Age-specific prevalence of hepatitis A antibody in Thai children

Age-specific prevalence of anti-HAV was determined for 3 groups of children whose mean ages were 12.6, 20.7 and 52.5 months. There were 41, 43 and 99 children in the respective age groups. All children were healthy, from middle to low socioeconomic families in Bangkok and vicinity. None of the children in the two younger age groups had anti-HAV antibody while 2 of 99 children in the oldest age group did. One of them resided in central Bangkok (Amphoe Dusit) and the other in Nonthaburi Province. The overall prevalence of anti-HAV in children under 5 years old was 1.1%. This demonstrates that hepatitis A transmission rates in Bangkok are very low when compared to ten years ago when prevalence rates were as high as 50-65%. From this study hepatitis A vaccine is recommended for 4-5 years old children in Bangkok. We need more epidemiologic data concerning hepatitis A transmission in Thailand before we can consider hepatitis A immunization for the whole country.

[Seroprevalence of anti-hepatitis A antibodies in Czech soldiers serving in U.N. forces--suggestions for a hepatitis A vaccination schedule]

Viral hepatitis A is a frequent disease particularly in developing countries. All workers and UN forces (UNO) are vaccinated against VHA with Havrix vaccine. The Czech units which were and are engaged on the territory of former Jugoslavia are not yet vaccinated against this contagious disease. The main purpose of the present study was to assess the immunity rate of VHA among Czech soldiers of the UN forces before their departure to the site of action. Another objective was to assess a suitable vaccination procedure. Sera were examined by the MEIA method (Microparticle Enzyme Immunoassay) in a fully automated IMx system in the Military Health Institute, Ceské Budĕjovice. For investigation HAVAB kits of Abbott Co. were used. A total of 667 serum samples were assembled, 19 had to be discarded because of small amounts (less than 50 microliters or because of haemolysis. The positive titre of "total" antibodies was set at 35 mIU anti-HAV; thus a total of 648 specimens were examined in 1991 - 1994 (1991 - 65, 1992 - 296, 1993 - 265, 1994 - 22). Of these 249 (38.4%) were positive and 399 (61.6%) were negative. The examined subjects were divided into four age groups (20 - 29, 30 - 39, 40 - 49, 50 - 59), the approximate distribution being 23%, 50%, 25%, 2%. The ratio of negative and positive specimens in different age groups was 1:0.3, 1:0.6, 1:1, 1:2.7. The seroprevalence of anti-HAV antibody increases from 25.3% in the first age group, in the second one it is 37.9%, in the third one 49.5% and 72.7% in the last age group, i.e. in the age bracket of 50 - 59 years. The results indicate a very low immunity rate in the lower age brackets and the necessity to vaccinate them before they depart. It is beyond doubt that it pays to examine the soldiers for the presence of total anti-HAV and immunize only subjects with a negative antibody titre. The vaccination approach Havrix 2 x 720 EU was recommended.

[Immunogenicity and tolerance of a combined hepatitis A/B vaccine. Preliminary results with a candidate vaccine]

AIM OF STUDY

Active immunization against hepatitis A having been undertaken in Germany since January 1993, a multicentre study was conducted to test, for the first time, immunogenicity of and tolerance to a candidate vaccine against hepatitis A and B.

SUBJECTS AND METHODS

50 healthy volunteers aged 18-40 years, negative for antibodies against hepatitis A (HAV) and B (HBs), received three intramuscular injections of the candidate vaccine (720 EIU of strain HM 175 and 20 micrograms recombinant HBsAg) in a total volume of 1 ml, on day 1 and then, one month and 6 months later.

RESULTS

Four weeks after the first injection the seroprotection rate (percentage of subjects with protective antibody titres) was 90% for HAV and 28% for HBs. The second injection produced seroconversion rates of 98% and 50%, respectively, and after the third one of 100% and 98%. All reported side effects were minor, of short duration and decreased after each injection. After the first injection, effects at the site of injection occurred in 50% of subjects, decreasing to 6% after the third one. The only systemic side effect, headache, occurred in only 4% of subjects and only after the first injection.

CONCLUSION

The test vaccine against hepatitis A and B proved to be highly immunogenic, safe and well tolerated.

