Horizontal or vertical transmission of hepatitis B virus? A serological survey in family members of hepatitis B carriers in Singapore.

Hepatitis B serology was performed on 270 family members of 78 hepatitis B carriers and hepatitis B e antigen status determined in those found to be HBsAg positive. The mean age of index patients was 38 years (range 3-74) and that of family members was 28 years (range 1-71). 67 family members (25%) were HBsAg positive. The proportions of family members positive for HBsAg and those negative for HBsAg but positive for anti-HBs and/or anti-HBc were 25% and 20% for children, 10% and 68% for spouses, 36% and 26% for siblings and 29% and 55% for parents. For children of index parents the proportions positive for HBsAg and those negative for HBsAg but positive for anti-HBs and/or anti-HBc were similar whether the index patient was the mother (24% and 24%) or the father (26% and 18%). Our results suggest that horizontal transmission is a significant mode of spread of hepatitis B within the family in Singapore.     

Changes in the anti-HBc profile of infants born to HBV infected mothers from Iran

From 2007 to 2014, 328 infants born to hepatitis B surface antigen (HBsAg) positive mothers, who received passive-active immunization against hepatitis B at birth were tested for HBsAg, antibody to hepatitis B core antigen (anti-HBc) and antibody to hepatitis B surface antigen (anti-HBs) at 12–15 months of age. Thirteen (4%) cases were HBsAg positive. Forty-four infants who were anti-HBs, anti-HBc positive (group 1) and twenty-one infants who were anti-HBc positive alone (group 2) were identified. Both groups were followed-up annually for testing anti-HBs and anti-HBc to verify if anti-HBc was of maternal origin. In group 1, anti-HBc disappeared in 41 cases at month 24, and it disappeared from the remaining 3 cases at month 36. In group 2, anti-HBc disappeared in 18 cases at month 24 and in the remaining 3 cases at month 36. The results show that maternal anti-HBc may persist up to 3 years in some children.     

Seroepidemiology of infection with hepatitis A virus and hepatitis B virus in the Seychelles

A batch of 417 serum samples obtained from native-born subjects were tested for the presence of hepatitis B surface antigen (HBsAg) and corresponding antibody (anti-HBs), by enzyme-linked immunosorbent assay (ELISA); and antibodies to hepatitis B core antigen (anti-HBc), e-antigen (anti-HBe), and hepatitis A virus (anti-HAV), by radioimmunoassay (RIA). HBsAg was found in only two of the 417 subjects studied. Anti-HBs was detected in 112 samples (26.8%), anti-HBc in 114 (27.3%) and anti-HBe in 31 samples (7.4%). Serologic evidence of a previous or present infection by hepatitis B virus (HBV) was found in 34.5% of the samples studied. Males showed a greater prevalence of anti-HBs and anti-HBc, while anti-HBe was more common in females; however, these differences were not significant. With regard to age, a significantly higher prevalence of anti-HBs (p less than 0.05), anti-HBc (p less than 0.025) and anti-HBe (p less than 0.025) was found in the older age groups. Anti-HAV antibodies were present in 90% of the subjects studied, with no variation between the sexes. The anti-HAV rate in the group under 20 years was similar to that found in the older age groups. The total infection rate of hepatitis B virus in the Seychelles is lower than in other tropical areas, HBs antigen/antibody ratio approaching that in temperate areas. Elucidation of the reasons for the low prevalence of hepatitis B virus carriers among the Sevchelles population requires further investigation.     

Epidemiological serosurvey of Hepatitis B in China—Declining HBV prevalence due to Hepatitis B vaccination

Objective

To determine the prevalence of hepatitis B surface antigen (HBsAg), hepatitis B surface antibody (anti-HBs), and hepatitis B core anti-body (anti-HBc) in a representative population in China 14 years after introduction of hepatitis B vaccination of infants.

Methods

National serosurvey, with participants selected by multi-stage random sampling. Demographics and hepatitis B vaccination history collected by questionnaire and review of vaccination records, and serum tested for HBsAg, antibody to anti-HBc and anti-HBs by ELISA.

