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

Cell mediated and antibody immune response to inactivated hepatitis A vaccine

The humoral and cellular immune response to inactivated hepatitis A vaccine was investigated dynamically in a time elapse study over 1 year. Fourty-five healthy volunteers, seronegative for anti-HAV, were vaccinated with 1440 enzyme-linked immunosorbent assay units (EU) of formalin-inactivated hepatitis A virus following a 0--6-month schedule. Serum anti-HAV levels and HAV-specific proliferation of peripheral blood mononuclear cells were measured at several time points over a 26- and 28-week period after the first and second injection, respectively. Distinct B and T cell responses were determined within 14 days after primary vaccination. The booster vaccination-induced immediate peak levels for the humoral (anti-HAV GMC=5376mIU/ml) as well as the cellular (median Deltacpm=14173cpm) response.

[Research activity on pediatric vaccines in Spain: descriptive analysis of prospective studies published between 1990 and 1998]

OBJECTIVE

To describe the overall characteristics of prospective studies on vaccines in children, performed by Spanish investigators and published between 1990 and 1998.

METHODS

Through a bibliographic research on MEDLINE and EMBASE, 24 prospective studies, performed in Spain, published as original papers, and with objectives directly related to the administration of vaccines to children have been identified. These studies were grouped as: clinical trials (group A), studies performed on established vaccination programmes (group B), and those that could not be included in the above mentioned groups (group C).

RESULTS

5, 9 and 10 studies belonged to groups A, B and C, respectively. More than 12,800 subjects participated in these studies, belonging to both normal population or specific risk groups. In 11 studies, the study population comprised newborns and infants. The vaccines under investigation were: hepatitis B (10 studies), DTPe/Pa (6), MMR (3), flu (2), Hib (1), hepatitis A (1), and meningococcus A and C (1) to address different objectives (in most of them, immunogenicity and/or reactogenicity). Nine had external financial support; 21 were performed by hospital and/or primary care investigators, and 18 in the Vasque Coutry, Madrid or Valencia. 13 publications reported obtaining informed consent, and 8 on the approval of the study protocol by an independent committee. Ten studies were published by international journals.

CONCLUSIONS

This study shows that most of the studies are conducted by clinicians, with vaccines targetted to newborns and infants, with no external financial support, in a small number of autonomous communities, and usually published in Spanish Journals. The submission of this type of studies to a research ethics committee is desirable, something done to a lesser extent than obtaining informed consent.

Safety, immunogenicity and antibody persistence of an inactivated hepatitis A vaccine in 4 to 15 year old children

Among 277 healthy Venezuelan children, aged between 4 and 15 years, who were screened for hepatitis A virus (HAV) antibodies, 118 seronegative children were enrolled in an open study. Each child received one dose of the Pasteur Mérieux Connaught inactivated hepatitis A vaccine (AVAXIM¿trade mark omitted¿, 160 antigen units), followed by a booster dose 24 weeks later. All seronegative subjects seroconverted 2 weeks after immunisation (antibody titres greater, similar20 mIU/ml), and antibody titres were still over greater, similar20 mIU/ml after 24 weeks, at the moment of the booster dose. The anti-HAV antibody geometric mean titre (GMT), as measured by a modified radio-immunoassay (HAVAB(R), Abbott Laboratories, North Chicago, IL, USA), was 73.7 mIU/ml, 2 weeks after the first dose. Four weeks after the booster, the GMT value reached 6999 mIU/ml, representing a 29.6-fold rise from pre-booster levels. One year after the booster dose, the GMT value was 1673 mIU/ml in the 92 subjects who provided blood samples at this time, all of whom were still seroconverted ( greater, similar20 mIU/ml). No serious adverse event related to the vaccination occurred during the study. No immediate systemic reaction occurred. Local reactions were reported by 9.3% of subjects who received the primary injection and 5.5% of those given the booster dose. The systemic reactions were mainly fever and myalgia reported over the 7 days following the injection by 3.4% of subjects after the first dose and 5.5% of subjects after the booster dose. A clinically significant elevation of serum transaminase from pre-immunisation levels was noted in one subject (AST level 2.2 times the upper normal limit) 2 weeks after the first injection, although this was not associated with any clinical signs of impaired liver function. This trial demonstrated that AVAXIM¿trade mark omitted¿ containing 160 antigen units is safe and highly immunogenic in healthy children aged between 4 and 15 years, and could be included in the childhood vaccination schedule to control infection in areas endemic for hepatitis A.

Prevalence of hepatitis A virus among Saudi Arabian children: A community-based study

HAV is endemic in Saudi Arabia, with about 90% of the adult population having positive anti-HAV. A population-based survey of hepatitis B virus markers provided an opportunity to determine the age-related prevalence of anti-HAV among Saudi children and examine some of the factors that influence its transmission in the community. The overall prevalence of anti-HAV is 52.4% of 4375 children tested. There was no significant difference in HAV prevalence between males and females (51.3% vs 53.5%). The age-specific rates, which were similar in both sexes, indicated the lowest rate in infants with a steady increase in the older age group. There was a marked regional variation in anti-HAV prevalence, the Eastern region showing the lowest prevalence (38.4%), while the Northwestern region showed the highest prevalence (67%). In nearly all the regions, rural inhabitants had a higher prevalence than urban residents. Socioeconomic factors had a significant correlation with the prevalence of anti-HAV, with the level of education of parents having the strongest influence on HAV prevalence. The high overall HAV prevalence in children confirms that Saudi Arabia is endemic for HAV infection, despite the recent improvement in the socioeconomic standards of its population. The pattern of HAV may be changing in Saudi Arabia as the prevalence has dropped in the Central province compared to previous reports. The need for the introduction of hepatitis A vaccination will be determined in the future definition of HAV epidemiology in Saudi Arabia.