Immunogenicity of Haemophilus influenzae type b polysaccharide--diphtheria toxoid conjugate vaccine in adults

The capsular polysaccharide of Haemophilus influenzae type b is a poor immunogen in human infants. In an attempt to enhance immunogenicity, this polysaccharide was covalently coupled to diphtheria toxoid and the conjugate tested as a vaccine in adult volunteers. Two injections of PRP-D vaccine were given, separated by one month. The anti-PRP antibody responses in this group were compared with those in a group receiving a comparable dose (20 micrograms) of conventional PRP vaccine. Both vaccines were well tolerated. A single injection of PRP-D was significantly more immunogenic than PRP, eliciting higher serum concentrations of total anti-PRP antibody 1 month later (geo means of 248 and 62 micrograms/ml, respectively; P less than 0.001). In addition, higher concentrations of IgG anti-PRP antibody were observed in the PRP-D group (P less than 0.001). One month after reinjection of vaccine, subjects receiving PRP-D showed a small but significant decline in total antibody (P = 0.03), whereas the serum antibody concentrations in the group that received PRP remained unchanged. At 12 months, the antibody concentrations of the two groups were not significantly different. Bactericidal activity and passive protection activity (infant rat model) were tested in pooled sera from the three highest and three lowest responders in each vaccine group; both PRP and PRP-D vaccines induced biologically active anti-PRP antibody. Thus PRP-D was found to elicit biologically active serum antibody and to be more immunogenic in adults than PRP vaccine; however, the duration of higher concentrations of antibody was transient.

[Status and tasks of goal-oriented planning of research with regard to the problem of diphtheria]

The work deals with the prospects of scientific research in the prophylaxis of diphtheria. The authors consider the necessity of creating the complex goal-oriented program of scientific research, such program being the basis of forward planning.

Diphtheria immunity in Massachusetts--a study of three urban patient populations

To determine the status of diphtheria immunity among our patients, we measured diphtheria antitoxin levels in three separate patient populations. The technique used was toxin neutralization in rabbit skin, which allowed us to evaluate the immune status of individual patients. We studied an emergency room population, a sampling of inpatients from an urban teaching hospital, and a group of older patients from a chronic care hospital. Overall, approximately 80% of patients had adequate diphtheria antitoxin levels in their serum. However, two subgroups emerged with lower levels, with potential nonimmunity. These were certain young patients, either foreign born or with a potentially "immunocompromising disorder," and the elderly chronically ill. We conclude that while overall diphtheria immunity in our patients appears adequate, subgroups with increased risks do exist and immunization for these subgroups should be undertaken.

Indications and contraindications for vaccines used in the Expanded Programme on Immunization

The aim of the Expanded Programme on Immunization is to reduce morbidity and mortality from six diseases that can be prevented by immunization. In many countries the immunization coverage is still less than optimal; one of the reasons for this is the fact that frequently health workers are faced with long lists of contraindications to immunization.The present review discusses the risks of adverse reactions after immunization and compares these risks with the complication rates following natural disease. It is concluded that the decision to withhold the benefits of immunization from an eligible child should not be taken lightly, particularly in areas where access to immunization services is limited and the incidence of the vaccine-preventable diseases is still high.Malnutrition should be a prime indication for immunization. Low-grade fever, mild respiratory infection, or diarrhoea should not be considered a contraindication to immunization. Measles immunization of children who have to be admitted to hospital has been shown to reduce the overall mortality rates in paediatric wards. It is recommended that all countries should formulate their own national policy, carefully considering the risks of disease as well as the benefits and potential risks of immunization.