Findings

The weighted prevalences of HBsAg, anti-HBs and anti-HBc for Chinese population aged 1–59 years were 7.2%, 50.1%, 34.1%, respectively. HBsAg prevalence was greatly diminished among those age <15 years compared to that found in the 1992 national serosurvey, and among children age <5 years was only 1.0% (90% reduction). Reduced HBsAg prevalence was strongly associated with vaccination among all age groups. HBsAg risk in adults was associated with male sex, Western region, and certain ethnic groups and occupations while risk in children included birth at home or smaller hospitals, older age, and certain ethnic groups (Zhuang and other).

Conclusions

China has already reached the national goal of reducing HBsAg prevalence to less than 1% among children under 5 years and has prevented an estimated 16–20 million HBV carriers through hepatitis B vaccination of infants. Immunization program should be further strengthened to reach those remaining at highest risk.     

Prevalence of hepatitis B, D and C virus infections among children and pregnant women in Moldova: additional evidence supporting the need for routine hepatitis B vaccination of infants

Rates of acute hepatitis B are high in Moldova, but the prevalence of chronic infection is unknown. In 1994, we surveyed children and pregnant women, collected demographic information, and drew blood for laboratory testing. Among the 439 children (mean age, 5 years), the prevalence of antibody to hepatitis B core antigen (anti-HBc) and hepatitis B surface antigen (HBsAg) were 17.1 and 6.8%, respectively. Among the 1098 pregnant women (mean age, 26 years), 52.4% were anti-HBc-positive and 9.7% were HBsAg-positive. Of the HBsAg-positive pregnant women, 35.6% were hepatitis B e antigen (HBeAg) positive and 18.3% had antibodies to hepatitis D virus. The prevalence of antibody to hepatitis C virus was 1.4% in children and 2.3% in pregnant women. The high HBeAg prevalence among HBsAg-positive pregnant women and the high anti-HBc prevalence among children indicate that both perinatal and early childhood transmission contribute to the high hepatitis B virus endemicity in Moldova.     

Prevalence and risk factors of hepatitis B in Spanish prostitutes

Eighty prostitutes were tested by solid-phase radioimmunoassay for serum markers of hepatitis B virus (HBV). Of 8 (10%) with hepatitis B surface antigen (HBsAg), 6 (75%) also had hepatitis Be antigen (HBeAg). Antibodies to HBsAg (anti-HBs) and to hepatitis B core antigen (anti-HBc) were found in 52 (65%). Antibodies to HBeAg (anti-HBe) were positive in 32 (40%). Anti-HBc alone was found in 5 (6%) and anti-HBs alone in 2 (2%). Sixty-seven (84%) were positive for at least one HBV marker and 13 (16%) were still susceptible to infection. Hepatitis B markers were more prevalent in prostitutes than in the normal Spanish population. Age, a history of sexually transmitted diseases (STD), drug abuse and promiscuity are factors which were highly related to hepatitis B markers. We concluded that screening prostitutes for the presence of markers and vaccinating those who are negative would be worth while.     

Universal immunization of infants with low doses of a low-cost,plasma-derived hepatitis B vaccine in South Africa

OBJECTIVE: To evaluate the effectiveness of universal vaccination against viral hepatitis B in South Africa among 18-month-old rural children. METHODS: Children were immunized with a course of low-dose (1.5 microg), plasma-derived hepatitis B vaccine at 6, 10 and 14 weeks of age, and blood samples from the children were tested for three hepatitis B markers: hepatitis B surface antigen (HBsAg), anti-HBs and anti-HBc. FINDINGS: One year after vaccination, a protective anti-HBs antibody titre of at least 10 IU/l was present in 669/769 (87.0%) of blood serum samples tested. Only 3/756 children (0.4%) were HBsAg positive and a fourth child was anti-HBc positive (HBsAg negative). This is a marked decrease compared to the hepatitis B prevalences reported in previous studies. Among rural migrant mine-workers, for example, HBsAg prevalence was 9.9%, and was 10.1% among children 0-6 years of age in the Eastern Cape Province. CONCLUSION: The low-dose, plasma-derived hepatitis B vaccine, which is affordable to most developing countries, was very successful in controlling endemic hepatitis B infection, where the virus is predominantly spread by horizontal transmission among infants and young children.     

