OBJECTIVE. The American Academy of Pediatrics recommends immunization of preterm infants at 2 months' chronological age with diphtheria-tetanus-acellular pertussis vaccine, regardless of birth weight and gestational age. Several investigators have reported an increased incidence of cardiorespiratory events in preterm infants after immunization. Consequently, many primary care providers do not adhere to American Academy of Pediatrics guidelines. The purpose of this study was to reexamine the relationship between diphtheria-tetanus-acellular pertussis and cardiorespiratory events in preterm infants by using a random control study design and an objective assessment of cardiorespiratory events.

METHODS. Ten hospitals enrolled 191 infants who were born at <37 weeks' gestational age at 56 to 60 days' chronological age. Infants were randomly assigned to a group that received diphtheria-tetanus-acellular pertussis immunization (n = 93) or a control group that did not (n = 98). Recording monitors were used continuously during the next 48 hours to document prolonged apnea and prolonged bradycardia. The presence and number of episodes during the 48-hour period were compared between groups by using χ2 and t tests.

RESULTS. In the diphtheria-tetanus-acellular pertussis group, 16.1% experienced at least 1 episode of prolonged apnea compared with 20.4% of control infants. One or more prolonged bradycardia events occurred in 58.1% of immunized infants and 56.1% of the control infants. The frequency of episodes was not significantly different between groups. The immunization group and the control group each had an average of 0.5 episodes of prolonged apnea. The mean number of prolonged bradycardia episodes was 2.6 in the immunization group and 2.7 in the control group.

CONCLUSIONS. Preterm infants who received diphtheria-tetanus-acellular pertussis at 2 months after birth were no more likely to experience prolonged apnea and bradycardia than were control infants. This study supports the American Academy of Pediatrics recommendation regarding diphtheria-tetanus-acellular pertussis immunization at 2 months of age for preterm infants.

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