Human T-lymphotropic virus type-I, and hepatitis A, B and C viruses in Nepal: a serological survey

In 1987, 676 blood samples were collected from inhabitants of the Bhadrakali and Kotyang villages in Nepal. The samples were tested for the prevalence of antibody to hepatitis A virus (anti-HAV), hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc), second-generation antibody to hepatitis C virus (anti-HCV) and antibody to human T-lymphotropic virus type-I (anti-HTLV-I). Anti-HAV was present in 99.3% of the people surveyed. The prevalence of anti-HAV reached 100% in the < 25 age group and was as high or only slightly lower in all other age groups. The prevalence of HBsAg was 0.3% and of anti-HBc 7.7%. Anti-HCV was found in 0.1% of the residents. No significant difference by gender or village was noted in the prevalence of anti-HAV, HBsAg, anti-HBc, or anti-HCV. No anti-HTLV-I-positive persons were identified. These data suggest that the prevalence of hepatitis B and C virus infections in Nepal is low in contrast to hepatitis A virus infection, and that human T-lymphotropic type-I infection may be absent in this population.

Safety and immunogenicity of an inactivated hepatitis A vaccine in children 2 to 5 years old

The reactogenicity and immunogenicity of an inactivated hepatitis A vaccine were assessed. Seventy healthy children aged between 2 and 5 years old, who lacked antibodies against the hepatitis A virus, were enrolled in this study. With a 0-, 1-, and 6-month vaccination schedule, the children received three doses of 360 enzyme-linked immunosorbent assay (ELISA) units of hepatitis A vaccine intramuscularly (deltoid). Safety parameters were recorded in standardized diary cards by the parents on the day of injection and the three following days. Blood tests for liver enzymes and anti-hepatitis A virus antibody analyses were performed the day of screening and 1, 2, 6 and 7 months after the first dose. Anti-hepatitis A virus antibody was tested by ELISA. Titres < 20 mIU/ml were considered negative. For the three hepatitis A vaccine doses administered, 22% (46/210) of the diary cards reported any kinds of signs or symptoms. Soreness at the injection site (9%, 18/210) and malaise (6%, 12/210) were the most common local and systemic reactions reported, respectively. The seroconversion rates were 83, 99 and 100% one month after the 1st, 2nd, and 3rd doses, respectively. The corresponding geometric mean titres were 124, 352, and 2,778 mIU/ml. We conclude that this HAV vaccine is safe and immunogenic in healthy children. As the hepatitis A epidemiology pattern is rapidly changing in our country (and other regions), resulting in an increasing population of susceptible adolescents and young adults, we suggest that the routine vaccination against hepatitis A in pre-school children attending day-care centres should be seriously considered.

Immunogenicity of an inactivated hepatitis A vaccine in healthy children: two years' follow-up

To investigate the long-term immunogenicity of an inactivated hepatitis A vaccine in children, 100 healthy children, aged between 1 and 7 years old and all lacking the antibody to hepatitis A (HA) virus, were enrolled in this trial. They received 3 doses of strain HM 175 HA vaccine with 360 enzyme-linked immunosorbent assay (ELISA) units at 0, 1 and 6 months, respectively. Blood sampling for antibody and aminotransferases was performed 7 days before, then 1, 6, 7, 12, and 24 months after the first dose. The titers of antibody to HA virus were tested by radioimmunoassay and ELISA methods. All subjects became ELISA seropositive at Month 6 after two doses of vaccine. Except for one boy, 99 remained seropositive at Month 24, with a geometric mean titer of 1,148 mIU/ml. Antibody titers for females were significantly higher than those for males throughout the follow-up period. It was concluded that the inactivated HA vaccine used in the present trial was immunogenic and safe in children below seven years old. The vaccine-induced antibody persisted for at least two years in 99% of the vaccinees.

An outbreak of hepatitis A among Irish haemophiliacs

BACKGROUND

An outbreak of hepatitis A (HAV) occurred in 1992 in Irish haemophilia A patients treated with high purity solvent-detergent (SD) treated factor VIII. Similar outbreaks were reported in Italy, Germany and Belgium. The aim of this study was to investigate the outbreak, and to test the hypothesis that it was caused by exposure to SD-treated factor VIII.

METHODS

A case-control study was started in early 1993. Haemophilia A cases with acute HAV (n = 29) were compared with haemophilia A controls for exposure to SD-treated factor VIII and other environmental factors. Details of factor VIII usage were obtained from the National Haemophilia Register and environmental data were obtained by a telephone-administered questionnaire. The response rate was approximately 90%.

RESULTS

The incidence of acute HAV infection among haemophilia A patients exceeded the notified national incidence of HAV by a factor of approximately 300. The incidence was higher in younger patients and those with more severe bleeding disorders. Contact with hepatitis, with children, and exposure to factor VIII were associated with increased risk. The association with factor VIII was the strongest risk factor after controlling for other factors (odds ratio = 27.6, 95% confidence interval [CI] 6.5-117.3). A dose-response effect was demonstrated.

