Safety and immunogenicity of an inactivated hepatitis A vaccine in preschool children

Young children in day care centers are an important source of hepatitis A virus (HAV) infection. The safety and immunogenicity of an inactivated HAV vaccine was evaluated in 57 children in day care centers. Nonimmune healthy children were given 0.5 mL of vaccine with subsequent doses: group A (28 children), second and third doses 1 and 2 months after the first; group B (29 children), second and third doses at 1 and 6 months. Antibody to HAV was measured before each dose and 8 months after the initial dose. All children developed antibody to HAV. Groups A and B had similar levels of antibody at 2 months; levels were lower in group B before the third dose and higher 8 months after the first dose. Local reactions after vaccination were reported in 17 children (29.8%). Minor systemic side effects that cleared spontaneously were observed in 27 children (47%).

Immunogenicity of an inactivated hepatitis A vaccine in Alaska Native children and Native and non-Native adults

The response to an inactivated hepatitis A vaccine was assessed in 307 persons: 163 Alaska Native children, ages 3-6 years, and 144 Native (84) and non-Native (60) adults. All adults received the same vaccine schedule (0, 1, and 12 months), whereas children were randomized to receive three different schedules (0, 1, and 6; 0, 1, and 2; or 0, 1, and 12 months). After one dose, 141 (96%) of 147 children and 129 (90%) of 143 adults responded with levels of antibody to hepatitis A virus > 20 mIU/mL. After three doses, all participants responded. The geometric mean titer (GMT) 1 month after the third dose was significantly higher in children who received the third dose 12 months after the first dose rather than 2 months after the first dose. While there were differences in the GMT of some blood samples by age, sex, and ethnicity, all participants responded to the vaccine.

Immunization of US soldiers with a two-dose primary series of inactivated hepatitis A vaccine: early immune response, persistence of antibody, and response to a third dose at 1 year

To study the feasibility of using inactivated hepatitis A vaccine for rapid immunization of US soldiers, 276 randomized seronegative volunteers received one of four regimens: two injections, on day 0 or one each on day 0 and 14, day 0 and 30, or day 0 and 180. A third dose was given on day 380. Among the 256 recipients of two doses, 99% responded with antibody (by ELISA) with few symptoms. A higher percentage of recipients of both doses on day 0 had antibody at day 14 (68% vs. 52% of all others, P < .03). The highest antibody concentrations (711 mIU/mL on day 240) were observed in subjects given a second dose on day 180. Recipients of the third injection developed a median 15-fold rise in antibody within 2 weeks. Virus-neutralizing antibody was detected in high titers after the third dose and neutralized strains of hepatitis A virus from several countries. Vaccines containing 1440 ELISA units of antigen may be useful for rapid immunization.

An outbreak of hepatitis A in school children at Nakhon Si Thammarat, southern Thailand

Hepatitis A antibody prevalence in Southeast Asia has markedly declined among children and adolescents. Therefore increasing a number of susceptible populations could result in an outbreak or epidemic. This paper reports an intensive study of an outbreak of hepatitis A in a primary school children during an endemic at Nakhon Si Thammarat, Southern Thailand. Eighty-nine children were inspected randomly from the total of 269 students, age ranged from 7-12 years old. The school children and parents were interviewed for their illness. Serological tests for antiHAV IgM and antiHAV (total antibody) were performed by ELISA. There were 36 cases of clinical acute hepatitis were positive for antiHAV IgM because of serological tests were performed nearly 4 months later. Seventy of 89 children tested were positive for antiHAV and 16 of them were positive for IgM class. Seven of 16 children with antiHAV IgM positive were asymptomatic. The significant risk factors for children with positive antiHAV were occurrence of hepatitis patients in the family and no latrine (p < 0.01). Endemic transmission in this outbreak occurred rapidly. Therefore preventive measures are essential in reducing the infection rate. In addition to personal hygiene, immunoprophylaxis with either immunoglobulin or HAV vaccine is recommended.