Hepatitis B virus transmission in nursery schools

To determine whether transmission of hepatitis B virus occurs among children in nursery schools, from 1979 to 1982, 269 children (mean age 2.9 +/- 1.4 years) attending five nursery schools in which there were hepatitis B surface antigen (HBsAg) carrier children were tested for hepatitis B markers. Fifteen children (5.6%) were positive for HBsAg. Ten were possibly infected with hepatitis B in nursery school by HBsAg carrier children with hepatitis B e antigen (HBeAg). Four became HBsAg carriers and six developed transient antigenemia. Three other children were positive for the immunoglobulin M class of antibody to hepatitis B core antigen but negative for HBsAg. It is possible that they too were infected with hepatitis B in schools. These observations indicate that hepatitis B transmission most probably occurs among children in nursery schools in which there are HBsAg carriers with HBeAg, and therefore vaccination of susceptible children is necessary.     

深圳市居民乙型肝炎病毒感染危险因素分析

目的 了解广东省深圳市居民乙肝病毒(HBV)感染现状,分析HBV感染的相关危险因素.方法 于2010年在深圳市采用多阶段系统随机抽样方法抽取10个社区、1000户家庭,进行入户个案调查乙肝感染相关危险因素,并采集血样.用酶联免疫吸附试验(ELISA)检测乙肝血清标志物:乙肝表面抗原(HBsAg)、乙肝表面抗体(抗-HBs)和乙肝核心抗体(抗-HBc).结果 HBsAg、抗-HBs、抗-HBc阳性率和HBV感染率分别为6.68％ (252/3771)、71.92％(2 712/3771)、37.39％(1564/3771)和45.98％(1734/3771);≤15岁人群乙肝疫苗接种率为93.62％(1 752/1 872),＞15岁人群接种率为79.48％(1 509/1899),差异有统计学意义(x2=160.89,P ＜0.01);接种乙肝疫苗者与未接种者的HBV感染率分别为32.45％(1508/3261)和87.24％ (445/510),差异有统计学意义(x2 =552.72,P＜0.01);HBsAg阳性率与HBV感染率均随年龄上升有增加的趋势;多因素Logistic回归分析结果显示,家中有乙肝患者、内窥镜史、手术史及有偿献血史是深圳市居民乙肝感染的危险因素.结论 深圳市乙肝感染情况低于全国平均水平;乙肝感染具有家庭聚集性;医疗卫生因素对乙肝感染的影响较大.     

血源性乙肝疫苗远期免疫效果研究

[目的]通过评价新生儿血源性乙肝疫苗免疫后的远期保护效果,为进一步完善乙肝免疫预防策略提供依据。[方法]采用三层抽样方法,从上海市2个区1986-1996年出生的有全程血源性乙肝疫苗接种史的人群中抽取2692人作为调查对象,按免疫后不同时间分11个组,进行问卷调查,并采集静脉血进行乙肝表面抗体（anti—HBs）定量、乙肝表面抗原（HBsAg）与乙肝核心抗体（anti-HBc）检测。[结果]HBsAg阳性率平均为1．75％,未见随年龄增加而上升的趋势。anti—HBc阳性率平均为3．64％,呈随年龄增长而上升趋势。anti—HBs阳性率平均为40．16％;18岁以下青少年anti—HBs阳性率随年龄增长而下降,19岁以上者anti—HBs阳性率随年龄增长而上升。15～19岁组人群anti-HBs阴性率最高（66．80％）。多因素分析显示母亲孕期乙肝e抗原（HBeAg）阳性、家庭成员HBsAg阳性、男性、年龄增大是青少年感染乙肝的危险因素。[结论]血源性乙肝疫苗具有较持久的保护效果。建议开展15岁以上人群的定期随访,对anti—HBs阴性者需加强免疫。     

Nigerian medical students are at risk for hepatitis B infection

Medical students are exposed to blood and body fluids. This study was conducted to estimate the prevalence of hepatitis B virus (HBV) infection amongst medical students of the Lagos State University College of Medicine, Ikeja, Nigeria. Data were collected through a self-administered questionnaire and through blood analysis for hepatitis B surface antigen (HBsAg), hepatitis B 'e' antigen (HBeAg) as well as antibodies to the core (anti-HBc), surface (anti-HBs) and 'e' (anti-HBe) antigens. Three hundred and thirteen of 325 students (96%) participated. The mean age was 24.3+/-3.98 years; 231 (74%) were pre-clinical students and 82 (26%) were in the clinical years of study. Only 8 (2.6%) had received three doses of vaccination against HBV. Eighty-one (26%) tested positive for anti-HBc, 10 (3.2%) were positive for HBsAg and 56 (17.9%) had anti-HBs antibodies. A significant relationship was found between students who had a positive history of hepatitis B in the family and anti-HBc (P=0.03). Age was also significantly associated with HBsAg (P=0.012). Two hundred and twenty-five (72%) students were susceptible to the infection and required vaccination. Most students at this medical school are susceptible to HBV infection and should be vaccinated.     