CONCLUSIONS

Although person-to-person transmission is likely to have caused a few of the cases, the results of our investigation suggest that the major contributing factor was exposure to certain batches of SD-treated factor VIII.

Risk of hepatitis A in Dutch hemophilia patients

Recently, clotting factor preparations transmitted hepatitis A virus (HAV) to hemophilia patients. To study the risk of HAV infection in Dutch hemophilia patients, serum samples of 341 patients with hemophilia were tested for HAV antibodies (anti-HAV). 197/341 patients (group 1) were treated with clotting factor concentrates produced from large plasma pools, 144/341 patients (group 2) were treated with small pool cryoprecipitate. The test results were compared to those of healthy blood donors (n = 19,746) of the same age. In addition stored serum samples (1983-1994) from hemophilia patients were tested for HAV antibodies. No increased risk of HAV infection was found in Dutch hemophilia patients. The anti-HAV prevalence in group 1 was 20%, in group 2 13% and in blood donors 41%. A significantly (p < 0.002) lower percentage of HAV antibodies was found in hemophilia patients born in the 1950s using cryoprecipitate (11%) as compared to blood donors of the same age (40%), probably caused by passive administration of anti-HAV through clotting product. Passive immunization in the past was significantly (p < 0.02) more often found in group 2 (41.7%) than in group 1 (28%). In the period 1983 till 1988 five seroconversions were seen in group 1 (2%) and one in group 2 (0.7%). Anti-HAV seroconversions were not observed after 1988. In a risk analysis we estimated that 2 plasma pools of 10,000 Dutch blood donors per year may contain HAV. The absence of HAV among Dutch hemophilia patients suggests that this contamination is successfully inactivated.

[A relapsing and protracted form of viral hepatitis A: comparison of adults and children]

In recent years in children and adults with acute viral hepatitis A relapses and a protracted course of the disease were described. The authors followed up 37 patients with viral hepatitis A (20 children and 17 adults) and compared the clinical course of the disease, the period of hospitalization, persistence of IgM anti-HAV antibody in serum, the incidence of relapses and protracted forms of the disease. In adults the mean hospitalization period was longer (28 days as compared with 19), the average serum bilirubin value was higher (94 mumol/l as compared with 51 mumol/l), there were more cases with obvious jaundice (59% as compared with 30%) and the early serum antibody IgM anti-HAV persisted longer (19 weeks as compared with 14 weeks). Relapses of the disease were equally frequent (12% vs. 10%), however adults had more often a protracted course of hepatitis (23.5% vs. 10%). The observed differences were not statistically significant. Almost half the cases of hepatitis affected several members of the family. The results suggest that viral hepatitis A in adult age has a more severe course than in children. The authors recommend in cases with an elevated transaminase serum activity more frequent check-up examinations to avoid missing of a relapse, and to examine repeatedly IgM anti-HAV as in protracted forms of hepatitis IgM anti-HAV may persist even when the transaminase activity is normal.

Prevalence of hepatitis A antibody among disadvantaged gypsy children in northern Spain

The prevalence of antibody to hepatitis A virus (HAV) in a group of socially and economically disadvantaged Spanish gypsy children was compared to that of a group of non-gypsy middle-class children. The study included 438 children, 73 gypsies (38 girls and 35 boys, mean age 8.5 years, age range 2-16 years) and 365 non-gypsy controls, randomly selected by age. The presence of anti-HAV was investigated using ELISA. Among the gypsy children, 82% had antibodies to HAV compared with 9.3% of the children in the control group. The unfavourable living conditions of the gypsy population (e.g. homes with poor sanitary conditions, overcrowding) may explain the high prevalence of HAV infection. These findings underline the need for specific action which targets disadvantaged populations.

Need for vaccination of sewer workers against leptospirosis and hepatitis A

OBJECTIVES

This study compared the prevalence of Leptospira interrogans and hepatitis A virus (HAV) antibodies in serum samples from sewer workers and controls.

METHODS

A blood sample was obtained from 76 of the 101 municipal sewer workers (75%) of Quebec City and from two controls matched to each for age and sex. Testing was done for antibodies against serovars of Leptospira icterohaemorragiae, bratislava, hardjo, grippotyphosa, and kennewicki (pomona) and hepatitis A.

RESULTS

Sewer workers had a greater prevalence of antibodies against leptospirosis than controls (12% v 2%, P = 0.003). In contrast, antibodies to HAV were not significantly more prevalent among workers than among controls (54% v 49%, P = 0.51). Prevalence of HAV antibodies increased significantly with age both among workers and controls (chi 2 for trend, P < 0.001). In contrast with younger workers, prevalence of HAV antibodies was greater among workers > or = 40 years than among their controls (81% v 65%, P = 0.04).