New epidemiological patterns of hepatitis A and B infections in Germany

A sero-prevalence study of antibodies against the hepatitis A and B virus is described along with the prevalence of the surface antigen of the hepatitis B virus (HBs1 Ag). Two groups are compared: the first comprising young adults born between 1961 and 1968; the second, an older population aged 50 and above. Results show that only 3.9% of the younger population were found to have antibodies against the hepatitis A virus, in sharp contrast to the older generation in whom the prevalence of antibodies was as high as 40.3%. There is a prevalence of 0.4% of HBs Ag in the younger group, while the rate in the older population is 1.5%. Only 7.1% of the younger group were found to have antibody markers for anti-HBc2 and 3.5% for anti-HBs. In the older group the respective figures are 32.5% and 15.8%.

History and epidemiology of hepatitis A virus

Hepatitis A was clearly recognized as an entity separate from other types of hepatitis during World War II, but only later did studies provide convincing evidence of the prevalence and transmission of hepatitis A virus (HAV). Disease incidence varies over time and geography, with wide differences from country to country and even within cities. Noted recently is a shift in prevalence in cases from childhood to adulthood. Incidence figures are unreliable. Epidemiology of the disease is best defined by measurement of anti-HAV antibodies. HAV is a very stable virus, frequently found in urban sewage. Infections occur early in life when sanitation is poor and living conditions crowded, but improvements in sanitation and hygiene have delayed infection, resulting in increasing numbers of adults susceptible to HAV. Transmission of HAV by blood is rare. High-risk persons include injection drug users, institutionalized persons and their caretakers, and those who travel from low-prevalence to high-prevalence countries.

Seroepidemiology of hepatitis A in the United States

The seroepidemiology of hepatitis A depends on the biologic features of the agent. Hepatitis A virus (HAV) is shed in the stool, and infectivity titers are significantly higher for stool than for other body materials. As a consequence, the predominant mode of spread is through fecal-oral routes. Common-source vectors include contaminated foods, water, and bivalve mollusks. Risk factors include contact with a person with hepatitis A, attendance or employment at a day care center, recent international travel, exposure to infected food or water during an outbreak, homosexual activity, and injecting drug use. No known risk factors are identified in many cases. Almost 40% of individuals in the United States are seropositive for prior HAV infection, and rates increase with age, perhaps reflecting an aging cohort of persons infected in earlier times when the infection was more common. Not unexpectedly, this decrease in current infection rates has increased the number of susceptible persons.

Inactivated hepatitis A vaccine: a safety and immunogenicity study in health professionals

The safety and immunogenicity of an inactivated hepatitis A vaccine (HM175) were evaluated in 151 seronegative health professionals (age range, 21-65 years; mean, 30). A 720-ELISA unit dose was administered to 78 vaccinees at 0, 1, and 6 months and to 73 vaccinees at 0, 1, and 12 months. Seroconversion rates were 90% in both groups 1 month after the first inoculation and 99% and 100%, respectively, 1 month after the second inoculation. Geometric mean antibody titers (GMTs) 1 month after the third inoculation were highest in the group vaccinated at 0, 1, and 12 months. GMTs were higher in women than in men. The vaccine was well tolerated; the most frequent side effect was transient soreness at the site of inoculation. No serious adverse reactions were observed. Thus, HM175 inactivated hepatitis A vaccine is safe and highly immunogenic.

Administration of hepatitis A vaccine to a military population by needle and jet injector and with hepatitis B vaccine

Military personnel are an important target population for hepatitis A immunization. Soldiers are often given vaccines by jet injector and may be required to receive multiple vaccines at one time. Formalin-inactivated hepatitis A vaccine containing 360 ELISA units of antigen was evaluated at Fort Campbell. Volunteers received vaccine at 0, 1, and 6 months as follows: group 1, hepatitis A vaccine by needle; group 2, hepatitis A vaccine by jet injector; group 3, hepatitis B vaccine by needle; and group 4, both hepatitis vaccines by needle in separate arms. Immune response and reactogenicity were evaluated. After two doses, recipients of vaccine administered by jet injector had a higher prevalence of antibody than those who received vaccine by needle (93% vs. 79%). By the 8th month, the vaccine was 100% immunogenic by either route or with hepatitis B vaccine. No interaction between hepatitis A and B vaccines was detected.

