Antibody response of low birth weight infants to Haemophilus influenzae type b polyribosylribitol phosphate-outer membrane protein conjugate vaccine.
OBJECTIVE
To evaluate the effectiveness in low birth weight (LBW) infants of the currently recommended immunization schedule for conjugated Haemophilus influenzae type b (HIB) vaccine.


METHODS
We quantified antibody responses in 36 preterm infants with a mean birth weight of 1060 g and a mean gestational age of 28 weeks. Infants were immunized with 0.5 mL of HIB vaccine at 2 and 4 months' postnatal age. Specific HIB antibodies were quantified on cord blood, immediately before each immunization and 2 months after the last immunization.


RESULTS
Even though the geometric mean titers increased significantly during the study period, they were still markedly lower than values reported in term infants. After the second immunization, only 24 infants (67%) attained antibody concentrations of more than 0.25 micrograms/mL, defined as seropositivity. Also, only 53% of infants achieved antibody concentrations of more than 1.0 micrograms/mL compared with 92% as reported in term infants. Stepwise logistic regression identified gestational age of 27 weeks or less and the amount of intravenous immunoglobulin received as the significant variables influencing the antibody response after the first immunization. The incidence of side effects was negligible.


CONCLUSIONS
We conclude that LBW infants, and especially those born at 27 or less weeks' gestation, do not respond as effectively to the HIB vaccine. We speculate that reevaluation of the current immunization schedule may be required for very LBW infants.
Munoz
A
A
Division of Neonatology, Albert Einstein Medical Center, Philadelphia, PA 19141, USA.
Salvador
A
A
Brodsky
N L
NL
Arbeter
A M
AM
Porat
R
R
D000907:Antibodies, Bacterial / Q000096:biosynthesis*; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology*; D001803:Blood Transfusion; D001997:Bronchopulmonary Dysplasia / Q000276:immunology; D005260:Female; D005312:Fetal Blood / Q000276:immunology; D005865:Gestational Age; D018073:Haemophilus Vaccines / Q000276:immunology*; D006193:Haemophilus influenzae / Q000145:classification / Q000276:immunology*; D006801:Humans; D007115:Immunization Schedule; D016756:Immunoglobulins, Intravenous / Q000276:immunology; D007230:Infant, Low Birth Weight / Q000276:immunology*; D007231:Infant, Newborn; D008297:Male; D011134:Polysaccharides / Q000276:immunology*; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D014611:Vaccination; D018074:Vaccines, Conjugate
D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D018073:Haemophilus Vaccines; D016756:Immunoglobulins, Intravenous; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; D018074:Vaccines, Conjugate; C008984:polyribitol phosphate