CONCLUSION

Leptospirosis continues to be a problem to sewer workers but hepatitis A is apparently no longer a risk. The likely explanation is that leptospira are still abundant in the sewage system in contrast with HAV, which is only rarely to be found in sewage as a result of the generalised decrease in incidence of hepatitis A in the past three decades. The decision to vaccinate sewer workers against hepatitis A should take into account that it is impossible to avoid all contact with sewage fluid and, despite the fact that the actual incidence of hepatitis A is low, there is a real possibility of sporadic exposure during a future outbreak.

Anti-hepatitis A virus antibody response elicited in mice by different forms of a synthetic VP1 peptide

Peptide VP1 (11-25) of the capsid of hepatitis A virus was synthesized by the Fmoc-polyamide solid phase method, and administered to mice in different forms: (1) free, (2) encapsulated in multilamellar liposomes, (3) coupled to keyhole limpet hemocyanin (KHL), and (4) incorporated into a tetrameric branched lysine core. The highest anti-VP1 peptide responses were generated by synthetic peptides entrapped into liposomes and coupled to KLH. No anti-HAV response was generated with the free peptide, while all the other forms induced both anti-HAV and HAV-neutralizing antibodies. Maximum neutralization indices were observed in ascites from mice treated with liposome-entrapped and KLH peptides.

[Immunity against hepatitis A in younger age groups and the basis for an immunization program]

The naturally acquired immunity to hepatitis A virus (HAV) in a sample of 305 children, aged up to 15 years, in the municipality of Ivanić-Grad amounted to 18.7%. The study was conducted in September 1989. Of those 305 children, 16.8% of the boys and 20.7% of the girls were positive. No statistically significant difference was observed with regard to sex (p < 0.01) (chi 2 = 1.4). Of the children aged up to two years, 47.4% were exposed to the hepatitis A virus. Seropositive for anti-HAV were 8.3% in the group from 2-3 years of age, 6.4% in those aged from 4-5 years, 15.9% in the group from 6-7 years of age, 6.8% in those aged from 8-9 years, 20.0% in the group from 10-11 years of age, 27.8% in those aged from 12-13 years, and 29.0% in the group from 14-15 years of age. The spread of the infection by contact was predominant, reflecting the socioeconomic standards of the studied community (p < 0.01) (chi 2 = 29.5). A relatively high prevalence of hepatitis A infection compared to that of the developed countries, the first peak immunity rates in first-graders, a low number of cases among infants aged up to 5 years (approximately 6.0%), availability of commercial vaccine, speak in favour of including hepatitis A vaccination into the obligatory community-wide immunization program. It appears that the target age for HAV vaccination would be the age of five.

Patients with hepatitis A with negative IgM-HA antibody at early stages

Two patients with acute liver dysfunction who were negative for serum IgM-HA antibody on presentation became positive a week later. At early stages of hepatitis A, serum IgM-HA antibody may be negative. Another assay approximately 2 wk apart is recommended.

Antigenicity of hepatitis A virus after ultra-violet inactivation

Ultra-violet (UV) treatment has been shown to inactivate hepatitis A virus (HAV) in wastewater and polluted drinking water. Whether this method could be used to inactivate virus preparations made for vaccine purposes is not known since the effect of UV on the antigenicity of HAV has not been studied. HAV vaccine preparations have been treated effectively with formaldehyde. However, this method is time-consuming, since treatment times of up to 15 days have been published as necessary for a complete and safe inactivation. We used a cell-culture-derived HAV preparation with a TCID50 of 10(9) for a UV irradiation experiment. The antigenicity (assessed by a panel of anti-HAV antibodies), viral genome titre (quantitated by polymerase chain reaction) and HAV infectivity were compared after treatment with UV doses of 0, 184, 368, 552, 736 and 920 J m-2. Our results showed the antigenicity of HAV was almost unaltered even when infectious viral particles were no longer detectable. This technique shows potential as a simple and low-cost method for an inactivated HAV vaccine.

