Hepatitis A vaccination: schedule for accelerated immunization

Hepatitis A virus infections, immunisations and demographic determinants in children and adolescents, Germany

Hepatitis A is a vaccine-preventable disease with a global distribution. It predominantly occurs in regions with inadequate living conditions, but also affects populations in industrialised countries. Children are frequently involved in the transmission of hepatitis A virus (HAV) and thus play a central role in the epidemiology of hepatitis A. Here, we investigated HAV infections, immunisations, and associated demographic determinants in a nationwide, population-based, cross-sectional survey conducted in Germany from 2003-2006. Out of 17,640 children and adolescents, complete data sets (HAV serology, demographic information and vaccination card) were available for 12,249 (69%), all aged 3-17 years. We found protective antibody levels (>=20 IU/L) in 1,755 (14%) individuals, 1,395 (11%) were vaccinated against hepatitis A, 360 (3%) individuals were HAV seropositive without prior hepatitis A vaccination, thus indicating a previous HAV infection. Antibody prevalence (attributable to vaccination or infection) increased significantly with age. Multivariate logistic regression revealed that predominantly children and adolescents with migration background-even if they were born in Germany-are affected by HAV infections. Our results provide a rationale to emphasise existing vaccination recommendations and, moreover, to consider additional groups with a higher risk of infection for targeted vaccination, especially children with a migration background.

Hepatitis A control in a refugee camp by active immunization

An outbreak of hepatitis A occurred among children of a refugee camp in Croatia. In order to disrupt the outbreak, we decided to vaccinate children from 1 to 15 years of age in the camp, in addition to intensified general preventive measures. Assuming high prevalence of hepatitis A virus antibodies within this population, we conducted anti-HAV testing of the children eligible for vaccination. Of 108 children tested, 74 (68.5%) were anti-HAV positive. We vaccinated 34 children. One month after vaccination 31 previously negative children were tested for anti-HAV and 30 of them were found positive, suggesting a seroconversion rate of 96.8%. One child fell ill 5 days after vaccination, after whom no new cases of hepatitis A occurred. Thus we conclude that active immunization is a successful means of stopping an outbreak of hepatitis A.

Immune globulin and vaccine therapy to prevent hepatitis A infection

The hepatitis A virus is usually transmitted person-to-person due to fecal-oral exchange of virus. Approximately 30,000 infections are reported each year in the United States, with the actual incidence being much greater. Prophylaxis with immune globulin has had a minimal impact on the overall incidence of hepatitis A. The recent availability and proven efficacy of a hepatitis A vaccine offers the hope that the incidence of infection may be substantially reduced. Pre- and postexposure prophylaxis should be targeted to individuals at increased risk of either acquiring infection, transmitting infection, or developing fulminant hepatitis, or to help control epidemics. This article reviews the current literature and discusses recommendations for pre- and postexposure prophylaxis against hepatitis A virus.

Immunogenicity of an inactivated hepatitis A vaccine in Dutch United Nations troops

Limited information existed on the immunogenicity of an inactivated hepatitis A vaccine as part of an extensive vaccination schedule. Dutch marines bound for duty in Cambodia received inactivated hepatitis A vaccine (720 ELISA units of antigen, two intra-gluteal doses at a 2-week interval before departure and an intra-deltoid booster vaccination after 8 months) simultaneously with several other vaccines. Hepatitis A antibodies were determined in blood-samples drawn before and after the booster vaccination, using two laboratory tests (modified HAVAB and SBB-ELISA). At 8 months, before the booster vaccination, 52% (modified HAVAB) and 81% (SBB-ELISA) had seroconverted. Risk factors for non-seroconversion were increasing age and a typhoid vaccination. At 11 months 97.6% (modified HAVAB) and 100% (SBB-ELISA) had seroconverted. Non-seroconversion at 8 months was remarkably high. SBB-ELISA was more sensitive in lower titre ranges.

An outbreak of hepatitis A in a French day-care center and efforts to combat it

An outbreak of hepatitis A in a French day-care center was identified during a survey of risk factors for such events in a sample of 210 centers. In the period between 29 March and 9 July 1994, 17 cases were diagnosed in the center (anti-HAV IgM serum antibody) including 11 children aged 2-3 (attack rate = 55.5% of class), 2 staff members, 3 parents and 1 educator-parent (secondary attack rate = 27.6%). The source case was probably a classmate of Case 1's older brother, who was diagnosed earlier in the spring. Intensive hygiene measures and the organisational features of the clinic limited all transmission except by direct physical contact with infected children. Vaccination of staff was begun too late to be effective; gamma-globulin prophylaxis might have been administered but was not. This is the first documented outbreak of the disease in a French center.

