Ah, more of those sticky individual differences mucking up the works. - SM
NEW YORK (Reuters Health) Mar 05 - Former extremely preterm infants have lower
antibody titers to many vaccine antigens at 7 years than children born at full
term, according to a report in the March issue of Pediatrics. However,
antibody titers are still in the protective range in most of these children.
Dr. Carl T. D'Angio and colleagues, from the University of Rochester, New
York, compared the immune response of 16 former extremely preterm infants and
16 age-matched full-term controls at 7 years. All children had received their
routine childhood immunizations at the appropriate chronological ages. The
researchers measured antibodies to Haemophilus influenzae type b
polyribosylribitol phosphate (Hib-PRP), tetanus, pertussis, diphtheria, polio,
and hepatitis B.
The full-term group had higher antidiphtheria geometric mean titers (GMT)
than the preterm group. Protective diphtheria titers (greater than 0.10 IU/mL)
were found in all of the full term and 13 of the preterm children. Full-term
children had tetanus GMT of 4.22 IU/mL, compared with 1.99 IU/mL in the
preterm group. Protective tetanus titers (greater than 0.01 IU/mL) were found
in all the children.
Pertussis titers were similar in both groups of children. The full-term
group had higher Hib-PRP GMT than the preterm group, at 3.21 mcg/mL and 1.41
mcg/mL, respectively (p = 0.03). "All children had anti-PRP of at least 0.15
mcg/mL," the team notes. Twelve of the16 full-term children and 10 of the 16
preterm children had levels at least 1.0 mcg/mL.
They observed no differences in polio serotype 1 and 2 GMT between groups.
Protective titers were found in all children. The full-term group had polio
serotype 3 GMT of 59 Karber units, compared with 24 Karber units for preterm
children. Protective titers were observed in all full-term children and 12
preterm children.
"Among children who had received hepatitis B vaccine, GMT were similar in
full-term and preterm children...and similar proportions of children...had
protective HBsAb titers (greater than 10 mIU/mL)," Dr. D'Angio and colleagues
report.
Overall, "children who were born extremely prematurely [at 6.5 months or
earlier] still get good levels of antibody (protection) from routine infant
vaccines," Dr. D'Angio told Reuters Health.
"These findings support the American Academy of Pediatrics' general
recommendation to immunize premature infants in the same way as one would
immunize full-term infants," he continued. "However, the fact that premature
infants' antibody levels are still somewhat lower than full-term babies'
levels all the way out to 7 years implies that there may be some important,
basic differences in the immune system if a baby is born early."
"Premature infants are at higher risk from vaccine preventable diseases,"
he added, "so it's particularly important for them to be immunized fully and
on time."
Pediatrics 2002;109:498-504.
