Elevated levels of maternal anti-tetanus toxin antibodies do not suppress the immune response to a Haemophilus influenzae type b polyribosylphosphate-tetanus toxoid conjugate vaccine.

Reported are the effects of elevated levels of anti-tetanus antibodies on the safety and immune response to a Haemophilus influenzae type b polyribosylphosphate (PRP)-tetanus toxoid conjugate (PRP-T) vaccine. A group of Thai infants (n = 177) born to women immunized against tetanus during pregnancy were vaccinated with either a combined diphtheria-tetanus-pertussis (DTP) PRP-T vaccine or DTP and a PRP-conjugate vaccine using Neisseria meningitidis group B outer-membrane proteins as a carrier (PedVax HIB). Although most infants possessed high titres (> 1 IU/ml) of anti-tetanus antibodies, the DTP-PRP-T combined vaccine engendered an excellent antibody response to all vaccine components. In both vaccine groups > 98% of infants attained anti-PRP antibody titres > or = 0.15 microgram/ml. The geometric mean anti-PRP antibody titres were 5.41 micrograms/ml and 2.1 micrograms/ml for infants immunized with three doses of PRP-T versus two doses of PedVax HIB vaccines, respectively (P < 0.005). Similarly, the proportion of infants who achieved titres > or = 1 microgram/ml was higher in the PRP-T group (87.8%) than in the group immunized with PedVax HIB (74.2%) (P = 0.036). A subgroup analysis showed that there was no significant difference in the anti-PRP antibody response for infants exhibiting either < 1 IU of anti-tetanus antibody per millilitre or > or = 1 IU/ml at baseline. These finding indicate that pre-existing anti-carrier antibody does not diminish the immune response to the PRP moiety. All infants possessed protective levels of anti-D and anti-T antibody levels after immunization.

PIP: Reported are the effects of elevated levels of anti-tetanus antibodies on the safety and immune response to Haemophilus influenzae type b polyribosylphosphate (PRP)-tetanus toxoid conjugate (PRP-T) vaccine. A group of Thai infants (n = 177) born to women immunized against tetanus during pregnancy were vaccinated with either a combined diptheria-tetanus-pertussis (DTP) PRP-T vaccine or DTP and a PRP-conjugate vaccine using Neisseria meningitidis group B outer-membrane proteins as a carrier (PedVax HIB). Although most infants possessed high titers (1 IU/ml) of anti-tetanus antibodies, the DTP-PRP-T combined vaccine engendered an excellent antibody response to all vaccine components. In both vaccine groups, 98% of infants attained anti-PRP antibody titers of 0.15 mcg/ml or higher. The geometric mean anti-PRP antibody titers were 5.41 mcg/ml and 2.1 mcg/ml for infants immunized with 3 doses of PRP-T vs. 2 doses of PedVax HIB vaccines, respectively (P 0.005). Similarly, the proportion of infants who achieved titers of 1 mcg/ml or higher was greater in the PRP-T group (87.8%) than in the group immunized with PedVax HIB (74.2%) (P = 0.036). A group analysis showed that there was no significant difference in the anti-PRP antibody response for infants exhibiting either less than 1 IU/ml of anti-tetanus antibody or 1 or more IU/ml at baseline. These findings indicate that pre-existing anti-carrier antibody does not diminish the immune response to the PRP moiety. All infants possessed protective levels of anti-D and anti-T levels after immunization.

Safety and immunogenicity of a Haemophilus influenzae type B polysaccharide-tetanus toxoid conjugate vaccine combined with diphtheria, tetanus and pertussis vaccines in Thai infants.

A randomized, open, multicenter trial was conducted to determine the safety and immunogenicity of a Haemophilus influenzae type b polysaccharide-tetanus toxoid (PRP-T) conjugate vaccine combined with tetanus, diphtheria and pertussis (DTP) vaccine in 271 Thai infants born to mothers immunized against tetanus during pregnancy. Infants were immunized at approximately 2, 4 and 6 months of age with these vaccines. To determine if elevated levels of anti-tetanus toxin antibodies suppressed the anti-PRP antibody response, a second group of infants were immunized with PRP complexed with outer membrane proteins of Neisseria meningitidis (Pedvax HIB) in one limb at 2 and 4 months of age and DTP vaccine in the other limb at 2, 4 and 6 months of age. A third group of infants received only DTP vaccine at 2, 4 and 6 months of age. The occurrence of both local and systemic adverse reactions were comparable in all 3 groups. The geometric mean anti-tetanus antibody titer was > 1 IU/ml at baseline. Approximately 1 month after the administration of the third dose of vaccine, 98.5%, 99.3% and 9.7% of the children immunized with DTP+Pedvax HIB, DTP-PRP-T or DTP possessed > or = 0.15 microgram of anti-PRP antibody per ml. No child in the DTP group achieved > or = 1 microgram/ml while 74.2% and 89.3% did so after immunization with DTP+Pedvax HIB, or DTP-PRP-T, respectively (p < 0.05). Immune responses to diphtheria, tetanus and pertussis antigens were similar in all vaccine groups. These results demonstrate that elevated tetanus antibody titers do not diminish the anti-PRP antibody response following immunization with a PRP-T conjugate combined with DTP vaccine.

Perinatal HIV infections in Thailand.

A collaborative study group of researchers from seven hospitals from all regions of Thailand was formed to collect information on children born to HIV-infected mothers since the beginning of the first hospital case until the end of June 1994. The study conducted to verify the status of perinatal transmission of HIV infection in Thailand showed a rapid increase in HIV seropositivity among Thai mothers with vertical transmission rates varying between 25% in Rayong and 42% in Chiang Rai Hospitals, respectively. The majority of children with symptomatic HIV infection had clinical presentations of delayed growth development, pneumonia, diarrhea, oral candidiasis, lymphadenopathy, hepato-splenomegaly. Cases of Penicillium marneffei infection were found only at Chiang Rai Prachanukroh Hospital. The ages at which diagnosis of HIV disease was made were mostly within the first year of life. One third of children with AIDS died during the period of study.