.44%;男女抗-HBs阳性率、白喉IgG阳性率、抗体中位数差异均无统计学意义(P0.05),抗-HBs阳性率、白喉IgG阳性率随年龄的增长而下降(P0.01)。结论钦南区1~6岁儿童乙肝疫苗接种率、首针及时接种率均达到了国家免疫规划的目标,白喉IgG阳性率维持较高的水平,但HBsAg阳性率略高于国家免疫规划的目标,儿童免疫规划工作仍需进一步加强。     

Protection against hepatitis B by the Butang recombinant vaccine in newborn children in South Brazil

The prevention of hepatitis B by vaccination is one of the most efficient tools to avoid the transmission of the virus. This study evaluated the immunogenicity of the national vaccine Butang in children born in Campo Mour?o City, state of Paraná, Brazil, aged 7 to 12 months, by determining the anti-HBsAg antibodies levels after completion of the National Immunization Program Protocol for hepatitis B. All 70 children evaluated by the MEIA method (immune-enzymatic micro particles) showed seroconversion to the Butang vaccine. Nine children (12.9%) presented a low response, with anti-HBs titers between 11 and 100 mUI/ml; 39 children (55.7%) showed a good response to the vaccine, with titers between 101 and 1000 mUI/ml; and 22 children (31.4%) showed antibodies titers higher than 1000 mUI/ml. The mean titer of the anti-HBs antibody titers was 1408.1 +/- 2870.26 mUI/ml (15.7 to 19560.0 m UI/ml). The levels of antibodies produced by the prematurely-born children were not statistically different from those found in the newborns. Fifty-five children were also evaluated through the ELFA method (ELISA with a final detection in fluorescence), which presented similar results. The results obtained in our study corroborated the effectiveness of the national vaccine Butang in newborn children of Campo Mour?o City, Paraná, even if they were premature.     

The positive rates of hepatitis B surface antibody in youth after booster vaccination: a 4-year follow-up study with large sample

Background: Hepatitis B virus (HBV) infection is still a public issue in the world. Hepatitis B vaccination is widely used as an effective measure to prevent HBV infection. This large-sample study aimed to evaluate the positive rates of hepatitis B surface antibody (anti-HBs) in youth after booster vaccination.Methods: A total of 37788 participants were divided into two groups according to the baseline levels of anti-HBs before booster vaccination: the negative group (anti-HBs(−)) and the positive group (anti-HBs(+)). Participants were tested for anti-HBs levels after receiving a booster vaccine at 1 and 4 years.Results: The positive rates of anti-HBs were 34.50%, 73.80% and 67.32% before booster vaccination at 1 and 4 years after vaccination, respectively. At 4 years after the booster vaccination, the positive rates of 13–18 years were 47.54%, which was the lowest level among all youth age groups. In the anti-HBs(−) group, the positive conversion rates of anti-HBs were 74.62% at 1 year after receiving a booster vaccine, and 67.66% at 4 years after vaccination. In the anti-HBs(+) group, the positive maintenance rates of anti-HBs were 70.16% after 1 year, and 66.66% after 4 years. Compared with the baseline anti-HBs (+) group, the positive rates of the baseline anti-HBs(−) group were higher at 1 and 4 years after receiving the booster vaccine.Conclusion: The positive rates of anti-HBs declined over time, especially the positive maintenance rates were the lowest at age of 13–18 years.     

HBsAg阴性母亲及其婴儿乙肝疫苗接种情况和免疫效果研究

目的：了解乙肝表面抗原阴性（HBsAg阴性）母亲及其婴儿乙肝疫苗接种情况及抗-HBs滴度水平,从而为今后针对该特殊人群进行更好的乙肝疫苗免疫策略提供依据。方法：2010年5月～2010年10月,对陕西省227对HBsAg阴性母亲及其婴幼儿（月龄为8～24月）进行流行病学调查并采集血液标本,对母婴血清抗-HBs进行定性及定量检测。结果：母亲乙肝表面抗体（抗-HBs）阳性率为45.4%,抗-HBs平均滴度为12.88 mIU/mL（95%CI：8.91-18.19）。婴儿乙肝疫苗首针、第二针和第三针的及时接种率分别为95.2%,93.8%和85.9%。婴儿抗-HBs阳性率为77.1%,抗-HBs平均滴度为37.15 mIU/mL（95%CI：28.18-48.98）。结论：婴儿乙肝疫苗首针及时接种率较高,但三针全程及时接种率仍需提高。母亲抗-HBs阳性率较低,应当重视HBsAg阴性孕龄妇女的乙肝疫苗接种及乙肝标志物的检测,从而提高该人群的乙肝免疫水平。     

Intradermal vaccination of adults with three low doses (2 micrograms) of recombinant hepatitis B vaccine. II. Persistence of immunity and induction of immunologic memory

Of the 110 dentists who had presented seroconversion 50 days after the intradermal application of three 2 micrograms doses of the Belgian recombinant vaccine against hepatitis B (HB), administered eight years before at an interval of one month between the 1st and 2nd doses and of five months between the 2nd and 3rd doses, 51 were included for the assessment of the persistence of immunity. None of the dentists had hepatitis or had received HB vaccine during this period. All subjects were submitted to serological tests for the detection of the following markers of hepatitis B virus (HBV) infection: HBsAg, anti-HBc, HBeAg, anti-HBe, and anti-HBs, with no HBsAg, anti-HBc, HBeAg or anti-HBe being detected. A microparticle enzyme immunoassay (MEIA) revealed the presence of anti-HBs at protective titers (> or = 10 mIU/ml) in 42 dentists (82.4%), with the anti-HBs titer being higher than 100 mIU/ml in 36 of them (70.6%) (good responders), between 10 and 100 mIU/ml in 6 (11.8%) (poor responders), and lower than 10 mIU/ml in 9 (17.6%) (non-responders). According to clinical data and serological tests, none of the dentists had presented disease or latent HBV infection during the eight years following the first vaccination. A 2 micrograms booster dose was administered intradermally to eight dentists with anti-HBs titers lower than 10 mIU/ml (non-responders) and to six dentists with titers ranging from 10 to 100 mIU/ml (poor responders); the determination of anti-HBs one month later demonstrated the occurrence of seroconversion in the eight non-responders and an increase in anti-HBs titer in the six poor responders. In summary, the present results demonstrated the prolonged persistence of protection against HBV infection and the development of immunologic memory provided by vaccination against HB--with intradermal application of three 2 micrograms doses of the Belgian recombinant vaccine at 0, 1, and 6 months--carried out eight years before in 51 dentists.