Development and retrospective evaluation of Hepaxpert-I: a routinely-used expert system for interpretive analysis of hepatitis A and B serologic findings

Hepaxpert-I is an expert system that interprets the results of routine serologic tests for infection with hepatitis A or B virus. The tests measure antibody to the hepatitis A virus (anti-HAV), IgM antibody to the hepatitis A virus (IgM anti-HAV), hepatitis A virus (HAV) in the stool, hepatitis B surface antigen (HBsAg) and antibody (anti-HBs), antibody to hepatitis B core antigen (anti-HBc and IgM anti-HBc), and hepatitis B envelope antigen (HBeAg) and antibody (anti-HBe). The knowledge base of Hepaxpert-I contains 13 If-Then rules for hepatitis A and 106 If-Then rules for hepatitis B serology. Formally, knowledge acquisition was done by forming a partition of each of the two sets of possible serologic finding patterns that contain patterns of serologic test results, 64 for hepatitis A and 4096 for hepatitis B, respectively. After entering an input pattern of serologic test results in Hepaxpert-I, a rule pattern matching algorithm based on indexing is internally employed as efficient access method for providing the respective interpretive text. Since 1 September 1989, Hepaxpert-I has been routinely applied at the Hepatitis Serology Laboratory of the 2nd Department of Gastroenterology and Hepatology at the University of Vienna Medical School (Vienna General Hospital). Beforehand, a retrospective evaluation of the expert system based on 23,368 hepatitis A and 24,071 hepatitis B serology requests was carried out.

Analysis of immunoassays to detect antibodies to hepatitis A virus (anti-HAV) and anti-HAV immunoglobulin M

Two newly developed anti-HAV tests were assessed, using a total of 1835 sera. These two tests are being distributed under the trademarks Enzymun-Test anti-HAV and Enzymun-Test IgM anti-HAV. The anti-HAV test was compared to anti-HAV tests from other manufacturers and featured a high sensitivity combined with a high level of reproducibility and specificity. In terms of sensitivity, reproducibility and specificity, the IgM test proved to be comparable to other IgM anti-HAV tests used for the diagnosis of acute type A hepatitis. Combining both tests was shown to be useful to recognize an acute or past hepatitis A virus infection. In addition, the high sensitivity of the anti-HAV test makes this test extremely useful to assess the immunoresponse to the hepatitis A vaccine.

Seroprevalence of antibodies against hepatitis A (anti-HAV) in Singapore: the NFDD experience

At the 4th National Foundation for Digestive Disease (NFDD) Day in 1991 where public lectures on prevention of hepatitis and early detection of hepatocellular carcinoma were given, screening of sera obtained from 364 registrants for antibodies to Hepatitis A (IgG) was undertaken. The overall sero-prevalence rate was 50%, with 55% for males and 46% for females with antibodies for HAV. None of the subjects below 20 years old had antibodies to HAV. This rose to 16% for those 21-30 years old and 92% for those above 61 years. This study shows that in Singapore, prevalence of anti-HAV antibodies rise with age and is approaching the low endemicity pattern that is seen in developed countries.

Age-specific prevalence of antibodies to hepatitis A and E viruses in Pune, India, 1982 and 1992

The age-specific seroprevalence of antibody to hepatitis A virus (HAV) and antibody to hepatitis E virus (HEV) were studied in persons in Pune, India, where both viruses are endemic. The data showed that HAV infected the majority of persons by age 3 years and virtually 100% by late childhood. In contrast, infection with HEV was rare in children and did not reach peak prevalence (33%-40%) until early adulthood. The reason for the differences in infection rates between HAV and HEV is not known. Age-specific antibody patterns in serum samples obtained 10 years apart show that neither HAV nor HEV has diminished in medical importance in this Indian community.

Serologic markers for hepatitis B virus and hepatitis A virus in Bushmen in West Caprivi, Namibia

A community based sero-epidemiological study was undertaken to determine the age specific prevalence rates of hepatitis A virus (HAV) and hepatitis B virus (HBV) infection in a band of Bushmen in the West Caprivi, Namibia. All children tested and all but two of the adults tested showed the presence of anti-HAV antibodies. Nineteen individuals (18%) were positive for HBsAg and 65 (61%) individuals had serologic evidence of past exposure to HBV infection.