Immunogenicity and safety of an inactivated hepatitis A vaccine amongst Singaporeans

The immunogenicity and reactogenicity of an inactivated hepatitis A virus (HAV) vaccine was studied in healthy Singaporean adult volunteers. One hundred and forty healthy volunteers with normal alanine (ALT) and aspartate (AST) transaminases and no previous exposure to HAV, received three 1 ml doses (720 ELISA units) of an inactivated HAV vaccine (Smithkline Beechams Biologicals) following a 0, 1, 6 months vaccination schedule. All subjects were asked to record and grade the severity of any reactions for three consecutive days after each dose. Serum ALT and AST as well as anti-HAV were measured at 0, 1, 2, 6 and 7 months after the first vaccine dose. Anti-HAV seroconversion occurred when levels rose above 40 mIU/ml. Eighty-five percent of vaccinees seroconverted after the first innoculation and 99% after the second injection. All vaccinees seroconverted after the third dose. Geometric mean anti-HAV titers (GMTs) were, respectively, 119, 391, 4406 mIU/ml one month after each of the three doses. The most common side effect was transient pain and tenderness at the vaccination site. No elevation of ALT or AST levels were noted during the study period. The inactivated hepatitis A vaccine used in this study is safe and highly immunogenic in the local adult population. Two doses one month apart appeared to give adequate protection.

Prevalence of antibodies against hepatitis A virus among new immigrants in Israel

Israel, located in a region endemic for hepatitis A virus (HAV), recently absorbed a large population of immigrants who came from the former USSR. To assess the risk of high morbidity in this population a serosurvey of HAV antibodies was undertaken. Serum samples were collected from 965 new immigrants, of whom 664 came from the European, non-endemic region, and 301 from the Asian and Caucasian endemic regions of the former Soviet Union. They were compared to 240 Israelis. Each population was divided into six age groups: 1-9, 10-19, 20-29, 30-39, 40-49, and 50 years of age and older. The Asian/Caucasian immigrants and the Israeli population were found to share similar characteristics. In both groups, antibodies to HAV (anti-HAV) were present in the 1-9-year-old age group and reached maximum prevalence (90% and 86.7%, respectively) in the 20-29-year-old age group. In contrast, among the European immigrants anti-HAV was first found in the 10-19-year-olds and peaked (93%) in the age group of 50 years and older. It is concluded that immigrants originating from the European part of the former USSR may require vaccination against hepatitis A.

Efficacy of an inactivated hepatitis A vaccine in pre- and postexposure conditions in marmosets

A two-part challenge study was done in marmoset monkeys to confirm the efficacy of an inactivated hepatitis A vaccine. In part 1 (preexposure), 7 marmosets received a single low dose of vaccine (360 ELISA units [EL.U.]) and were challenged orally with wild type hepatitis A virus (HAV) either 1 or 6 months later. In part 2 (postexposure), 8 marmosets were challenged orally with HAV and then half each were inoculated with a single dose of 360 or 1440 EL.U. of vaccine 2 days later. The suboptimal immune response elicited by the low vaccine dose in the preexposure group was sufficient to induce complete protection against oral challenge with heterologous HAV in all marmosets that had responded serologically. In the postexposure group, the 360-EL.U. dose of vaccine resulted in partial protection against hepatitis A disease, whereas the 1440-EL.U. dose of vaccine elicited complete protection against disease and virus excretion.

Host immune response to hepatitis A virus

Hepatitis A virus (HAV) is transmitted by the fecal-oral route. The virus crosses through the gastrointestinal tract by an uncharacterized mechanism and travels to the liver, where it replicates in hepatocytes. It is released into the bloodstream and is simultaneously present in the bile and shed in the feces. Fecal shedding and viremia are maximal at the onset of liver function abnormalities and terminate about the time humoral immunity is detected, approximately 28 days after exposure. IgM, IgA, and IgG anti-HAV antibodies are usually present at onset of symptoms. Although the IgM response becomes undetectable usually within 6 months, IgG responses frequently persist for life, providing protection against reinfection. Pre- and postexposure immunization with pooled human serum immunoglobulin (ISG) is approximately 90% effective in preventing hepatitis A. Recipients of ISG have very low levels of detectable anti-HAV antibodies, and vaccines that elicit anti-HAV levels comparable with those produced by ISG should confer similar protection.

Clinical experience with an inactivated hepatitis A vaccine

Clinical trials of an inactivated hepatitis A vaccine have encompassed 104 studies completed by December 1993 in 27 countries. Studies involved 50,677 subjects and administration of > 120,000 vaccine doses. Results show that the vaccine is safe, clinically well-tolerated, and highly immunogenic in all age groups. A seroconversion rate of 100% is achieved 1 month after primary vaccination. Vaccine-induced antibody titers persist after a primary vaccination course for > or = 1 year with a single dose of 1440 ELISA units (EL.U.) in adults and after two doses of 360 EL.U. in children. A booster dose 6-12 months after the first vaccine dose induces very high antibody titers, which according to a mathematical model, are expected to protect against hepatitis A for > 20 years. The vaccine is equally immunogenic when administered simultaneously with other traveler vaccines, therefore enabling flexible and convenient vaccination against hepatitis A.