Development of a single-shot subunit vaccine for HIV-1. 3. Effect of adjuvant and immunization schedule on the duration of the humoral immune response to recombinant MN gp120

HIV-1 prophylaxis may require "sterilizing immunity" (i.e., the prevention of infection), and this is likely to demand a vaccine that gives high, long-lasting antibody titers. Although it is known that vaccine adjuvants and immunization schedule affect the magnitude of the immune response, there are few reports on antibody decay rates and persistence. Guinea pigs were immunized with recombinant gp120 using different adjuvants and immunization schedules, and the anti-gp120 and HIV-1 neutralization titers were determined over time following the last booster immunization. As observed previously in the literature, a longer time between boosting gave higher titers, with a slight increase in the decay half-life as the booster was spaced farther out from the primary immunization. The decay rate of the antibody titers showed surprisingly little effect of adjuvant, except for sustained-release polymer-based formulations. Adjuvants that gave high titers initially after boosting showed the greatest persistence of antibody titers (persistence defined as the residual titers at long times). These data show that high, long-lasting titers may be achieved by using sustained-release formulations, and these are likely the prime vaccine candidates for prophylaxis requiring prolonged sterilizing immunity.

Immunogenicity of an inactivated hepatitis A vaccine administered according to two different schedules and the interference of other "travellers" vaccines with the immune response

A total of 2036 persons consulting vaccination centers in Germany were vaccinated with an inactivated hepatitis A vaccine (containing 720 ELISA units of antigen) either according to the standard schedule (two vaccinations given 4 weeks apart) or to an abbreviated schedule (two vaccinations given 2 weeks apart) in a controlled clinical study. The abbreviated schedule induced a similar rate of seroconversion and geometric mean antibody titre as compared to the standard schedule. The incidence of reactions reported after vaccination was similar in both groups. When other "travellers" vaccines were given simultaneously neither the immunogenicity nor the reactogenicity of the hepatitis A vaccine were influenced. These findings have considerable practical importance in the prevention of hepatitis A in travellers.

Safety and immunogenicity of hepatitis A vaccine in healthy adult volunteers

The immunogenicity and adverse reaction of an inactivated hepatitis A (HA) vaccine were investigated. Sixty healthy adult volunteers who lacked antibody to HA virus (anti-HAV) received three doses of vaccine containing 720 enzyme-linked immunosorbent assay (ELISA) units (EL.U) according to a 0, 1 and 6 month schedule. Blood tests for serum liver enzymes and anti-HAV were performed at screening 7 days prior to, and 1, 6 and 7 months after the first dose. Anti-HAV was tested by radio immunoassay and ELISA for titre determination. The seroconversion rates measured by ELISA were 98.3% (59/60) at months 1 and 6 and 100% at month 7. Sixty-one per cent (109/180) of the documented injections were followed by local symptoms, essentially mild soreness at the site of injection; and 22.2% (40/180) by minor general symptoms including malaise, fatigue and lethargy. It is concluded that HA vaccine is highly immunogenic and safe. It may replace immunoglobulin as an effective method of preventing HA virus infection in adults.

Field evaluation of a hepatitis A vaccine in a Norwegian contingent to the United Nations Interim Force in Lebanon

The Norwegian population is basically seronegative regarding anti-hepatitis A antibodies. For this reason they are particularly vulnerable when exposed to hepatitis A virus when staying in highly endemic areas. Norwegian UN-personnel have so far been protected with serum immunoglobulins (Ig). Two studies are reported, one followed a vaccination schedule of 0, 1 and 2 months with a booster at month 12, while the other followed a schedule of day 0 and 14 with a booster at month 7. Both were field trials evaluating the new hepatitis A vaccine, from SmithKline Beecham Biological, in Norwegian UN soldiers serving in Lebanon. Both trials showed 100% seroconversion following the initial vaccination course, with low reactogenicity and no clinical or subclinical sign of hepatitis. The new vaccine has decisive advantages over immunoglobulins on medical, practical and economic grounds.

Clinical assessment of the safety and efficacy of an inactivated hepatitis A vaccine: rationale and summary of findings

The objectives for the clinical testing of the inactivated hepatitis A vaccine developed by SmithKline Beecham Biologicals are reviewed and the results obtained are summarized. The first studies were carried out in healthy young adult volunteers using pilot vaccine lots prepared from the CLF and HM175 strains of hepatitis A virus (HAV). It was established that the candidate vaccines were well-tolerated, caused no hypersensitivity reactions and elicited a strong antibody response. As the yield in production with the HM175 strain was higher it was preferred over the CLF strain for further development of a vaccine. A dose-range study with HM175 vaccine in adults showed that an antigen dose of 720 ELISA units (El.U) produced almost 100% seroconversion after one injection. This dose was therefore chosen as appropriate for adults. A dose of 360 El.U was used in children. To date, a total of 67 studies in 18 countries involving 47,145 subjects, including 20,586 control subjects, have been initiated. In these studies, 55,259 doses of HM175-derived hepatitis A vaccine have so far been administered. This extensive experience has shown that the vaccine is well-tolerated, causing essentially only mild, transient local reactions. Vaccine reactogenicity was assessed using symptom checklists, filled in by the volunteers or their parents, for a period of 4 days following vaccination. Blood samples were obtained at different times after vaccination to evaluate the immune response. Clinical studies with six different lots, manufactured using commercial-scale production methods, have been carried out on 2901 adults. These studies have shown that a seroconversion rate of 95.7% (1225/1280) is obtained one month after the first vaccine dose.(ABSTRACT TRUNCATED AT 250 WORDS)