Zulaika Ali

RESPONSE TO IMMUNIZATION IN THE PREMATURE NEWBORN

The human immune system is not fully competent at the time of birth and is even more immature with earlier gestational age at delivery.We are studying the immune response of prematures born at Mt. Hope Hospital, Trinidad to determine the optimal time of immunization. Neonates are divided into four groups based on birth weight. Each group is further subdivided into two subgroups, one immunized 6-8 weeks after birth and the other 6-8 weeks after calculated full term. Immunization includes diphtheria, pertussis tetanus and polio. Immune response is measured by tetanus toxoid antibody and cellular responses.To date, 50 neonates have been entered into the study. Thirty-nine have completed the primary series of three immunizations and 27 have had at least one follow-up sample. Twelve of the neonates were less than 1500g at birth. Eleven of the 12 have had appropriate antibody responses. The baby who did not respond had a high titer of passive maternal antibody at birth (4.2 I.U. /ml) and the absence of response may be related to this. No differences in response have been observed with early and late immunization. Cellular responses to tetanus toxoid were variable. Forty-two percent of babies showed in vitro reactivity to tetanus at birth. However, only 30% were reactive following the primary immunization series. Blastogenic responses to streptococcal antigens fluctuated with the tetanus responses, suggesting no specificity in the blastogenic response in these neonates.