Prevalence of immunologic markers of hepatitis A and B infection in hospital personnel in Miyazaki Prefecture, Japan

Between 1980 and 1983, a total of 1,883 serum samples from employees of four prefectural hospitals in Miyazaki prefecture, Japan were surveyed for antibody to hepatitis A virus (anti-HAV) and for the following hepatitis B virus markers: hepatitis B surface antigen (HBsAg), antibody to HBsAg (anti-HBs), and antibody to hepatitis B core antigen (anti-HBc). Overall prevalences were 36.9% for anti-HAV, 3.4% for HBsAg, 23.3% for anti-HBs, and 36.6% for anti-HBc. In the control group of 233 healthy persons, prevalences were 51.5% for anti-HAV, 3.0% for HBsAg, 28.3% for anti-HBs, and 33.5% for anti-HBc. No significant difference in the distribution of HBsAg was seen among five work categories. Anti-HBc prevalence was significantly higher in nurses than in office workers (p less than 0.05), other medical personnel (p less than 0.05), and controls (p less than 0.01). The differences between nurses and office workers and other medical personnel became greater with age, but a difference between nurses and the control group was recognized in every age group. A significant difference in the distribution of anti-HBc was seen between surgical physicians (36.7%) and nonsurgical physicians (27.1%). Prevalence of anti-HAV in physicians (32.8%), nurses (29.6%), and laboratory technicians (40.1%) was significantly lower than in the control group (51.5%). These data suggest that in the hospitals studied, hepatitis B is an occupational hazard to nurses and surgical physicians, but that hepatitis A is not.     

Prevention of perinatal transmission of hepatitis B virus: the sensitivity, specificity, and predictive value of the recommended screening questions to detect high-risk women in an obstetric population

The Advisory Committee on Immunization Practices recommends that all pregnant women be questioned concerning risk factors for hepatitis B virus infection and that those giving positive responses be serotested. The sensitivity, specificity, and predictive value of those recommended questions among 692 parturient women were determined. A total of 59 currently or previously infected women (hepatitis B surface antigen (HBsAg), antibody to hepatitis B surface antigen (anti-HBs), or antibody to hepatitis B core antigen (anti-HBc) seropositive) were compared with the 633 seronegative women. Among nonwhite women, the sensitivity of a positive response to any one of the recommended questions was 60%. Specificity and positive predictive value were 71% and 19%, respectively. Among white women, the sensitivity, specificity, and positive predictive value were 56%, 75%, and 11%, respectively. To increase such unacceptably low sensitivity, the authors included two additional questions: single marital status and Medicaid/medical assistance payer status. Sensitivity increased to 96% among nonwhite women and 84% among white women. However, a positive response to at least one of the recommended questions or to additional questions was elicited from 78% of all women (92% nonwhite and 64% white). The authors conclude that to prevent perinatal transmission of hepatitis B, we must serotest all women in our obstetric population.     

Transmission of hepatitis B virus among siblings

The authors investigated families with at least one hepatitis B surface antigen (HBsAg) carried in Okinawa, Japan, to determine possible routes of hepatitis B virus transmission within family units. A total of 175 members of 37 families on the western part of Iriomote Island, Okinawa, were followed up for 2-13 years; 68 were HBsAg-positive at least once. Sera were collected once a year. All serum samples were assayed by radioimmunoassay to determine presence of HBsAg, antibody to HBsAg (anti-HBs), hepatitis B e antigen (HBeAg), antibody to hepatitis B e antigen (anti-HBe) and antibody to hepatitis B core antigen (anti-HBc). In five of the 15 families with a positive mother and negative father, one or more HBsAg-positive children were found. In contrast, an HBsAg-positive child was found in only one of the eight families with a negative mother and positive father. In nine of the 14 families with both parents negative, two or more children were positive. Apparent sibling-to-sibling hepatitis B transmission occurred during the period of observation in four of the families with both parents negative. Eight children less than four years old were HBsAg-positive when first surveyed or became HBsAg carriers when four years of age or younger. No one over four years of age changed from HBsAg-negative to positive. This study found 1) in the family setting, there were cases of apparent maternal transmission but there were more cases of apparent sibling-sibling transmission, and 2) children under four years of age seemed to become carriers more easily than older children.     

