S. Riedemann

Facilitating the WHO Expanded Program of Immunization: the clinical profile of a combined diphtheria, tetanus, pertussis, hepatitis B and Haemophilus influenzae type b vaccine

BACKGROUND Vaccines are important weapons in the fight against infectious diseases. The World Health Organization (WHO) Expanded Program on Immunization (EPI) has been extended to include recommendations for hepatitis B and Haemophilus influenzae type b (Hib) vaccinations. The WHO has recommended that combined vaccines be used where possible, to reduce the logistic costs of vaccine delivery. This paper reviews the efficacy, safety and cost-effectiveness of Tritanrix-HB/Hib, the only commercially available combined diphtheria, tetanus, whole cell pertussis, hepatitis B and conjugated Hib vaccine. METHODS The immunogenicity and reactogenicity results of five published clinical trials involving Tritanrix-HB/Hib in a variety of immunization schedules and countries were reviewed. Based on these data and cost-effectiveness studies, an assessment of its suitability for use in national immunization programs was made. RESULTS Tritanrix-HB/Hib has shown excellent immunogenicity in clinical trials using a variety of schedules, with no reduced immunogenicity observed for any of the components of the combined vaccine. It has similar reactogenicity to DTPw vaccines alone. Pharmacoeconomic analyses have shown combined DTP-HB/Hib vaccines to be cost-effective compared to separate vaccines. CONCLUSIONS Replacement of DTPw vaccination by Tritanrix-HB/Hib can be done without modifying the existing national immunization programs. This should facilitate widespread coverage of hepatitis B and Hib vaccinations and their rapid incorporation into the EPI.

Seroprevalence of bovine viral diarrhea/mucosal disease in southern Chile

Abstract The seroprevalence of bovine viral diarrhea/mucosal disease (BVD/MD) was estimated using the serum neutralization technique on 948 cow serum samples collected from 40 large herds of the IXth and Xth Regions in southern Chile. In addition, 116 bulls were tested. The seroprevalence was found to be high, with 700 of the 948 cows testing positive (73.8%) at a titer of ⩾1:5. The herd seroprevalence was 100%, with all the herds studied containing at least one positive animal. The seroprevalence in bulls was 81.0%. The survey indicated a high seroprevalence throughout the study area, with a maximum of 87.4% in the province of Cautin, IXth Region. Furthermore, the prevalence of reactors was high in animals managed in extensive production systems and there were no differences in prevalence observed between beef, dairy and mixed farming. The results indicate that BVD/MD is widely distributed in the adult bovine population of large herds in southern Chile.

Immunogenicity and reactogenicity of combined versus separately administered DTPw-HBV and Hib vaccines given to healthy infants at 2, 4 and 6 months of age, with a booster at 18 months

OBJECTIVES To determine the immunogenicity and reactogenicity of a combined DTPw-HBV/Hib vaccine, in comparison with DTPw-HBV and Hib vaccines given as separate concomitant injections. METHODS In an open, randomized study, healthy infants were injected with either DTPw-HBV/Hib vaccine or separate DTPw-HBV and Hib vaccines at 2, 4 and 6 months of age, with a booster at 18 months. RESULTS Both vaccination regimens were immunogenic, with seropositivity rates of 100% after the booster vaccination for all vaccine components. Even as early as 2 months after the second dose of the primary vaccination, most patients had seroprotective antibody titers, the proportion of seropositive subjects approaching 100% for tetanus, hepatitis B, and Hib. Post-primary and post-booster geometric mean titers (GMTs) were well above seroprotective thresholds for each vaccine antigen in both groups, with no clinically relevant differences in the groups. The separate and combined administrations showed comparable reactogenicity profiles, and neither showed a significant increase in reactogenicity with successive doses. CONCLUSIONS The results of this study support the combination of Hib and DTPw-HBV vaccination in routine infant immunization at 2, 4 and 6 months of age with a booster at 18 months. Maximum benefit is obtained from compliance with the full course, but substantial benefit is likely to be achieved even in partially compliant patients, provided they receive at least two doses. Furthermore, these results demonstrate the tolerability of a fourth (booster) administration, where the addition of the Hib vaccine to DTPw-HBV did not lead to an increase in the overall reactogenicity.

Immunogenicity and reactogenicity of a combined hepatitis A and B vaccine in healthy Chilean subjects

OBJECTIVES A combination vaccine against hepatitis A and B provides the opportunity for simultaneous protection against both diseases with a single vaccine. This clinical study investigated the reactogenicity and immunogenicity of a combined hepatitis A and B vaccine (Twinrix, GlaxoSmithKline Biologicals, Rixensart, Belgium) in healthy Chilean adults between 18 and 40 years of age. METHODS In total, 345 healthy, seronegative health care workers were enrolled and randomized to three groups who received one of three lots of Twinrix on a 0-, 1- and 6-month schedules. Blood samples were screened 1 month after each dose for anti-HAV and anti-HBs antibodies. Reactogenicity after each dose was assessed using diary cards. RESULTS The nature and incidence of symptoms were similar to those reported for other Twinrix studies. Very few symptoms were scored as severe. Upon completion of the vaccination, all subjects had anti-HAV antibodies with titers

In vitro exposure of the early mouse embryo to Herpes Simplex Virus-1 strain Wal

6000 mIU/mL, and all but one were protected against hepatitis B, with titers

Accumulation and persistence of hepatitis A virus in mussels

4000 mIU/mL. CONCLUSIONS We have demonstrated the high immunogenicity and tolerance of the combined hepatitis A and B vaccine. Combined vaccination has the advantage of offering dual protection with a reduction in the number of injections needed, lower associated costs, and a positive impact on compliance.

Estudio serológico de Leucosis Enzoótica Bovina en un predio de la provincia de Valdivia y su relación a parámetros productivos y reproductivos

The causes of early embryonic death are not clearly understood, but one of them may be viral infection. To study the interaction between the virus and the undifierentiated cell, early mouse embryos in morula and blastocyst stages were exposed to Herpes Simplex Virus-1 WAL (HSV-1 WAL). In one group of a total of 167 embryos, 108 were exposed to HSV-1 WAL; the rest were maintained as controls. After washing in culture medium, these embryos were cultured on a murine fetal fibroblast monolayer for viral isolation. None showed cytopathic effects in the susceptible monolayer. In a second group, 140 empryos were exposed and 106 were maintained as controls. These embryos were cultured without a monolayer or washing to permit continuous viral contact. Eighty-seven of the exposed embryos and 74 control empryos developed normally 2 to 3 d post hatching with no morpnological differences between the two groups. No statistical differences were observed when the proportion of natched and degenerated embryos was compared. Our results indicated that the cells of early mouse embryos are not susceptible to HSV-1 WAL. We concluded that possibly the susceptibility of empryonic cells to viral agents partially depends on stage of differentiation.