Antibodies against hepatitis viruses in merchant seamen

Seamen constitute a special group of international travellers who may run an increased risk of contracting hepatitis, because of visits to foreign ports and the particular environment on board ship. The purpose of the survey was to assess the prevalence of serological markers for hepatitis A, B and C virus infection among seamen and to identify present and previous risk factors for infection. 515 seamen were studied. The prevalence of antibodies against hepatitis A was 0.3% in subjects below 40 years of age, increasing with age above 40 years, and highest among those who had sailed in international trade. The prevalence of antibodies against hepatitis B was 2.7% in subjects below 40 years of age, increasing to 35.7% in the group above 60 years of age. Hepatitis C antibodies occurred in 1.2%. Vaccination of sailors against hepatitis A should follow the same recommendations as to other travellers. The prevalence of hepatitis B was higher than in reference groups of non-seamen but, because hepatitis B is only one of many blood-borne diseases, prevention should be directed towards changes in behaviour rather than vaccination, except for special groups. Young seamen in international trade were found to be most at risk of contracting sexually transmitted diseases.

Hepatitis A antibodies in attenders of London Travel Clinics: cost-benefit of screening prior to hepatitis A immunisation

The seroprevalence of hepatitis A antibodies in travellers attending London Travel Clinics increases with age and screening may eliminate the need for vaccination at present for approximately 40% of adults. The duration of protection by current hepatitis A vaccine(s) is still to be established.

Immunogenicity and safety in adults of hepatitis A virus vaccine administered as a single dose with a booster 6 months later

An inactivated vaccine against hepatitis A was administered as a single 1,440 enzyme-linked immunosorbent assay (ELISA) units dose at month 0 with a booster at month 6 to 200 subjects divided into two age groups: group 1, 20-39 years (n = 134) and group II, 40-62 years (n = 66). At day 15, the seropositivity rates were 90% and 77% in groups I and II, respectively. At month 1 the seropositivity rate was 97% in both groups. At month 6 the seropositivity rates were 94% and 88% in groups I and II, respectively. One month after the booster, at month 7, 100% in both groups had become seropositive. The vaccine was well tolerated and did not cause any severe reactions. The results indicate that a single high vaccine dose offers protection against hepatitis A virus (HAV) for at least 6 months in the majority of cases where rapid vaccination is required even in travellers of older age. A booster dose will ensure long-term protection.

Inactivated hepatitis A vaccine: reactogenicity, immunogenicity, and long-term antibody persistence

This trial evaluated the reactogenicity, kinetics of antibody induction, and long-term immunogenicity of a 720 enzyme-linked immunosorbent assay units (EL.U.) antigen dose of an inactivated hepatitis A vaccine (Havrix, SmithKline Beecham Biologicals, Rixensart, Belgium). One hundred six healthy adult volunteers were enrolled to receive vaccine intramuscularly according to a 0, 1, and 6-month schedule. The vaccine was well tolerated. The most frequently reported local symptom was soreness, observed following 37.1% of all doses. Headache was the most frequently reported general symptom observed following 12.9% of documented vaccine doses. The administration of one vaccine dose induced seropositivity (anti-hepatitis A virus [HAV] > or = 20 mIU/ml) in 91% of all vaccinees 1 month later. The second vaccine dose resulted in seropositivity of the remaining vaccinees at month 2. All subjects remained seropositive for HAV antibodies at month 6, at which time the booster vaccine dose was given. At month 7, all vaccinees had anti-HAV titres > 200 mIU/ml. Serological results obtained at months 12, 18, 24, and 36 showed that antibodies against HAV induced by the vaccine booster dose persist for at least 30 months following its administration. All 49 subjects followed up until month 36 had antibody titres > or = 20 mIU/ml. The geometric mean titre (GMT) decreased by 60% from month 7 to month 12; between month 12 and 36, the GMT decreased by approximately 14% per period of 12 months. According to the vaccine-induced antibody kinetics and the magnitude of antibody level decrease over time, the predicted duration of antibody persistence is estimated to be at least 20 years.