Occupational risk of blood-borne viruses in healthcare workers: a 5-year surveillance program.

OBJECTIVE: This study presents the results of a 5-year surveillance program involving the prospective follow-up of healthcare workers (HCWs) in the Veneto region of Italy exposed to blood-borne viruses. DESIGN: All HCWs who reported an occupational exposure to blood-borne infection joined the surveillance program. Both HCWs and patients were tested for viral markers (hepatitis B surface antigen [HBsAg], antibody to hepatitis B surface antigen [anti-HBs], antibody to hepatitis B core antigen [anti-HBc], antibody to hepatitis C virus [anti-HCV], HCV RNA, and antibody to human immunodeficiency virus [HIV]) and had these markers plus transaminases assayed at 3, 6, and 12 months and then yearly thereafter. Moreover, a program of hepatitis B virus (HBV) prophylaxis was offered to those whose anti-HBs levels were less than 10 IU/mL. PARTICIPANTS: Two hundred forty-five HCWs (156 women and 89 men) with a mean age of 37 (+/- 10) years who reported occupational exposure during the 5-year period. RESULTS: At the time of exposure, 1 HCW was positive for HBsAg (0.4%) and 2 were positive for HCV RNA (0.8%). Among the patients involved, 28 (11.4%) were positive for HBsAg, 68 (27.8%) were positive for HCV RNA, 6 (2.4%) were positive for HIV, and 147 (60.0%) were negative for all viral markers (4 patients were positive for both HCV and HIV). During the follow-up period after exposure (mean, 2.7 [+/- 1.6] years), there was no increase in transaminases or seroconversions to any of the viral markers. CONCLUSION: Our accurate postexposure follow-up revealed a lack of transmission of HBV, HCV, and HIV.     

Marked decrease of hepatitis B virus infection among children in Okinawa, Japan

During the period 1980-1989 in Okinawa, Japan, serologic markers of hepatitis B infection (hepatitis B surface antigen; HBsAg, antibody to hepatitis B core antigen; anti-HBc) were investigated in nursery school children (1-4 years of age). Prevalences of HBsAg were 1.1-1.5% in the period from 1980-1984, but decreased to under 1.0% in the period from 1985. In 1989 there were two carriers in nursery schools, both born in 1985 or fathers who were HBsAg carriers. Prevalences of anti-HBc were 3.3-7.1% in the period from 1980-1983 with a decrease to 0.5% by 1988. Since hepatitis B vaccine was available for neonates whose mothers were HBsAg carriers with hepatitis Be antigen (HBeAg) and for nursery school children in 1983, hepatitis B virus infection among nursery school children and HBsAg carriers due to transmission from mother-to-child were markedly reduced. This strategy for immunization is useful in endemic areas. Immunization for children whose fathers are HBsAg carriers may also be necessary.     

Immunogenicity and safety of a plasma-derived heat-inactivated hepatitis B vaccine (CLB). Studies in volunteers at a low risk of infection with hepatitis B virus

The safety and immunogenicity of a plasma-derived heat-inactivated hepatitis B vaccine (CLB) were evaluated in 471 healthy human volunteers, who, both in their occupations and in their private lives, had been at minimal risk of being infected with hepatitis B virus. The first 202 individuals received three 3-micrograms doses of heat-inactivated hepatitis B surface antigen (HBsAg) at one-month intervals (trial A). A total of 42% one month after the first injection, 84% after two months, and 93% after five months had become anti-HBs (antibody to hepatitis B surface antigen) positive. In a second randomized study (trial B), the immunogenicity of five different dosages of the vaccine was compared in 269 volunteers. When the dose of HBsAg was diminished from 3 micrograms to 1.5, 0.6, and 0.25 microgram, no decrease of the anti-HBs response was observed. However, when the dose was diminished to 0.1 microgram of HBsAg, the anti-HBs response dropped significantly to 63% (p less than 0.001). In the recipients of all five vaccine dosages, no influence of sex and age was found on the anti-HBs conversion rates. During the eight-month observation period, none of the vaccinees became HBsAg and/or anti-HBc (antibody to hepatitis B core antigen) positive, and none developed antibodies associated with autoimmune liver disease. No serious side effects were observed.     

