Additional Hib Immunization May Benefit Preterm Steroid-Treated Infants
NEW YORK (Reuters Health) Jan 07 - Although immunization with a fourth
Haemophilus influenza type b (Hib) vaccine does not increase antibody levels in
preterm steroid-treated infants, it does appear to improve the avidity of the
antibodies generated, according to a recent report.
The typical Hib vaccine schedule for term infants involves three injections
in the first few months of life. Previous reports have shown, however, that this
regimen may not achieve an adequate antibody response in preterm infants treated
with steroids.
Dr. P. Clarke, from Hope Hospital in Salford, UK, and colleagues hypothesized
that administration of a fourth vaccine may improve the antibody response of
such infants. The researchers' findings are published in the January issue of
the Archives of Disease in Childhood: Fetal and Neonatal Edition.
The study involved 12 infants born at less than 30 weeks gestation who had
received dexamethasone for chronic lung disease. Six weeks after completing the
standard Hib vaccine regimen, the infants received a fourth Hib dose.
The fourth immunization was not associated with a significant increase in
anti-PRP antibody levels, the authors note. Moreover, infants who had
subprotective antibody levels prior to the fourth dose continued to have
subprotective levels after the extra dose.
Although the extra dose did not have a beneficial quantitative effect, it was
associated with a qualitative improvement in Hib antibody. Specifically, PRP
specific IgG avidity improved significantly after the fourth immunization.
Based on parental reports, administration of an extra dose was not associated
with any adverse incidents, the investigators point out.
"An additional Hib dose given to recently steroid-treated preterm infants 6
weeks after the primary course does not appear to improve absolute titre of Hib
antibody and cannot be currently recommended," the authors note. Still, "the
avidity increase observed following the extra Hib dose suggests a qualitative
improvement in antibody associated with boosting, and merits further
investigation in a larger study."
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