Clinical and immunological investigation of a new combined hepatitis A and hepatitis B vaccine

As with hepatitis B vaccines, the recently developed hepatitis A vaccine is suitable not only for individual protection, but also for public health control measures. For introduction into routine immunisation programmes, however, hepatitis A vaccine should preferably be combined with other already established vaccines. In particular, a combination of hepatitis A and hepatitis B vaccines would be appropriate. We investigated a new combined hepatitis A/hepatitis B vaccine comparing its tolerability and immunogenicity with that obtained after separate or mixed simultaneous administration of the two components. Three groups of healthy volunteers, each of approximately 50 persons, were included. All were negative for hepatitis A and hepatitis B markers and had normal liver enzyme values. They received hepatitis A (720 ELISA units) and hepatitis B (20 micrograms) vaccines in the deltoid muscle, combined, mixed or separately, according to a 0, 1, 6-month schedule. Blood samples for determination of antibodies to hepatitis A virus (anti-HAV) and hepatitis B virus (anti-HBs) and of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were drawn at months 0, 1, 2, 6, and 7. Local and systemic reactions were monitored by means of questionnaires. The results of our study demonstrate that the combined hepatitis A and B vaccine is well tolerated and highly immunogenic. The seropositivity and seroprotection rates were 100% for both antigens in all groups. Surprisingly, anti-HAV and anti-HBs antibody titres after the combined and mixed vaccines were significantly higher compared with the respective monovalent vaccines injected separately.

Exposure to enteroviruses and hepatitis A virus among divers in environmental waters in France, first biological and serological survey of a controlled cohort

An epidemiological study of hepatitis A and enteroviruses was conducted in a military diving training school, by evaluating the viral contamination of water using an ultrafiltration concentration technique, and assessing seroconversion and the presence of virus in stool specimens obtained from 109 divers and 48 controls. Three of 29 water specimens were positive for enterovirus by cell culture and 9 by molecular hybridization. There was little or no risk of virus infection during the training course (49 h exposure) because there was no significant difference between divers and controls for both viral isolation and seroconversion. However, a higher percentage of coxsackievirus B4 and B5 seropositive divers suggests that these were more exposed during previous water training. No hepatitis A virus (HAV) detection and no seroconversion to HAV was observed. The rate of HAV seropositive subjects was 17% in this 24.5-year-old population.

Single dose inactivated hepatitis A vaccine: rationale and clinical assessment of the safety and immunogenicity

In comparison with the classical immunisation schedules (0-1-6 or 0-1-12 months) for hepatitis A, a 0- and 12- or a 0- and 6-month schedule would have important advantages by reducing the number of injections and discomfort and increasing scheduling convenience and patient compliance. It would be convenient if a single dose with enough antigen could protect both rapidly and for at least 12 months, when the booster dose would be given. Several clinical trials have been carried out with an inactivated hepatitis A vaccine containing 1,440 EL.U. (1 ml), according to a 0-12 and a 0-6 vaccination schedule. This hepatitis A vaccine is safe and well tolerated. It offers a rapid seroresponse: 14 days after a single dose the seroconversion is 88% (95% C.I.: 84.6-90.9). The 0-12 schedule study showed good persistence of hepatitis A virus (HAV) antibodies with a seroconversion rate of almost 95% at month 12. Booster doses given at 6 or 12 months result in a substantial rise in antibody levels; according to these antibody titres, the 1,440 EL.U. vaccine can be expected to confer comparable duration of protection as the 720 EL.U. vaccine, i.e., 10-20 years. Preliminary data show that timing of the booster may not be critical for the antibody response. In conclusion, the 1,440 EL.U. hepatitis A vaccine is safe, offers rapid seroconversion, and is highly immunogenic. The persistence of HAV antibodies until month 12 allows a certain flexibility in the administration of the booster: month 6 or 12, and a 0-12 or 0-6 schedule can increase the vaccination compliance.

[Immunogenicity and stability of an aluminum-free liposomal hepatitis A vaccine (Epaxal Berna)]

The high immunogenicity of the liposomal hepatitis A vaccine (Epaxal Berna) after a single dose and after a booster dose one year later has been confirmed in several studies with healthy adult volunteers: 95-100% and 96-100% seroconversion (> or = 20 mIE/ml) after 1 and 12 months respectively, as well as a booster effect in 100% of the cases after revaccination. The tolerability of this new, alum-free vaccine has been excellent with 6-25% local and 0-13% mild systemic reactions after a dose of 0.5 ml. Stability testing with and without detergent indicated partial internalization of the hepatitis A virions in the phospholipid bilayer of the liposome vesicles with storage. Immunization of 10 healthy adult volunteers with vaccine stored for 32 months at 4 degrees C showed, however, that the duration of storage has no influence on immunogenicity and tolerability of the vaccine.