Infection by hepatitis B and C virus in non-intravenous drug using female prostitutes in Spain

We have studied the prevalence of hepatitis B (HBV) and hepatitis C virus (HCV) serologic markers in female blood donors and in female prostitutes and the relationship of antibodies to hepatitis B core antigen (anti-HBc) and of antibodies to HCV (anti-HCV) with the presence of treponemal antibodies (FTA-ABS) in non-intravenous drug using female prostitutes. Hepatitis B surface antigen (HBsAg) was found in 1.0% of the female blood donors, anti-HBc in 15.6% and anti-HCV in 0.7%. In the prostitutes, the prevalence of HBsAg was 6.1%, anti-HBc was positive in 29.0% and anti-HCV in 8.8%. No significant statistical association between the prevalence of anti-HBc or anti-HCV and the age of prostitutes (p = 0.9111 and p = 0.8254 respectively) or the length of time as prostitutes (p = 0.3583 and p = 0.5770) was found. FTA-ABS positive prostitutes had a significantly higher prevalence of anti-HCV than FTA-ABS negative prostitutes (p < 0.001). No statistical association was found between anti-HBc antibodies and positive FTA-ABS prostitutes (p = 0.336).Corresponding author.     

Seroepidemiology of hepatitis B virus infection among adults in Singapore: A 12-year review

We undertook a national hepatitis B seroprevalence study to assess the seroprevalence of hepatitis B virus (HBV) markers in the adult population in Singapore in 2010 and make comparisons with the seroprevalence in 1998 and 2004. The study involved residual sera from national health surveys conducted every six years since 1998. The tests for HBV markers were carried out using commercial chemiluminescent microparticle immunoassay. In 2010, the prevalence of hepatitis B surface antigen (HBsAg) among 3293 Singapore residents aged 18–79 years was 3.6% (95% confidence interval [CI] 2.9–4.2%). Hepatitis B e antigen (HBeAg) was detected in 4.2% of those who were HBsAg positive. About 22.5% (95% CI 21.1–23.9%) were positive for antibody to hepatitis B core antigen (anti-HBc). The overall population immunity to HBV, as determined by antibody to hepatitis B surface antigen (anti-HBs) ≥ 10 mIU/mL, was 43.9% (95% CI 42.2–45.6%). Among young adults below 30 years of age, HBsAg prevalence (1.1%) was half that in 1998 and 2004, and in those positive for HBsAg, none was positive for HBeAg in 2010, compared to 20.8% in 1998 and 15.8% in 2004. In this age group, anti-HBc prevalence also decreased significantly from 22.1% in 2004 to 4.4% in 2010, while anti-HBs (≥10 mIU/mL) prevalence increased significantly from 27.9% in 1998 to 43.3% in 2010 (p < 0.001). The national childhood HBV immunisation and catch-up programmes implemented in 1987 and 2001–2004, respectively, had a significant impact in reducing HBV infection and in raising the immunity of the adult population 18–29 years of age.     

Immune response to hepatitis B vaccine in parenteral drug abusers.

Responsiveness was assessed to a programme of vaccination of hepatitis B vaccine in a cohort of 197 intravenous drug addicts (mean age, 23.7 years) and their antibody response was compared with that of 271 healthy controls (mean age, 24.2 years). All participants were seronegative for hepatitis B surface antigen (HBsAg) and antibody to HBsAg (anti-HBs). The vaccination schedule consisted of three intramuscular injections (deltoid area) at months 0, 1 and 2. Although 70% of parenteral drug abusers received the three doses of vaccination, only 43.6% were evaluable for immune response. Fifty-eight per cent of heroin addicts and 80% of controls had evidence of anti-HBs seroconversion at 1 month after vaccination (chi 2 = 15.52, p less than 0.001). Geometric mean antibody titres were also significantly higher in controls (69.1 IU l-1; confidence interval 95%, 56.83 and 84.04) than in parenteral drug abusers (18.2 IU l-1; confidence interval 95%, 12.85 and 25.73) (F = 20.951, p less than 0.0001). The anti-HBs response was not influenced by coexistent anti-HBc, HCV antibody or HIV antibody seropositivity.